We thank the staff within the Institute of Human Genetics for NGS library preparation and sequencing. We thank Einat Snir for her expertise in preparing genomic library fragments for the Y2H plasmid library made here. This work was supported by National Institutes of Health: NIH R21 EB021870-01A1 and by NSF Research Project Grant: 1517110.

<ol>
	<li>Fields, S., Song, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+genetic+system+to+detect+protein-protein+interactions.">A novel genetic system to detect protein-protein interactions.</a> Nature. 340 (6230), 245-246 (1989).</li><li>Bruckner, A., Polge, C., Lentze, N., Auerbach, D., Schlattner, U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Yeast+two-hybrid,+a+powerful+tool+for+systems+biology.">Yeast two-hybrid, a powerful tool for systems biology.</a> International Journal of Molecular Sciences. 10 (6), 2763-2788 (2009).</li><li>Vidal, M., Fields, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+yeast+two-hybrid+assay:+still+finding+connections+after+25+years.">The yeast two-hybrid assay: still finding connections after 25 years.</a> Nature Methods. 11 (12), 1203-1206 (2014).</li><li>Pashkova, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=DEEPN+as+an+Approach+for+Batch+Processing+of+Yeast+2-Hybrid+Interactions.">DEEPN as an Approach for Batch Processing of Yeast 2-Hybrid Interactions.</a> Cell Reports. 17 (1), 303-315 (2016).</li><li>Rajagopala, S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+the+Protein-Protein+Interactome+Networks+Using+Yeast+Two-Hybrid+Screens.">Mapping the Protein-Protein Interactome Networks Using Yeast Two-Hybrid Screens.</a> Advances in Experimental Medicine and Biology. 883, 187-214 (2015).</li><li>Weimann, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Y2H-seq+approach+defines+the+human+protein+methyltransferase+interactome.">A Y2H-seq approach defines the human protein methyltransferase interactome.</a> Nature Methods. 10 (4), 339-342 (2013).</li><li>Yachie, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pooled-matrix+protein+interaction+screens+using+Barcode+Fusion+Genetics.">Pooled-matrix protein interaction screens using Barcode Fusion Genetics.</a> Molecular Systems Biology. 12 (4), 863 (2016).</li><li>Trigg, S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CrY2H-seq:+a+massively+multiplexed+assay+for+deep-coverage+interactome+mapping.">CrY2H-seq: a massively multiplexed assay for deep-coverage interactome mapping.</a> Nature Methods. , (2017).</li><li>Estojak, J., Brent, R., Golemis, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Correlation+of+two-hybrid+affinity+data+with+in+vitro+measurements.">Correlation of two-hybrid affinity data with in vitro measurements.</a> Molecular and Cellular Biology. 15 (10), 5820-5829 (1995).</li><li>Rajagopala, S. V., Hughes, K. T., Uetz, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Benchmarking+yeast+two-hybrid+systems+using+the+interactions+of+bacterial+motility+proteins.">Benchmarking yeast two-hybrid systems using the interactions of bacterial motility proteins.</a> Proteomics. 9 (23), 5296-5302 (2009).</li><li>James, P., Halladay, J., Craig, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genomic+libraries+and+a+host+strain+designed+for+highly+efficient+two-hybrid+selection+in+yeast.">Genomic libraries and a host strain designed for highly efficient two-hybrid selection in yeast.</a> Genetics. 144 (4), 1425-1436 (1996).</li><li>Barbas, C. F., Burton, D. R., Scott, J. K., Silverman, G. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitation+of+DNA+and+RNA.">Quantitation of DNA and RNA.</a> CSH Protoc. 2007, pdb ip47 (2007).</li><li>Sambrook, J., Russell, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SDS-Polyacrylamide+Gel+Electrophoresis+of+Proteins.">SDS-Polyacrylamide Gel Electrophoresis of Proteins.</a> Cold Spring Harbor Protocols. 2006 (4), (2006).</li><li>Towbin, H., Staehelin, T., Gordon, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophoretic+transfer+of+proteins+from+polyacrylamide+gels+to+nitrocellulose+sheets:+procedure+and+some+applications.">Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications.</a> Proceedings of the National Academy of Sciences USA. 76 (9), 4350-4354 (1979).</li><li>Alegria-Schaffer, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Western+blotting+using+chemiluminescent+substrates.">Western blotting using chemiluminescent substrates.</a> Methods in Enzymology. 541, 251-259 (2014).</li><li>Lee, P. Y., Costumbrado, J., Hsu, C. Y., Kim, Y. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Agarose+gel+electrophoresis+for+the+separation+of+DNA+fragments.">Agarose gel electrophoresis for the separation of DNA fragments.</a> Journal of Visualized Experiments. (62), (2012).</li><li>Harper, J. W., Adami, G. R., Wei, N., Keyomarsi, K., Elledge, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+p21+Cdk-interacting+protein+Cip1+is+a+potent+inhibitor+of+G1+cyclin-dependent+kinases.">The p21 Cdk-interacting protein Cip1 is a potent inhibitor of G1 cyclin-dependent kinases.</a> Cell. 75 (4), 805-816 (1993).</li></ol>

The authors have nothing to disclose

Here we provide a guide for how to perform Y2H assays in batch using optimized methods. There are a few critical steps in the procedure to help ensure that the population of yeast that would be placed under selection is representative of the starting library and that enough of the starting yeast population is used to undergo selection to limit variability. Importantly, these benchmarks are relatively easy to achieve alongside adapting the methods and materials for a traditional Y2H assay, thus making this approach access...

A complete understanding of cell biological processes relies on finding the protein interaction networks that underlie their molecular mechanisms. One approach to identify protein interactions is the yeast 2-hybrid (Y2H) assay, which works by assembling a functioning chimeric transcription factor once two protein domains of interest bind to one another1. A typical Y2H screen is performed by creating a population of yeast that houses both a library of plasmids encoding interacting proteins fused to a transcriptional activator (e.g., &#39;prey&#39; fusion protein) and a given &#39;bait&#39; plasmid comprised of the protein of interest fused to a DNA binding domain (e.g., the Gal4 DNA-binding domain that binds to the Gal4-upstream activating sequence). One of the main advantages of the Y2H approach is that it is relatively easy and inexpensive to conduct in a typical laboratory equipped for routine molecular biological work2. However, when traditionally performed, a user samples individual colonies that arise upon selection for a positive Y2H interaction. This severely limits the number of library &#39;prey&#39; clones that can be surveyed. This problem is compounded when the abundance of a particular interacting prey is very high relative to the others, diminishing the chance of detecting interaction from low abundance prey plasmids.
One solution for using the Y2H principle in comprehensive coverage of the proteome is the use of a matrix-formatted approach wherein an array containing known individual prey plasmids can be digitally interrogated. However, such an approach requires an infrastructure that is not readily accessible or cost-effective to individual investigators who are interested in defining the interactome of a small number of proteins or domains3. In addition, very complex prey libraries that may encode multiple fragments of interacting proteins would expand the size of such matrix arrays to impractical sizes. An alternative is to perform assays with complex libraries in batches and assess the presence of interacting clones using massive parallel high-throughput sequencing4. This can be applied to assay the presence of prey plasmids that arise in multiple colonies using a typical Y2H formatted approach in which yeast cells housing an interacting pair of fusion proteins are allowed to grow on a plate5,6. This general idea can be accentuated to increase query of both multiple bait and prey components at the same time7,8.
Still, many investigations require an easier yet more focused effort on just a few protein &#39;baits&#39; and can benefit more by an exhaustive and semi-quantitative query of a single complex prey library. We have developed and validated an approach to perform wide-scale protein interaction studies using a Y2H principle in batch format4. This uses the rate of expansion of a particular prey plasmid as a proxy for the relative strength of Y2H interaction9. Deep sequencing of all plasmids within a population subjected to normal growth or selective growth conditions produces a complete map of clones that yield strong and weak Y2H interactions. The repertoire of interactors can be obtained and directly compared across multiple bait plasmids. The resulting workflow termed DEEPN (Dynamic Enrichment for Evaluation of Protein Networks) can thus be used to identify differential interactomes from the same prey libraries to identify proteins, allowing comparison between one protein vs. another.
Here, we demonstrate DEEPN and introduce improvements in the laboratory methods that facilitate its use, which are outlined in Figure 1. Significant improvements include:
Generation of prey yeast populations. One of the key requirements of DEEPN is generating populations of yeast with different bait plasmids that have the same distribution of the plasmid prey libraries. Equivalent baseline populations of the prey plasmid library are essential for making accurate comparisons between the interactomes of different baits. This is best achieved when a library plasmid is already housed in a haploid yeast population and moving a given bait plasmid into that population is achieved by mating to produce a diploid. Here, we provide a clear guide in how to make such populations using commercial libraries housed in haploid yeast. Although we found methods that generate a high number of diploids, the overall mating efficiency of these commercial library-containing yeast strains was low. Therefore, we constructed a new strain that can house prey libraries that yields far more diploids per mating reaction.
New set of bait plasmids. Many current plasmids that express &#39;bait&#39; fusion proteins comprised of the protein of interest and a DNA-binding domain are 2&#181;-based, allowing them to amplify their copy number. This copy number can be quite variable in the population and lead to variability in the Y2H transcriptional response. This in turn could skew the ability to gauge the strength of a given protein interaction based on the growth response of cells under selection. This can be partly address by using a low copy plasmid, some of which have been previously described such as the commercially available pDEST3210. We constructed a new bait plasmid (pTEF-GBD) that produces Gal4-DNA-binding domain fusion proteins within a TRP1 centromere-based low copy plasmid carrying the Kanr resistance gene that also allows cloning of bait fragments both upstream and downstream of the Gal4 DNA-binding domain.
New High-Density Y2H fragment library. We constructed a new plasmid to house Y2H prey libraries and used it to build a highly complex Y2H library made of randomly sheared fragments of genomic DNA from Saccharomyces cerevisiae. Sequence analysis showed that this library had over 1 million different elements, far more complex than previously described yeast genomic Y2H plasmid libraries11. With this new library, we were able to show that the DEEPN workflow is robust enough to accommodate complex libraries with many different plasmids in a manner that is reliable and reproducible.

<table>
	<tbody>
		<tr>
			<td>Illumina HiSeq 4000</td>
			<td>Illumina</td>
			<td></td>
			<td>deep sequencing platform</td>
		</tr>
		<tr>
			<td>Monoclonal anti-HA antibodies</td>
			<td>Biolegend</td>
			<td>901514</td>
			<td>Primary Antibody to detect expression of HA in pGal4AD constructs</td>
		</tr>
		<tr>
			<td>Polyclonal anti-myc antibodies</td>
			<td>QED Biosciences Inc</td>
			<td>18826</td>
			<td>Primary Antibody to detect expression of MYC in pTEF-GBD constructs</td>
		</tr>
		<tr>
			<td>NarI</td>
			<td>New England BioLabs</td>
			<td>R0191S</td>
			<td></td>
		</tr>
		<tr>
			<td>EcoRI-HF</td>
			<td>New England BioLabs</td>
			<td>R3101S</td>
			<td></td>
		</tr>
		<tr>
			<td>BamHI-HF</td>
			<td>New England BioLabs</td>
			<td>R3236S</td>
			<td></td>
		</tr>
		<tr>
			<td>XhoI</td>
			<td>New England BioLabs</td>
			<td>R0146S</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyethylene Glycol 3350, powder</td>
			<td>J.T. Baker</td>
			<td>U2211-08</td>
			<td></td>
		</tr>
		<tr>
			<td>Salmon Sperm DNA</td>
			<td>Trevigen, Inc sold by Fisher Scientific</td>
			<td>50-948-286</td>
			<td>carrier DNA for yeast transformation section 3.2.1.</td>
		</tr>
		<tr>
			<td>Kanamycin Monosulfate</td>
			<td>Research Products International</td>
			<td>K22000</td>
			<td></td>
		</tr>
		<tr>
			<td>LE Agarose</td>
			<td>GeneMate</td>
			<td>E-3120-500</td>
			<td>used for making DNA agarose gels</td>
		</tr>
		<tr>
			<td>Sodium Chloride</td>
			<td>Research Products International</td>
			<td>S23025</td>
			<td></td>
		</tr>
		<tr>
			<td>Tryptone</td>
			<td>Research Products International</td>
			<td>T60060</td>
			<td></td>
		</tr>
		<tr>
			<td>D-Sorbitol</td>
			<td>Research Products International</td>
			<td>S23080</td>
			<td></td>
		</tr>
		<tr>
			<td>Lithium Acetate Dihydrate</td>
			<td>MP Biomedicals</td>
			<td>155256</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcium Chloride</td>
			<td>ThermoFisher</td>
			<td>C79</td>
			<td></td>
		</tr>
		<tr>
			<td>EDTA Sodium Salt</td>
			<td>Research Products International</td>
			<td>E57020</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast Extract Powder</td>
			<td>Research Products International</td>
			<td>Y20020</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast Nitrogen Base (ammonium sulfate) w/o amino acids</td>
			<td>Research Products International</td>
			<td>Y20040</td>
			<td></td>
		</tr>
		<tr>
			<td>CSM-Trp-Leu+40ADE</td>
			<td>Formedium</td>
			<td>DCS0789</td>
			<td></td>
		</tr>
		<tr>
			<td>CSM-Trp-Leu-His+40ADE</td>
			<td>Formedium</td>
			<td>DCS1169</td>
			<td></td>
		</tr>
		<tr>
			<td>CSM-Leu-Met</td>
			<td>Formedium</td>
			<td>DCS0549</td>
			<td></td>
		</tr>
		<tr>
			<td>CSM-Trp-Met</td>
			<td>Bio 101, Inc</td>
			<td>4520-922</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Methionine</td>
			<td>Formedium</td>
			<td>DOC0168</td>
			<td></td>
		</tr>
		<tr>
			<td>Adenine</td>
			<td>Research Products International</td>
			<td>A11500</td>
			<td></td>
		</tr>
		<tr>
			<td>D-(+)-Glucose</td>
			<td>Research Products International</td>
			<td>G32045</td>
			<td></td>
		</tr>
		<tr>
			<td>Bacto Agar</td>
			<td>BD</td>
			<td>214010</td>
			<td>used for making media plates in section 1</td>
		</tr>
		<tr>
			<td>Peptone</td>
			<td>Research Products International</td>
			<td>P20240</td>
			<td></td>
		</tr>
		<tr>
			<td>3-amino-1,2,4 Triazole</td>
			<td>Sigma</td>
			<td>A8056</td>
			<td></td>
		</tr>
		<tr>
			<td>2-Mercaptoehanol (BME)</td>
			<td>Sigma-Aldrich</td>
			<td>M6250</td>
			<td></td>
		</tr>
		<tr>
			<td>Zymolyase 100T</td>
			<td>USBiological</td>
			<td>Z1004</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium phosphate dibasic</td>
			<td>Sigma</td>
			<td>P8281</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenol:Chloroform:IAA</td>
			<td>Ambion</td>
			<td>AM9732</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium Acetate</td>
			<td>Sigma-Aldrich</td>
			<td>238074</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Decon Laboratories, INC</td>
			<td>2716</td>
			<td></td>
		</tr>
		<tr>
			<td>RNAse A</td>
			<td>ThermoFisher</td>
			<td>EN0531</td>
			<td></td>
		</tr>
		<tr>
			<td>Urea</td>
			<td>Research Products International</td>
			<td>U20200</td>
			<td></td>
		</tr>
		<tr>
			<td>SDS</td>
			<td>Research Products International</td>
			<td>L22010</td>
			<td></td>
		</tr>
		<tr>
			<td>glycerol</td>
			<td>Sigma Aldrich</td>
			<td>G5516</td>
			<td></td>
		</tr>
		<tr>
			<td>Tris-HCl</td>
			<td>Gibco</td>
			<td>15506-017</td>
			<td></td>
		</tr>
		<tr>
			<td>bromophenol blue</td>
			<td>Amresco</td>
			<td>449</td>
			<td></td>
		</tr>
		<tr>
			<td>Gibson Assembly Cloning Kit</td>
			<td>New England Biolabs</td>
			<td>E5510S</td>
			<td>Rapid assembly method for cloning of plasmids in section 2</td>
		</tr>
		<tr>
			<td>NEBNext High-Fidelity 2x PCR Master Mix</td>
			<td>New England Biolabs</td>
			<td>M0541S</td>
			<td>Used for amplification of products for Gibson Assembly in Section 2.3 as well assample preparation for DEEPN deep sequencing in section 6.2.1</td>
		</tr>
		<tr>
			<td>Ethidium Bromide</td>
			<td>Amresco</td>
			<td>0492-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>QIAquick PCR purification kit</td>
			<td>Qiagen</td>
			<td>28104</td>
			<td>Used for purification of pcr products in section 6.2.3</td>
		</tr>
		<tr>
			<td>Qiaquick DNA Gel Extraction Kit</td>
			<td>Qiagen</td>
			<td>28704</td>
			<td>Used for purification of digested pTEF-GBD in section 2.1</td>
		</tr>
		<tr>
			<td>KAPA Hyper Prep kit</td>
			<td>KAPA Biosystems</td>
			<td>KK8500</td>
			<td>preparation kit for deep sequencing</td>
		</tr>
		<tr>
			<td>Codon optimization</td>
			<td>http://www.jcat.de</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Codon optimization</td>
			<td>https://www.idtdna.com/CodonOpt</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>gBlocks</td>
			<td>Integrated DNA Technologies</td>
			<td></td>
			<td>DNA fragments used for cloning in Section 2.2</td>
		</tr>
		<tr>
			<td>Strings</td>
			<td>Thermofisher</td>
			<td></td>
			<td>DNA fragments used for cloning in Section 2.2</td>
		</tr>
		<tr>
			<td>GenCatch Plasmid DNA mini-prep Kit</td>
			<td>EPOCH Life Sciences</td>
			<td></td>
			<td>Used to prepare quantities of DNA in Section 2.3</td>
		</tr>
		<tr>
			<td>Covaris E220</td>
			<td>Covaris</td>
			<td></td>
			<td>high performance ultra-sonicator in section 7</td>
		</tr>
		<tr>
			<td>oligo nucelotide 5&#8217;- CGGTCTT 
			CAATTTCTCAAGTTTCAG -3&#8217;</td>
			<td>Integrated DNA Technologies or Thermofisher</td>
			<td></td>
			<td>used for pcr amplification and sequencing 5&#39; insert pTEF-GBD during plasmid construction</td>
		</tr>
		<tr>
			<td>oligo nucelotide 5&#8217;-GAGTAACG 
			ACATTCCCAGTTGTTC-3&#8217;</td>
			<td>Integrated DNA Technologies or Thermofisher</td>
			<td></td>
			<td>used for pcr amplification and sequencing 5&#39; insert pTEF-GBD during plasmid construction</td>
		</tr>
		<tr>
			<td>oligo nucelotide 5&#8217;-CACCGTAT 
			TTCTGCCACCTCTTCC-3&#8217;</td>
			<td>Integrated DNA Technologies or Thermofisher</td>
			<td></td>
			<td>used for pcr amplification and sequencing 3&#39; insert pTEF-GBD during plasmid construction</td>
		</tr>
		<tr>
			<td>oligo nucelotide 5&#8217;-GCAACCGC 
			ACTATTTGGAGCGCTG-3&#8217;</td>
			<td>Integrated DNA Technologies or Thermofisher</td>
			<td></td>
			<td>used for pcr amplification and sequencing 3&#39; insert pTEF-GBD during plasmid construction</td>
		</tr>
		<tr>
			<td>oligonucleotide 5&#8217;-GTTCCGATG 
			CCTCTGCGAGTG-3&#8217;</td>
			<td>Integrated DNA Technologies or Thermofisher</td>
			<td></td>
			<td>5&#39; Pimer used for insert amplification of pGAL4AD</td>
		</tr>
		<tr>
			<td>oligonucelotide 5&#8217;-GCACATGCT 
			AGCGTCAAATACC-3&#8217;</td>
			<td>Integrated DNA Technologies or Thermofisher</td>
			<td></td>
			<td>3&#39; Pimer used for insert amplification of pGAL4AD</td>
		</tr>
		<tr>
			<td>oligonucelotide 5&#8217;-ACCCAAGCA 
			GTGGTATCAACG-3&#8217;</td>
			<td>Integrated DNA Technologies or Thermofisher</td>
			<td></td>
			<td>5&#39; Pimer used for insert amplification of pGADT7</td>
		</tr>
		<tr>
			<td>oligonucelotide 5&#8217;- TATTTAGA 
			AGTGTCAACAACGTA -3&#8217;</td>
			<td>Integrated DNA Technologies or Thermofisher</td>
			<td></td>
			<td>3&#39; Pimer used for insert amplification of pGADT7</td>
		</tr>
		<tr>
			<td>PJ69-4A MatA yeast strain</td>
			<td>http://depts.washington.edu/yeastrc/ James P, Halladay J, Craig EA: Genomic Libraries and a host strain designed for highly efficient two-hybrid selection in yeast. GENETICS 1996 144:1425-1436</td>
			<td></td>
			<td>MATA leu2-3,112 ura3-52 trp1-901 his3-200 gal4D, gal80D, GAL-ADE2 lys2::GAL1-HIS3 met2::GAL7</td>
		</tr>
		<tr>
			<td>pTEF-GBD</td>
			<td>Dr. Robert Piper Lab</td>
			<td></td>
			<td>Gal4-DNA binding doimain expression plasmid</td>
		</tr>
		<tr>
			<td>PLY5725 MATalpha yeast strain</td>
			<td>Dr. Robert Piper Lab</td>
			<td></td>
			<td>MATalpha his3&#8710;1 leu2&#8710;0 lys2&#8710;0 ura3&#8710;0 gal4&#8710; trp1&#8710; Gal80&#8710;</td>
		</tr>
		<tr>
			<td>pGal4AD (pPL6343)</td>
			<td>Dr. Robert Piper Lab</td>
			<td></td>
			<td>Gal4-activation domain expression plasmid</td>
		</tr>
		<tr>
			<td>100 mm petri dishes</td>
			<td>Kord-Vallmark sold by VWR</td>
			<td>2900</td>
			<td></td>
		</tr>
		<tr>
			<td>125 mL PYREX Erlenmeyer flask</td>
			<td>Fisher Scientific</td>
			<td>S63270</td>
			<td></td>
		</tr>
		<tr>
			<td>250 mL PYREX Erlenmeyer flask</td>
			<td>Fisher Scientific</td>
			<td>S63271</td>
			<td></td>
		</tr>
		<tr>
			<td>1,000 mL PYREX Erlenmeyer flask</td>
			<td>Fisher Scientific</td>
			<td>S63274</td>
			<td></td>
		</tr>
		<tr>
			<td>2,000 mL PYREX Erlenmeyer flask</td>
			<td>Fisher Scientific</td>
			<td>S63275</td>
			<td></td>
		</tr>
		<tr>
			<td>20 X 150 mm Disposable Culture Tube</td>
			<td>Thermofisher</td>
			<td>14-961-33</td>
			<td></td>
		</tr>
		<tr>
			<td>pipet-aid</td>
			<td>Drummond</td>
			<td>4-000-100</td>
			<td></td>
		</tr>
		<tr>
			<td>5 mL Serological Pipette</td>
			<td>Denville</td>
			<td>P7127</td>
			<td></td>
		</tr>
		<tr>
			<td>10 mL Serological Pipette</td>
			<td>Denville</td>
			<td>P7128</td>
			<td></td>
		</tr>
		<tr>
			<td>25 mL Serological Pipette</td>
			<td>Denville</td>
			<td>P7129</td>
			<td></td>
		</tr>
		<tr>
			<td>1,000 mL PYREX Griffin Beaker</td>
			<td>Fisher Scientific</td>
			<td>02-540P</td>
			<td></td>
		</tr>
		<tr>
			<td>1,000 mL PYREX Reuasable Media Storage Bottle</td>
			<td>Fisher Scientific</td>
			<td>06-414-1D</td>
			<td></td>
		</tr>
		<tr>
			<td>1,000 mL graduated cylinder</td>
			<td>Fisher Scientific</td>
			<td>08-572-6G</td>
			<td></td>
		</tr>
		<tr>
			<td>SpectraMax 190</td>
			<td>Molecular Devices</td>
			<td></td>
			<td>used to measure the Optical Density of cells</td>
		</tr>
		<tr>
			<td>NanoDrop 2000</td>
			<td>Thermo Scientific</td>
			<td>ND-2000</td>
			<td>Spectrophotometer used to quantify amount of DNA</td>
		</tr>
		<tr>
			<td>Electronic UV transilluminator</td>
			<td>Ultra Lum</td>
			<td>MEB 20</td>
			<td>used to visualize DNA in an Ethidium Bromide agarose gel</td>
		</tr>
		<tr>
			<td>P1000 Gilson PIPETMAN</td>
			<td>Fisher Scientific</td>
			<td>F123602G</td>
			<td></td>
		</tr>
		<tr>
			<td>P200 Gilson PIPETMAN</td>
			<td>Fisher Scientific</td>
			<td>F123601G</td>
			<td></td>
		</tr>
		<tr>
			<td>P20 Gilson PIPETMAN</td>
			<td>Fisher Scientific</td>
			<td>F123600G</td>
			<td></td>
		</tr>
		<tr>
			<td>P10 Gilson PIPETMAN</td>
			<td>Fisher Scientific</td>
			<td>F144802G</td>
			<td></td>
		</tr>
		<tr>
			<td>1250 &#181;L Low Retention Pipette Tips</td>
			<td>GeneMate</td>
			<td>P-1236-1250</td>
			<td></td>
		</tr>
		<tr>
			<td>200 &#181;LLow Retention Pipette Tips</td>
			<td>VWR</td>
			<td>10017-044</td>
			<td></td>
		</tr>
		<tr>
			<td>10 &#181;L XL Low Retention Pipette Tips</td>
			<td>VWR</td>
			<td>10017-042</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL conical tube</td>
			<td>VWR</td>
			<td>490001-627</td>
			<td></td>
		</tr>
		<tr>
			<td>15 mL conical tube</td>
			<td>VWR</td>
			<td>490001-621</td>
			<td></td>
		</tr>
		<tr>
			<td>cell scraper</td>
			<td>Denville Scientific</td>
			<td>TC9310</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 mL Microcentrifuge tubes</td>
			<td>USA Scientific</td>
			<td>1615-5500</td>
			<td></td>
		</tr>
		<tr>
			<td>HCl</td>
			<td>Fluka Analytical</td>
			<td>318949-1L</td>
			<td></td>
		</tr>
		<tr>
			<td>NaOH</td>
			<td>J.T. Baker</td>
			<td>5674-02</td>
			<td></td>
		</tr>
		<tr>
			<td>Wooden applicators</td>
			<td>Solon Care</td>
			<td>55900</td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf microcentrifuge 5424</td>
			<td>Fisher Scientific</td>
			<td>05-400-005</td>
			<td>microcentrifuge</td>
		</tr>
		<tr>
			<td>Sorvall ST16R</td>
			<td>Thermo Fisher Scientific</td>
			<td>75004381</td>
			<td>benchtop centrifuge</td>
		</tr>
		<tr>
			<td>Amersham ECL Rabbit IgG, HRP-linked whole Ab (from donkey)</td>
			<td>GE Healthcare</td>
			<td>NA934-1ML</td>
			<td>Secondary Antibody</td>
		</tr>
		<tr>
			<td>Amersham ECL Mouse IgG, HRP-linked whole Ab (from sheep)</td>
			<td>GE Healthcare</td>
			<td>NA931-1ML</td>
			<td>Secondary Antibody</td>
		</tr>
		<tr>
			<td>SuperSignal West Pico Chemiluminescent Substrate</td>
			<td>Thermo Fisher Scientific</td>
			<td>34080</td>
			<td>ECL detection solution</td>
		</tr>
		<tr>
			<td>Isotemp Incubator</td>
			<td>Thermo Fisher Scientific</td>
			<td></td>
			<td>Incubator</td>
		</tr>
		<tr>
			<td>Mutitron 2</td>
			<td>INFORS HT</td>
			<td></td>
			<td>Shaking incubator</td>
		</tr>
		<tr>
			<td>Isotemp Digital-Control Water Bath Model 205</td>
			<td>Fisher Scientific</td>
			<td></td>
			<td>water bath</td>
		</tr>
		<tr>
			<td>Y2H mouse cDNA library in Y187 (pan tissue)</td>
			<td>Clontech</td>
			<td>630482</td>
			<td>commercially available cDNA Library</td>
		</tr>
		<tr>
			<td>Y2H mouse cDNA library in Y187 (mouse brain)</td>
			<td>Clontech</td>
			<td>630488</td>
			<td>commercially available cDNA Library</td>
		</tr>
		<tr>
			<td>pGADT7 AD Vector</td>
			<td>Clontech</td>
			<td>630442</td>
			<td>commercially available AD Vector housing many cDNA libraries</td>
		</tr>
		<tr>
			<td>pGBKT7 DNA-BD Vector</td>
			<td>Clontech</td>
			<td>630443</td>
			<td>commercially available DNA-BD Vector</td>
		</tr>
		<tr>
			<td>Biolase DNA Polymerase</td>
			<td>Bioline</td>
			<td>BIO-21042</td>
			<td>DNA polymerase used for section 2.4</td>
		</tr>
		<tr>
			<td>GeneMate GCL-60 Thermal Cycler</td>
			<td>BioExpress</td>
			<td>P-6050-60</td>
			<td>pcr machine</td>
		</tr>
		<tr>
			<td>TempAssure 0.5 mL PCR tubes</td>
			<td>USA Scientific</td>
			<td>1405-8100</td>
			<td></td>
		</tr>
	</tbody>
</table>

a yeast 2-hybrid screen in batch to compare protein interactions

Screening for protein-protein interactions using the yeast 2-hybrid assay has long been an effective tool, but its use has largely been limited to the discovery of high-affinity interactors that are highly enriched in the library of interacting candidates. In a traditional format, the yeast 2-hybrid assay can yield too many colonies to analyze when conducted at low stringency where low affinity interactors might be found. Moreover, without a comprehensive and complete interrogation of the same library against different bait plasmids, a comparative analysis cannot be achieved. Although some of these problems can be addressed using arrayed prey libraries, the cost and infrastructure required to operate such screens can be prohibitive. As an alternative, we have adapted the yeast 2-hybrid assay to simultaneously uncover dozens of transient and static protein interactions within a single screen utilizing a strategy termed DEEPN (Dynamic Enrichment for Evaluation of Protein Networks), which incorporates high-throughput DNA sequencing and computation to follow the evolution of a population of plasmids that encode interacting partners. Here, we describe customized reagents and protocols that allow a DEEPN screen to be executed easily and cost-effectively.

The Y2H assay has been widely used for finding protein:protein interactions and several adaptations and systems have been developed. For the most part, the same considerations that help ensure success with these previous approaches are important for DEEPN. Some of the important benchmarks include: ensuring expression of DNA-binding domain fusion proteins, ensuring a low background of spurious His+ growth in the diploids containing the bait of interest with an empty prey plasmid, a high ma...

Watch this Scientific Journal Video about A Yeast 2-Hybrid Screen in Batch to Compare Protein Interactions at JoVE.com

A Yeast 2-Hybrid Screen in Batch to Compare Protein Interactions

Batch processing of yeast 2-hybrid screens allows for direct comparison of the interaction profiles of multiple bait proteins with a highly complex set of prey fusion proteins. Here, we describe refined methods, new reagents, and how to implement their use for such screens.

Screening for protein-protein interactions using the yeast 2-hybrid assay has long been an effective tool, but its use has largely been limited to the ...

a-yeast-2-hybrid-screen-in-batch-to-compare-protein-interactions

Universidad de Cartagena UDEC

Research

JoVE Journal

Biochemistry

13.2K Views.  University of Iowa. Batch processing of yeast 2-hybrid screens allows for direct comparison of the interaction profiles of multiple bait proteins with a highly complex set of prey fusion proteins. Here, we describe refined methods, new reagents, and how to implement their use for such screens.

Video: A Yeast 2-Hybrid Screen in Batch to Compare Protein Interactions

Fluorescence Anisotropy as a Tool to Study Protein-protein Interactions

Protein-protein interactions play an essential role in the function of a living organism. Once an interaction has been identified and validated it is necessary to characterize it at the structural and mechanistic level. Several biochemical and biophysical methods exist for such purpose. Among them, fluorescence anisotropy is a powerful technique particularly used when the fluorescence intensity of a fluorophore-labeled protein remains constant upon protein-protein interaction. In this technique, a fluorophore-labeled protein is excited with vertically polarized light of an appropriate wavelength that selectively excites a subset of the fluorophores according to their relative orientation with the incoming beam. The resulting emission also has a directionality whose relationship in the vertical and horizontal planes defines anisotropy (r) as follows: r=(IVV-IVH)/(IVV+2IVH), where IVV and IVH are the fluorescence intensities of the vertical and horizontal components, respectively. Fluorescence anisotropy is sensitive to the rotational diffusion of a fluorophore, namely the apparent molecular size of a fluorophore attached to a protein, which is altered upon protein-protein interaction. In the present text, the use of fluorescence anisotropy as a tool to study protein-protein interactions was exemplified to address the binding between the protein mutated in the Shwachman-Diamond Syndrome (SBDS) and the Elongation factor like-1 GTPase (EFL1). Conventionally, labeling of a protein with a fluorophore is carried out on the thiol groups (cysteine) or in the amino groups (the N-terminal amine or lysine) of the protein. However, SBDS possesses several cysteines and lysines that did not allow site directed labeling of it. As an alternative technique, the dye 4&#39;,5&#39;-bis(1,3,2 dithioarsolan-2-yl) fluorescein was used to specifically label a tetracysteine motif, Cys-Cys-Pro-Gly-Cys-Cys, genetically engineered in the C-terminus of the recombinant SBDS protein. Fitting of the experimental data provided quantitative and mechanistic information on the binding mode between these proteins.

Protein interactions are at the heart of a cell&#39;s function. Calorimetric and spectroscopic techniques are commonly used to characterize them. Here we describe fluorescence anisotropy as a tool to study the interaction between the protein mutated in the Shwachman-Diamond Syndrome (SBDS) and the Elongation factor-like 1 GTPase (EFL1).

Protein-protein interactions play an essential role in the function of a living organism. Once an interaction has been identified and validated it is ...

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

Studies of integral membrane proteins in vitro are frequently complicated by the presence of a hydrophobic transmembrane domain. Further complicating these studies, reincorporation of detergent-solubilized membrane proteins into liposomes is a stochastic process where protein topology is impossible to enforce. This paper offers an alternative method to these challenging techniques that utilizes a liposome-based scaffold. Protein solubility is enhanced by deletion of the transmembrane domain, and these amino acids are replaced with a tethering moiety, such as a His-tag. This tether interacts with an anchoring group (Ni2+ coordinated by nitrilotriacetic acid (NTA(Ni2+)) for His-tagged proteins), which enforces a uniform protein topology at the surface of the liposome. An example is presented wherein the interaction between Dynamin-related protein 1 (Drp1) with an integral membrane protein, Mitochondrial Fission Factor (Mff), was investigated using this scaffold liposome method. In this work, we have demonstrated the ability of Mff to efficiently recruit soluble Drp1 to the surface of liposomes, which stimulated its GTPase activity. Moreover, Drp1 was able to tubulate the Mff-decorated lipid template in the presence of specific lipids. This example demonstrates the effectiveness of scaffold liposomes using structural and functional assays and highlights the role of Mff in regulating Drp1 activity.

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

This paper describes a method for assessing the interactions and assemblies of integral membrane proteins in vitro with various partner factors in a lipid-proximal environment.

Studies of integral membrane proteins in vitro are frequently complicated by the presence of a hydrophobic transmembrane domain. Further complicating ...

Time-resolved ElectroSpray Ionization Hydrogen-deuterium Exchange Mass Spectrometry for Studying Protein Structure and Dynamics

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. Hydrogen-Deuterium Exchange (HDX) measured at rapid time scales is uniquely suited to detect structures and hydrogen bonding networks that are briefly populated, allowing for the characterization of transient conformers in native ensembles. Coupling of HDX to mass spectrometry offers several key advantages, including high sensitivity, low sample consumption and no restriction on protein size. This technique has advanced greatly in the last several decades, including the ability to monitor HDX labeling times on the millisecond time scale. In addition, by incorporating the HDX workflow onto a microfluidic platform housing an acidic protease microreactor, we are able to localize dynamic properties at the peptide level. In this study, Time-Resolved ElectroSpray Ionization Mass Spectrometry (TRESI-MS) coupled to HDX was used to provide a detailed picture of residual structure in the tau protein, as well as the conformational shifts induced upon hyperphosphorylation.

Conformational flexibility plays a critical role in protein function. Herein, we describe the use of time-resolved electrospray ionization mass spectrometry coupled to hydrogen-deuterium exchange for probing the rapid structural changes that drive function in ordered and disordered proteins.

Intrinsically disordered proteins (IDPs) have long been a challenge to structural biologists due to their lack of stable secondary structure elements. ...

A Modified Yeast-one Hybrid System for Heteromeric Protein Complex-DNA Interaction Studies

Over the years, the yeast one-hybrid assay has proven to be an important technique for the identification and validation of physical interactions between proteins such as transcription factors (TFs) and their DNA target. The method presented here utilizes the underlying concept of the Y1H but is modified further to study and validate protein complexes binding to their target DNA. Hence, it is referred to as the modified yeast one-hybrid (Y1.5H) assay. This assay is cost effective and can be easily performed in a regular laboratory setting. Albeit using a heterologous system, the described method could be a valuable tool to test and validate the heteromeric protein complex binding to their DNA target(s) for functional genomics in any system of study, especially plant genomics.

The modified yeast one-hybrid assay described here is an extension of the classical yeast one-hybrid (Y1H) assay to study and validate the heteromeric protein complex-DNA interaction in a heterologous system for any functional genomics study.

Over the years, the yeast one-hybrid assay has proven to be an important technique for the identification and validation of physical interactions between ...

Biotinylated Cell-penetrating Peptides to Study Intracellular Protein-protein Interactions

Here we present a protocol to study intracellular protein-protein interactions that is based on the widely used biotin-avidin pull-down system. The modification presented includes the combination of this technique with cell-penetrating sequences. We propose to design cell-penetrating baits that can be incubated with living cells instead of cell lysates and therefore the interactions found will reflect those that occur within the intracellular context. Connexin43 (Cx43), a protein that forms gap junction channels and hemichannels is down-regulated in high-grade gliomas. The Cx43 region comprising amino acids 266-283 is responsible for the inhibition of the oncogenic activity of c-Src in glioma cells. Here we use TAT as the cell-penetrating sequence, biotin as the pull-down tag and the region of Cx43 comprised between amino acids 266-283 as the target to find intracellular interactions in the hard-to-transfect human glioma stem cells. One of the limitations of the proposed method is that the molecule used as bait could fail to fold properly and, consequently, the interactions found could not be associated with the effect. However, this method can be especially interesting for the interactions involved in signal transduction pathways because they are usually carried out by intrinsically disordered regions and, therefore, they do not require an ordered folding. In addition, one of the advantages of the proposed method is that the relevance of each residue on the interaction can be easily studied. This is a modular system; therefore, other cell-penetrating sequences, other tags, and other intracellular targets can be employed. Finally, the scope of this protocol is far beyond protein-protein interaction because this system can be applied to other bioactive cargoes such as RNA sequences, nanoparticles, viruses or any molecule that can be transduced with cell-penetrating sequences and fused to pull-down tags to study their intracellular mechanism of action.

This is a protocol to study intracellular protein-protein interactions based on the biotin-avidin pull-down system with the novelty of combining cell-penetrating sequences. The main advantage is that the target sequence is incubated with living cells instead of cell lysates and therefore the interactions will occur within the cellular context.

Here we present a protocol to study intracellular protein-protein interactions that is based on the widely used biotin-avidin pull-down system. The ...

A Fluorescence Fluctuation Spectroscopy Assay of Protein-Protein Interactions at Cell-Cell Contacts

A variety of biological processes involves cell-cell interactions, typically mediated by proteins that interact at the interface between neighboring cells. Of interest, only few assays are capable of specifically probing such interactions directly in living cells. Here, we present an assay to measure the binding of proteins expressed at the surfaces of neighboring cells, at cell-cell contacts. This assay consists of two steps: mixing of cells expressing the proteins of interest fused to different fluorescent proteins, followed by fluorescence fluctuation spectroscopy measurements at cell-cell contacts using a confocal laser scanning microscope. We demonstrate the feasibility of this assay in a biologically relevant context by measuring the interactions of the amyloid precursor-like protein 1 (APLP1) across cell-cell junctions. We provide detailed protocols on the data acquisition using fluorescence-based techniques (scanning fluorescence cross-correlation spectroscopy, cross-correlation number and brightness analysis) and the required instrument calibrations. Further, we discuss critical steps in the data analysis and how to identify and correct external, spurious signal variations, such as those due to photobleaching or cell movement.
In general, the presented assay is applicable to any homo- or heterotypic protein-protein interaction at cell-cell contacts, between cells of the same or different types and can be implemented on a commercial confocal laser scanning microscope. An important requirement is the stability of the system, which needs to be sufficient to probe diffusive dynamics of the proteins of interest over several minutes.

This protocol describes a fluorescence fluctuation spectroscopy-based approach to investigate interactions among proteins mediating cell-cell interactions, i.e. proteins localized in cell junctions, directly in living cells. We provide detailed guidelines on instrument calibration, data acquisition and analysis, including corrections to possible artefact sources.

A variety of biological processes involves cell-cell interactions, typically mediated by proteins that interact at the interface between neighboring ...

A Fluorogenic Peptide Cleavage Assay to Screen for Proteolytic Activity: Applications for coronavirus spike protein activation

Enveloped viruses such as coronaviruses or influenza virus require proteolytic cleavage of their fusion protein to be able to infect the host cell. Often viruses exhibit cell and tissue tropism and are adapted to specific cell or tissue proteases. Moreover, these viruses can introduce mutations or insertions into their genome during replication that may affect the cleavage, and thus can contribute to adaptations to a new host. Here, we present a fluorogenic peptide cleavage assay that allows a rapid screening of peptides mimicking the cleavage site of viral fusion proteins. The technique is very flexible and can be used to investigate the proteolytic activity of a single protease on many different substrates, and in addition, it also allows exploration of the activity of multiple proteases on one or more peptide substrates. In this study, we used peptides mimicking the cleavage site motifs of the coronavirus spike protein. We tested human and camel derived Middle East Respiratory Syndrome coronaviruses (MERS-CoV) to demonstrate that single and double substitutions in the cleavage site can alter the activity of furin and dramatically change cleavage efficiency. We also used this method in combination with bioinformatics to test furin cleavage activity of feline coronavirus spike proteins from different serotypes and strains. This peptide-based method is less labor- and time intensive than conventional methods used for the analysis of proteolytic activity for viruses, and results can be obtained within a single day.

We present a fluorogenic peptide cleavage assay that allows a rapid screening of the proteolytic activity of proteases on peptides representing the cleavage site of viral fusion peptides. This method can also be used on any other amino acid motif within a protein sequence to test for the protease activity.

Enveloped viruses such as coronaviruses or influenza virus require proteolytic cleavage of their fusion protein to be able to infect the host cell. Often ...

Analysis of Protein Folding, Transport, and Degradation in Living Cells by Radioactive Pulse Chase

Radioactive pulse-chase labeling is a powerful tool for studying the conformational maturation, the transport to their functional cellular location, and the degradation of target proteins in live cells. By using short (pulse) radiolabeling times (&lt;30 min) and tightly controlled chase times, it is possible to label only a small fraction of the total protein pool and follow its folding. When combined with nonreducing/reducing SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoprecipitation with (conformation-specific) antibodies, folding processes can be examined in great detail. This system has been used to analyze the folding of proteins with a huge variation in properties such as soluble proteins, single and multi-pass transmembrane proteins, heavily N- and O-glycosylated proteins, and proteins with and without extensive disulfide bonding. Pulse-chase methods are the basis of kinetic studies into a range of additional features, including co- and posttranslational modifications, oligomerization, and polymerization, essentially allowing the analysis of a protein from birth to death. Pulse-chase studies on protein folding are complementary with other biochemical and biophysical methods for studying proteins in vitro by providing increased temporal resolution and physiological information. The methods as described within this paper are adapted easily to study the folding of almost any protein that can be expressed in mammalian or insect-cell systems.

Here we describe a protocol for a general pulse-chase method that allows the kinetic analysis of folding, transport, and degradation of proteins to be followed in live cells.

Radioactive pulse-chase labeling is a powerful tool for studying the conformational maturation, the transport to their functional cellular location, and ...

Application of Biolayer Interferometry (BLI) for Studying Protein-Protein Interactions in Transcription

A transcription factor&#160;(TF) is a protein that regulates gene expression by interacting with the RNA polymerase, another TF, and/or template DNA. GrgA is a novel transcription activator found specifically in the obligate intracellular bacterial pathogen Chlamydia. Protein pulldown assays using affinity beads have revealed that GrgA binds two &#963; factors, namely &#963;66 and &#963;28, which recognize different sets of promoters for genes whose products are differentially required at developmental stages. We have used BLI to confirm and further characterize the interactions. BLI demonstrates several advantages over pulldown: 1) It reveals real-time association and dissociation between binding partners, 2) It generates quantitative kinetic parameters, and 3) It can detect bindings that pulldown assays often fail to detect. These characteristics have enabled us to deduce the physiological roles of GrgA in gene expression regulation in Chlamydia, and possible detailed interaction mechanisms. We envision that this relatively affordable technology can be extremely useful for studying transcription and other biological processes.

Application of Biolayer Interferometry BLI for Studying Protein-Protein Interactions in Transcription

Interactions of transcription factors (TFs) with the RNA polymerase are usually studied using pulldown assays. We apply a Biolayer Interferometry (BLI) technology to characterize the interaction of GrgA with the chlamydial RNA polymerase. Compared to pulldown assays, BLI detects real-time association and dissociation, offers higher sensitivity, and is highly quantitative.

A transcription factor&#160;(TF) is a protein that regulates gene expression by interacting with the RNA polymerase, another TF, and/or template DNA. GrgA ...

Use of Microscale Thermophoresis to Measure Protein-Lipid Interactions

The ability to determine the binding affinity of lipids to proteins is an essential part of understanding protein-lipid interactions in membrane trafficking, signal transduction and cytoskeletal remodeling. Classic tools for measuring such interactions include surface plasmon resonance (SPR) and isothermal titration calorimetry (ITC). While powerful tools, these approaches have setbacks. ITC requires large amounts of purified protein as well as lipids, which can be costly and difficult to produce. Furthermore, ITC as well as SPR are very time consuming, which could add significantly to the cost of performing these experiments. One way to bypass these restrictions is to use the relatively new technique of microscale thermophoresis (MST). MST is fast and cost effective using small amounts of sample to obtain a saturation curve for a given binding event. There currently are two types of MST systems available. One type of MST requires labeling with a fluorophore in the blue or red spectrum. The second system relies on the intrinsic fluorescence of aromatic amino acids in the UV range. Both systems detect the movement of molecules in response to localized induction of heat from an infrared laser. Each approach has its advantages and disadvantages. Label-free MST can use untagged native proteins; however, many analytes, including pharmaceuticals, fluoresce in the UV range, which can interfere with determination of accurate KD values. In comparison, labeled MST allows for a greater diversity of measurable pairwise interactions utilizing fluorescently labeled probes attached to ligands with measurable absorbances in the visible range as opposed to UV, limiting the potential for interfering signals from analytes.

Microscale thermophoresis obtains binding constants quickly at low material cost. Either labeled or label free microscale thermophoresis is commercially available; however, label free thermophoresis is not capable of the diversity of interaction measurements that can be performed using fluorescent labels. We provide a protocol for labeled thermophoresis measurements.

A Yeast 2-Hybrid Screen in Batch to Compare Protein Interactions

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Chapters in this video

Fluorescence Anisotropy as a Tool to Study Protein-protein Interactions

Using Scaffold Liposomes to Reconstitute Lipid-proximal Protein-protein Interactions In Vitro

Time-resolved ElectroSpray Ionization Hydrogen-deuterium Exchange Mass Spectrometry for Studying Protein Structure and Dynamics

A Modified Yeast-one Hybrid System for Heteromeric Protein Complex-DNA Interaction Studies

Biotinylated Cell-penetrating Peptides to Study Intracellular Protein-protein Interactions

A Fluorescence Fluctuation Spectroscopy Assay of Protein-Protein Interactions at Cell-Cell Contacts

A Fluorogenic Peptide Cleavage Assay to Screen for Proteolytic Activity: Applications for coronavirus spike protein activation

Analysis of Protein Folding, Transport, and Degradation in Living Cells by Radioactive Pulse Chase

Application of Biolayer Interferometry (BLI) for Studying Protein-Protein Interactions in Transcription

Use of Microscale Thermophoresis to Measure Protein-Lipid Interactions