We thank Laura Vanderploeg for preparing figures. Work in the Sheets lab is supported by NSF grant 1050395 and NIH grant (R21HD076828). Work in the Ryder lab is supported by NIH grants R01GM117237 and R01GM117008. Megan Dowdle is supported by a SciMed GRS Advanced Opportunity Fellowship through University of Wisconsin-Madison Graduate School and Biotechnology Training Program through the National Institute of General Medical Sciences of the National Institutes of Health (T32GM008349).

1. Preparation of the Horizontal Native Polyacrylamide Gel4.
<ol>
	<li>Preparation of the materials needed.
	<ol>
		<li>For the horizontal gel apparatus, use a gel box (37 cm x 24 cm) with a 27 cm x 21 cm tray and a capacity for two 24-well combs. This setup provides a total of 48 samples that can be analyzed simultaneously.</li>
		<li>Prepare the following reagents: 40% Acrylamide-Bis 19:1, 5x TBE (Tris-Borate-EDTA pH 8.0), TEMED, and 10% APS (ammonium persulfate).</li>
	</ol>
	</li>
	<li>Generation of a 10% native acrylamide gel.
	<ol>
		<li>In a 500 mL flask, add 80 mL of 5x TBE, 100 mL of 40% acrylamide, and water to a final volume of 400 mL.</li>
		<li>Add 4 mL of 10% APS and 400 &#181;L of TEMED. Mix well.</li>
		<li>Pour the mix into the horizontal casting tray and allow the gel to polymerize for 30 min. The gel will be approximately 2 cm thick. 
		NOTE: Gels can cast in a fume hood to speed up polymerization. After polymerization, a thin layer of liquid will remain on top of the gel.</li>
		<li>Pour the liquid off and rinse with running buffer. Remove the comb(s) carefully and rinse the wells with running buffer using a syringe.</li>
	</ol>
	</li>
	<li>Preparation of running buffer.
	<ol>
		<li>Prepare 2 L of 1x TBE running buffer for the gel box. Dilute 400 mL of 5XTBE with 1600 mL and mix. Place 1x TBE buffer in cold room to cool.</li>
	</ol>
	</li>
	<li>Pre-Running the gel
	<ol>
		<li>Add 2 L of cold running buffer to the gel box and insert the gel.</li>
		<li>Pre-run the gel at 120 V for 1 h at 4 &#176;C in a cold room. During this time, prepare the binding reaction.</li>
	</ol>
	</li>
</ol>
2. Binding Reaction8
<ol>
	<li>2.1.Prepare the following reaction components. 
	20 mM DTT 
	10 mM BSA 
	10 mM yeast tRNAs 
	5X binding buffer (50 mM HEPES pH 8.0, 5 mM EDTA, 250 mM KCl, 0.2% Tween-20) 
	100 nM fluorescein labeled RNA purchased commercially 
	Concentrated Bicaudal-C protein 
	50% glycerol in DEPC-treated H2O 
	DEPC-treated H2O</li>
	<li>Assemble the binding reaction components in an RNase free microcentrifuge tube.
	<ol>
		<li>To the tube, add 5 &#181;L of 10 mM BSA, 5 &#181;L of 20 mM DTT, 5 &#181;L of 10 mM yeast tRNAs, 10 &#181;L of 5x Binding Buffer.</li>
	</ol>
	</li>
	<li>Add protein to a final concentration of 250 nM in 50 &#181;L. Add water to a final volume of 45 &#181;L.</li>
	<li>Add 5 &#181;L of fluorescently labeled RNA substrate. Use a commercially purchased 3&#39; fluorescein labeled 32-nucleotide substrate.</li>
	<li>Mix and incubate in the dark for 30 min at room temperature.</li>
</ol>
3. Analysis of Samples on the Native Horizontal Polyacrylamide Gel
<ol>
	<li>To each reaction, add 15 &#181;L of 50% glycerol and mix gently.</li>
	<li>Carefully add 30 &#181;L of each reaction to the gel. The amount of sample that can be loaded into a single well varies depending on the thickness of the gel and the size of the wells. We have loaded volumes as little as 15 &#181;L and as much as 45 &#181;L into a single well of gels created with a 24-well comb and poured to a thickness of 2 cm.</li>
	<li>After connecting the power supply to the gel apparatus switch on the power and adjust the voltage. Run the gel in 4 &#176;C at 120 V. 
	NOTE: For the horizontal gel apparatus, this ends up being approximately 5 V/cm. For the vertical gel apparatus, this is 16 V/cm.
	<ol>
		<li>To prevent damaging or bleaching of the fluorescently labeled RNA, conduct electrophoresis in the dark.</li>
		<li>Vary electrophoresis times depending upon the specifics of the RNA-protein complex being analyzed. 
		NOTE: A major advantage of the horizontal EMSA analysis is that electrophoresis can be stopped, the gel imaged and then the gel can be placed back into the apparatus and electrophoresis can be continued for longer times.</li>
	</ol>
	</li>
</ol>
4. Imaging the Gel
<ol>
	<li>Perform analysis with any instrument designed for detection and imaging fluorescent substrates.</li>
	<li>Place the gel on the imager.</li>
	<li>Adjust imager settings. For fluorescein-labeled RNA ligands, use the following settings: FAM (wavelength 473 nm), 750 Photomultiplier voltage (PMT), 100 &#181;m pixel size.</li>
	<li>Scan the gel to capture image.</li>
</ol>

<ol>
	<li>Ryder, S. P., Recht, M. I., Williamson, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+analysis+of+protein-RNA+interactions+by+gel+mobility+shift.">Quantitative analysis of protein-RNA interactions by gel mobility shift.</a> Methods Mol Biol. 488, 99-115 (2008).</li><li>Dahlberg, A. E., Dingman, C. W., Peacock, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophoretic+characterization+of+bacterial+polyribosomes+in+agarose-acrylamide+composite+gels.">Electrophoretic characterization of bacterial polyribosomes in agarose-acrylamide composite gels.</a> J Mol Biol. 41 (1), 139-147 (1969).</li><li>Hellman, L. M., Fried, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophoretic+mobility+shift+assay+(EMSA)+for+detecting+protein-nucleic+acid+interactions.">Electrophoretic mobility shift assay (EMSA) for detecting protein-nucleic acid interactions.</a> Nat Protoc. 2 (8), 1849-1861 (2007).</li><li>Pagano, J. M., Farley, B. M., Essien, K. I., Ryder, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+recognition+by+the+embryonic+cell+fate+determinant+and+germline+totipotency+factor+MEX-3.">RNA recognition by the embryonic cell fate determinant and germline totipotency factor MEX-3.</a> Proc Natl Acad Sci USA. 106 (48), 20252-20257 (2009).</li><li>Royer, C. A., Scarlata, S. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescence+approaches+to+quantifying+biomolecular+interactions.">Fluorescence approaches to quantifying biomolecular interactions.</a> Meth Enzymol. 450, 79-106 (2008).</li><li>Su, C., Wang, F., Ciolek, D., Pan, Y. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophoresis+of+proteins+and+protein-protein+complexes+in+native+polyacrylamide+gels+using+a+horizontal+gel+apparatus.">Electrophoresis of proteins and protein-protein complexes in native polyacrylamide gels using a horizontal gel apparatus.</a> Anal Biochem. 223, 93-98 (1994).</li><li>Buczek, P., Horvath, M. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermodynamic+Characterization+of+Binding+Oxytricha+nova+Single+Strand+Telomere+DNA+with+the+Alpha+Protein+N-terminal+Domain.">Thermodynamic Characterization of Binding Oxytricha nova Single Strand Telomere DNA with the Alpha Protein N-terminal Domain.</a> J Mol Biol. 359 (5), 1217-1234 (2006).</li><li>Zhang, Y., Park, S., Blaser, S., Sheets, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Determinants+of+RNA+binding+and+translational+repression+by+the+Bicaudal-C+regulatory+protein.">Determinants of RNA binding and translational repression by the Bicaudal-C regulatory protein.</a> J Biol Chem. 289 (11), 7497-7504 (2014).</li><li>Gamberi, C., Lasko, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Bic-C+family+of+developmental+translational+regulators.">The Bic-C family of developmental translational regulators.</a> Comp Funct Genomics. , 141386 (2012).</li><li>Saffman, E. E., 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=Premature+translation+of+oskar+in+oocytes+lacking+the+RNA-binding+protein+bicaudal-C.">Premature translation of oskar in oocytes lacking the RNA-binding protein bicaudal-C.</a> Mol Cell Biol. 18 (8), 4855-4862 (1998).</li><li>Chicoine, J., 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=Bicaudal-C+recruits+CCR4-NOT+deadenylase+to+target+mRNAs+and+regulates+oogenesis,+cytoskeletal+organization,+and+its+own+expression.">Bicaudal-C recruits CCR4-NOT deadenylase to target mRNAs and regulates oogenesis, cytoskeletal organization, and its own expression.</a> Dev Cell. 13 (5), 691-704 (2007).</li><li>Zhang, Y., 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=Bicaudal-C+spatially+controls+translation+of+vertebrate+maternal+mRNAs.">Bicaudal-C spatially controls translation of vertebrate maternal mRNAs.</a> RNA. 19 (11), 1575-1582 (2013).</li><li>Maisonneuve, C., 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=Bicaudal+C,+a+novel+regulator+of+Dvl+signaling+abutting+RNA-processing+bodies,+controls+cilia+orientation+and+leftward+flow.">Bicaudal C, a novel regulator of Dvl signaling abutting RNA-processing bodies, controls cilia orientation and leftward flow.</a> Development. 136 (17), 3019-3030 (2009).</li><li>Tran, U., 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=The+RNA-binding+protein+bicaudal+C+regulates+polycystin+2+in+the+kidney+by+antagonizing+miR-17+activity.">The RNA-binding protein bicaudal C regulates polycystin 2 in the kidney by antagonizing miR-17 activity.</a> Development. 137 (7), 1107-1116 (2010).</li><li>Pagano, J. M., Clingman, C. C., Ryder, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitative+approaches+to+monitor+protein-nucleic+acid+interactions+using+fluorescent+probes.">Quantitative approaches to monitor protein-nucleic acid interactions using fluorescent probes.</a> RNA. 17 (1), 14-20 (2011).</li><li>Foley, T. L., 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=Platform+to+Enable+the+Pharmacological+Profiling+of+Small+Molecules+in+Gel-Based+Electrophoretic+Mobility+Shift+Assays.">Platform to Enable the Pharmacological Profiling of Small Molecules in Gel-Based Electrophoretic Mobility Shift Assays.</a> J Biomol Screen. 21 (10), 1125-1131 (2016).</li></ol>

The authors have nothing to disclose.

Native polyacrylamide gels are an invaluable tool for investigating protein-RNA interactions and traditionally these gels are electrophoresed vertically2,3. We have used a modification of the protocol that substitutes native polyacrylamide gels created and electrophoresed horizontally1,4,6,7,15. These ...

Electrophoretic mobility shift assays (EMSAs) have proven to be an invaluable biochemical tool to analyze specific protein-nucleic acid interactions1,2,3. These assays can provide important information regarding the binding affinity of proteins to RNA or DNA3, the component stoichiometry of nucleic acid-protein complexes1 and provide important new insights about the binding specificity of RNA binding proteins via substrate competition experiments1.
The traditional experimental setup for these assays consists of mixing purified protein with a radiolabeled RNA substrate. The resulting complexes are then analyzed with non-denaturing (native) polyacrylamide gels poured between two glass plates followed by sample electrophoresis in a vertical apparatus3. While this approach has been used exhaustively to provide important insights in the biochemical mechanisms that underlie the binding of proteins to nucleic acids, it also has several limitations. For example, this basic strategy has relatively low throughput and it is not readily adaptable for applications that require analyzing many binding reactions in parallel. In addition, with the traditional vertical apparatus it is challenging to potentially monitor complexes at multiple times during electrophoresis3,4.
Here we present an adaptation of the EMSA assay that uses native polyacrylamide gels cast in a flatbed apparatus, horizontal electrophoresis and fluorescently labeled RNA substrates4,5,6,7. The incorporation of these relatively simple modifications to the basic strategy provides some powerful advantages. In particular, the horizontal flatbed format easily lends itself to analyzing dozens of samples simultaneously4. Also, for some RNA-protein complexes, such as those formed between the Bicaudal-C protein and its RNA substrate electrophoresis in a horizontal gel provides an increased ability to resolve distinct RNA-protein complexes and discriminate these from unbound RNA substrate.

<table><tbody><tr><td>Horizontal Gel Box</td><td>OWL</td><td>N/A</td><td>Product no longer made. Similar gel boxes can be found at Thermo Scientific, A-series gel boxes. Catalog Number: A2-BP</td></tr><tr><td>24-well large large horizontal gel electrophoresis combs</td><td>OWL</td><td>N/A</td><td>Product no longer made. Similar gel boxes can be found at Thermo Scientific, A-series gel box combs. Catalog Number: A2-24C</td></tr><tr><td>Powerpac 300</td><td>Bio-Rad</td><td>1655050</td><td></td></tr><tr><td>Mini-Protean II Electrophoresis Cell</td><td>Bio-Rad</td><td>165-2940</td><td></td></tr><tr><td>InstaPAGE-19 40% 19:1 Acrylamide/Bis</td><td>IBI</td><td>IB70015</td><td></td></tr><tr><td>TEMED</td><td>IBI</td><td>IB70120</td><td></td></tr><tr><td>APS</td><td>IBI</td><td>IB70080</td><td></td></tr><tr><td>Yeast tRNAs</td><td>Ambion</td><td>AM7119</td><td></td></tr><tr><td>Fluorescein labeled RNA</td><td>IDT</td><td>N/A</td><td>Order can be made custom to length and desired sequence</td></tr><tr><td>EDTA tetrasodium salt hydrate</td><td>Sigma-Aldrich</td><td>E5391-1KG</td><td></td></tr><tr><td>HEPES</td><td>Sigma-Aldrich</td><td>H4034-500G</td><td></td></tr><tr><td>Tris Base Ultrapure</td><td>US Biological</td><td>T8600</td><td></td></tr><tr><td>Boric Acid</td><td>Fisher Scientific</td><td>BP168-500</td><td></td></tr><tr><td>Potassium Chloride</td><td>Fisher Scientific</td><td>BP366-1</td><td></td></tr><tr><td>Tween-20</td><td>Fisher Scientific</td><td>BP337-500</td><td></td></tr><tr><td>DEPC</td><td>Sigma-Aldrich</td><td>1609-47-8</td><td></td></tr><tr><td>Dithiothreitol (DTT)</td><td>Sigma-Aldrich</td><td>3483 12 3</td><td></td></tr><tr><td>Bovine Serum Albumin (BSA)</td><td>Sigma-Aldrich</td><td>9048-46-8</td><td></td></tr></tbody></table>

horizontal gel electrophoresis for enhanced detection of protein-rna complexes

Native polyacrylamide gel electrophoresis is a fundamental tool of molecular biology that has been used extensively for the biochemical analysis of RNA-protein interactions. These interactions have been traditionally analyzed with polyacrylamide gels generated between two glass plates and samples electrophoresed vertically. However, polyacrylamide gels cast in trays and electrophoresed horizontally offers several advantages. For example, horizontal gels used to analyze complexes between fluorescent RNA substrates and specific proteins can be imaged multiple times as electrophoresis progresses. This provides the unique opportunity to monitor RNA-protein complexes at several points during the experiment. In addition, horizontal gel electrophoresis makes it possible to analyze many samples in parallel. This can greatly facilitate time course experiments as well as analyzing multiple reactions simultaneously to compare different components and conditions. Here we provide a detailed protocol for generating and using horizontal native gel electrophoresis for analyzing RNA-Protein interactions.

To demonstrate the power and versatility of the horizontal native gel electrophoresis we analyzed the binding of the Xenopus Bicaudal-C (Bicc1) protein to a fluorescently labeled RNA containing a Bicc1 binding site. Bicc1 proteins function as mRNA-specific translational repressors to control cell fate decisions during the maternal stages of animal development9,10,11,<sup class...

Watch this Scientific Journal Video about Horizontal Gel Electrophoresis for Enhanced Detection of Protein-RNA Complexes at JoVE.com

Horizontal Gel Electrophoresis for Enhanced Detection of Protein-RNA Complexes

Native polyacrylamide gel electrophoresis is a fundamental tool for analyzing RNA-protein interactions. Traditionally most experiments have used vertical gels. However, horizontal gels provide several advantages, such as the opportunity to monitor complexes during electrophoresis. We provide a detailed protocol for generating and using horizontal native gel electrophoresis.

Native polyacrylamide gel electrophoresis is a fundamental tool of molecular biology that has been used extensively for the biochemical analysis of ...

horizontal-gel-electrophoresis-for-enhanced-detection-protein-rna

Research

JoVE Journal

Biochemistry

11.9K Views.  University of Wisconsin School of Medicine and Public Health.  Inheemse polyacrylamide gelelektroforese is een fundamenteel hulpmiddel voor het analyseren van RNA-eiwitinteracties. Traditioneel hebben de meeste experimenten verticale gels gebruikt. Horizontale gels verschaffen echter verschillende voordelen, zoals de mogelijkheid om complexen te monitoren tijdens elektroforese. Wij bieden een gedetailleerd protocol voor het genereren en gebruiken van horizontale inheemse gelelektroforese. 

Video: Horizontal Gel Electrophoresis for Enhanced Detection of Protein-RNA Complexes

Novel RNA-Binding Proteins Isolation by the RaPID Methodology

RNA-binding proteins (RBPs) play important roles in every aspect of RNA metabolism and regulation. Their identification is a major challenge in modern biology. Only a few in vitro and in vivo methods enable the identification of RBPs associated with a particular target mRNA. However, their main limitations are the identification of RBPs in a non-cellular environment (in vitro) or the low efficiency isolation of RNA of interest (in vivo). An RNA-binding protein purification and identification (RaPID) methodology was designed to overcome these limitations in yeast and enable efficient isolation of proteins that are associated in vivo. To achieve this, the RNA of interest is tagged with MS2 loops, and co-expressed with a fusion protein of an MS2-binding protein and a streptavidin-binding protein (SBP). Cells are then subjected to crosslinking and lysed, and complexes are isolated through streptavidin beads. The proteins that co-purify with the tagged RNA can then be determined by mass spectrometry. We recently used this protocol to identify novel proteins associated with the ER-associated PMP1 mRNA. Here, we provide a detailed protocol of RaPID, and discuss some of its limitations and advantages.

RNA-protein interactions lie at the heart of many cellular processes. Here, we describe an in vivo method to isolate specific RNA and identify novel proteins that are associated with it. This could shed new light on how RNAs are regulated in the cell.

RNA-binding proteins (RBPs) play important roles in every aspect of RNA metabolism and regulation. Their identification is a major challenge in modern ...

Genetics

An Optimized Protocol for Electrophoretic Mobility Shift Assay Using Infrared Fluorescent Dye-labeled Oligonucleotides

Electrophoretic Mobility Shift Assays (EMSA) are an instrumental tool to characterize the interactions between proteins and their target DNA sequences. Radioactivity has been the predominant method of DNA labeling in EMSAs. However, recent advances in fluorescent dyes and scanning methods have prompted the use of fluorescent tagging of DNA as an alternative to radioactivity for the advantages of easy handling, saving time, reducing cost, and improving safety. We have recently used fluorescent EMSA (fEMSA) to successfully address an important biological question. Our fEMSA analysis provides mechanistic insight into the effect of a missense mutation, G73E, in the highly conserved HMG transcription factor SOX-2 on olfactory neuron type diversification. We found that mutant SOX-2G73E protein alters specific DNA binding activity, thereby causing olfactory neuron identity transformation. Here, we present an optimized and cost-effective step-by-step protocol for fEMSA using infrared fluorescent dye-labeled oligonucleotides containing the LIM-4/SOX-2 adjacent target sites and purified SOX-2 proteins (WT and mutant SOX-2G73E proteins) as a biological example.

We describe here an optimized protocol of fluorescent Electrophoretic Mobility Shift Assays (fEMSA) using purified SOX-2 proteins together with infrared fluorescent dye-labeled DNA probes as a case study to tackle an important biological question.

Electrophoretic Mobility Shift Assays (EMSA) are an instrumental tool to characterize the interactions between proteins and their target DNA sequences. ...

Protein-tRNA Agarose Gel Retardation Assays for the Analysis of the N6-threonylcarbamoyladenosine TcdA Function

We demonstrate methods for the expression and purification of tRNA(UUU) in Escherichia coli and the analysis by gel retardation assays of the binding of tRNA(UUU) to TcdA, an N6-threonylcarbamoyladenosine (t6A) dehydratase, which cyclizes the threonylcarbamoyl side chain attached to A37 in the anticodon stem loop (ASL) of tRNAs to cyclic t6A (ct6A). Transcription of the synthetic gene encoding tRNA(UUU) is induced in E. coli with 1 mM isopropyl &#946;-D-1-thiogalactopyranoside (IPTG) and the cells containing tRNA are harvested 24 h post-induction. The RNA fraction is purified using the acid phenol extraction method. Pure tRNA is obtained by a gel filtration chromatography that efficiently separates the small-sized tRNA molecules from larger intact or fragmented nucleic acids. To analyze TcdA binding to tRNA(UUU), TcdA is mixed with tRNA(UUU) and separated on a native agarose gel at 4 &#176;C. The free tRNA(UUU) migrates faster, while the TcdA-tRNA(UUU) complexes undergo a mobility retardation that can be observed upon staining of the gel. We demonstrate that TcdA is a tRNA(UUU)-binding enzyme. This gel retardation assay can be used to study TcdA mutants and the effects of additives and other proteins on binding.

Protein-tRNA Agarose Gel Retardation Assays for the Analysis of the N6-threonylcarbamoyladenosine TcdA Function

A protocol is presented for the production of tRNA(UUU) and the analysis of tRNA(UUU) in complex with the enzyme TcdA by agarose gel retardation assays.

We demonstrate methods for the expression and purification of tRNA(UUU) in Escherichia coli and the analysis by gel retardation assays of the binding of ...

Sequence-specific and Selective Recognition of Double-stranded RNAs over Single-stranded RNAs by Chemically Modified Peptide Nucleic Acids

RNAs are emerging as important biomarkers and therapeutic targets. Thus, there is great potential in developing chemical probes and therapeutic ligands for the recognition of RNA sequence and structure. Chemically modified Peptide Nucleic Acid (PNA) oligomers have been recently developed that can recognize RNA duplexes in a sequence-specific manner. PNAs are chemically stable with a neutral peptide-like backbone. PNAs can be synthesized relatively easily by the manual Boc-chemistry solid-phase peptide synthesis method. PNAs are purified by reverse-phase HPLC, followed by molecular weight characterization by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF). Non-denaturing polyacrylamide gel electrophoresis (PAGE) technique facilitates the imaging of the triplex formation, because carefully designed free RNA duplex constructs and PNA bound triplexes often show different migration rates. Non-denaturing PAGE with ethidium bromide post staining is often an easy and informative technique for characterizing the binding affinities and specificities of PNA oligomers. Typically, multiple RNA hairpins or duplexes with single base pair mutations can be used to characterize PNA binding properties, such as binding affinities and specificities. 2-Aminopurine is an isomer of adenine (6-aminopurine); the 2-aminopurine fluorescence intensity is sensitive to local structural environment changes, and is suitable for the monitoring of triplex formation with the 2-aminopurine residue incorporated near the PNA binding site. 2-Aminopurine fluorescence titration can also be used to confirm the binding selectivity of modified PNAs towards targeted double-stranded RNAs (dsRNAs) over single-stranded RNAs (ssRNAs). UV-absorbance-detected thermal melting experiments allow the measurement of the thermal stability of PNA-RNA duplexes and PNA&#183;RNA2 triplexes. Here, we describe the synthesis and purification of PNA oligomers incorporating modified residues, and describe biochemical and biophysical methods for characterization of the recognition of RNA duplexes by the modified PNAs.

We report the protocols for the synthesis and purification of Peptide Nucleic Acid (PNA) oligomers incorporating modified residues. The biochemical and biophysical methods for the characterization of the recognition of RNA duplexes by the modified PNAs are described.

RNAs are emerging as important biomarkers and therapeutic targets. Thus, there is great potential in developing chemical probes and therapeutic ligands ...

iCLIP - Transcriptome-wide Mapping of Protein-RNA Interactions with Individual Nucleotide Resolution

The unique composition and spatial arrangement of RNA-binding proteins (RBPs) on a transcript guide the diverse aspects of post-transcriptional regulation1. Therefore, an essential step towards understanding transcript regulation at the molecular level is to gain positional information on the binding sites of RBPs2.
Protein-RNA interactions can be studied using biochemical methods, but these approaches do not address RNA binding in its native cellular context. Initial attempts to study protein-RNA complexes in their cellular environment employed affinity purification or immunoprecipitation combined with differential display or microarray analysis (RIP-CHIP)3-5. These approaches were prone to identifying indirect or non-physiological interactions6. In order to increase the specificity and positional resolution, a strategy referred to as CLIP (UV cross-linking and immunoprecipitation) was introduced7,8. CLIP combines UV cross-linking of proteins and RNA molecules with rigorous purification schemes including denaturing polyacrylamide gel electrophoresis. In combination with high-throughput sequencing technologies, CLIP has proven as a powerful tool to study protein-RNA interactions on a genome-wide scale (referred to as HITS-CLIP or CLIP-seq)9,10. Recently, PAR-CLIP was introduced that uses photoreactive ribonucleoside analogs for cross-linking11,12.
Despite the high specificity of the obtained data, CLIP experiments often generate cDNA libraries of limited sequence complexity. This is partly due to the restricted amount of co-purified RNA and the two inefficient RNA ligation reactions required for library preparation. In addition, primer extension assays indicated that many cDNAs truncate prematurely at the crosslinked nucleotide13. Such truncated cDNAs are lost during the standard CLIP library preparation protocol. We recently developed iCLIP (individual-nucleotide resolution CLIP), which captures the truncated cDNAs by replacing one of the inefficient intermolecular RNA ligation steps with a more efficient intramolecular cDNA circularization (Figure 1)14. Importantly, sequencing the truncated cDNAs provides insights into the position of the cross-link site at nucleotide resolution. We successfully applied iCLIP to study hnRNP C particle organization on a genome-wide scale and assess its role in splicing regulation14.

The spatial arrangement of RNA-binding proteins on a transcript is a key determinant of post-transcriptional regulation. Therefore, we developed individual-nucleotide resolution UV crosslinking and immunoprecipitation (iCLIP) that allows precise genome-wide mapping of the binding sites of an RNA-binding protein.

The unique composition and spatial arrangement of RNA-binding proteins (RBPs) on a transcript guide the diverse aspects of post-transcriptional ...

Biology

Enhanced Northern Blot Detection of Small RNA Species in Drosophila Melanogaster

The last decades have witnessed the explosion of scientific interest around gene expression control mechanisms at the RNA level. This branch of molecular biology has been greatly fueled by the discovery of noncoding RNAs as major players in post-transcriptional regulation. Such a revolutionary perspective has been accompanied and triggered by the development of powerful technologies for profiling short RNAs expression, both at the high-throughput level (genome-wide identification) or as single-candidate analysis (steady state accumulation of specific species). Although several state-of-art strategies are currently available for dosing or visualizing such fleeing molecules, Northern Blot assay remains the eligible approach in molecular biology for immediate and accurate evaluation of RNA expression. It represents a first step toward the application of more sophisticated, costly technologies and, in many cases, remains a preferential method to easily gain insights into RNA biology. Here we overview an efficient protocol (Enhanced Northern Blot) for detecting weakly expressed microRNAs (or other small regulatory RNA species) from Drosophila melanogaster whole embryos, manually dissected larval/adult tissues or in vitro cultured cells. A very limited amount of RNA is required and the use of material from flow cytometry-isolated cells can be also envisaged.

Enhanced Northern Blot Detection of Small RNA Species in Drosophila Melanogaster

The aim of this publication is to visualize and discuss the operative steps of an Enhanced Northern Blot protocol on RNA extracted from Drosophila melanogaster embryos, cells, and tissues. This protocol is particularly useful for the efficient detection of small RNA species.

The last decades have witnessed the explosion of scientific interest around gene expression control mechanisms at the RNA level. This branch of molecular ...

Electrophoretic Mobility Shift Assay (EMSA) for the Study of RNA-Protein Interactions: The IRE/IRP Example

RNA/protein interactions are critical for post-transcriptional regulatory pathways. Among the best-characterized cytosolic RNA-binding proteins are iron regulatory proteins, IRP1 and IRP2. They bind to iron responsive elements (IREs) within the untranslated regions (UTRs) of several target mRNAs, thereby controlling the mRNAs translation or stability. IRE/IRP interactions have been widely studied by EMSA. Here, we describe the EMSA protocol for analyzing the IRE-binding activity of IRP1 and IRP2, which can be generalized to assess the activity of other RNA-binding proteins as well. A crude protein lysate containing an RNA-binding protein, or a purified preparation of this protein, is incubated with an excess of32 P-labeled RNA probe, allowing for complex formation. Heparin is added to preclude non-specific protein to probe binding. Subsequently, the mixture is analyzed by non-denaturing electrophoresis on a polyacrylamide gel. The free probe migrates fast, while the RNA/protein complex exhibits retarded mobility; hence, the procedure is also called &#8220;gel retardation&#8221; or &#8220;bandshift&#8221; assay. After completion of the electrophoresis, the gel is dried and RNA/protein complexes, as well as free probe, are detected by autoradiography. The overall goal of the protocol is to detect and quantify IRE/IRP and other RNA/protein interactions. Moreover, EMSA can also be used to determine specificity, binding affinity, and stoichiometry of the RNA/protein interaction under investigation.

Electrophoretic Mobility Shift Assay EMSA for the Study of RNA-Protein Interactions: The IRE/IRP Example

Here we present a protocol to analyze RNA/protein interactions. The electrophoretic mobility shift assay (EMSA) is based on the differential migration of RNA/protein complexes and free RNA during native gel electrophoresis. By using a radiolabeled RNA probe, RNA/protein complexes can be visualized by autoradiography.

RNA/protein interactions are critical for post-transcriptional regulatory pathways. Among the best-characterized cytosolic RNA-binding proteins are iron ...

Enhanced Crosslinking Immunoprecipitation (eCLIP) Method for Efficient Identification of Protein-bound RNA in Mouse Testis

Spermatogenesis defines a highly ordered process of male germ cell differentiation in mammals. In testis, transcription and translation are uncoupled, underlining the importance of post-transcriptional regulation of gene expression orchestrated by RBPs. To elucidate mechanistic roles of an RBP, crosslinking immunoprecipitation (CLIP) methodology can be used to capture its endogenous direct RNA targets and define the actual interaction sites. The enhanced CLIP (eCLIP) is a newly-developed method that offers several advantages over the conventional CLIPs. However, the use of eCLIP has so far been limited to cell lines, calling for expanded applications. Here, we employed eCLIP to study MOV10 and MOV10L1, two known RNA-binding helicases, in mouse testis. As expected, we find that MOV10 predominantly binds to 3' untranslated regions (UTRs) of mRNA and MOV10L1 selectively binds to Piwi-interacting RNA (piRNA) precursor transcripts. Our eCLIP method allows fast determination of major RNA species bound by various RBPs via small-scale sequencing of subclones and thus availability of qualified libraries, as a warrant for proceeding with deep sequencing. This study establishes an applicable basis for eCLIP in mammalian testis.

Enhanced Crosslinking Immunoprecipitation eCLIP Method for Efficient Identification of Protein-bound RNA in Mouse Testis

Here, we present an eCLIP protocol to determine major RNA targets of RBP candidates in testis.

Spermatogenesis defines a highly ordered process of male germ cell differentiation in mammals. In testis, transcription and translation are uncoupled, ...

Electrophoretic Mobility Shift Assay for Detection of Transcription Factor-DNA Complexes

Source: Hsieh, Y. W. et al., <a href="https://app.jove.com/v/54863">An Optimized Protocol for Electrophoretic Mobility Shift Assay Using Infrared Fluorescent Dye-labeled Oligonucleotides.</a> J. Vis. Exp. (2016)
In this video, we demonstrate the electrophoretic mobility shift assay to detect protein-DNA interactions using infrared fluorescent-labeled DNA probes. When the protein binds to the DNA probe, it forms a large complex that migrates slowly on and appears as a shifted band on the gel.

Source: Hsieh, Y. W. et al., An Optimized Protocol for Electrophoretic Mobility Shift Assay Using Infrared Fluorescent Dye-labeled Oligonucleotides. J. ...

JoVE Encyclopedia of Experiments

Biological Techniques

Biomolecular Interaction Detection Techniques

Protein-nucleic acid interactions

Denaturing Urea Polyacrylamide Gel Electrophoresis for RNA Analysis: A Technique to Separate Fluorescently Labeled Phosphorylated RNA Oligonucleotides from their Non-Phosphorylated Equivalents

Source: Pillon, M. C., et al., <a href="https://www.jove.com/v/61258">Nonradioactive Assay to Measure Polynucleotide Phosphorylation of Small Nucleotide Substrates</a>. J. Vis. Exp. (2020)
In this video, we demonstrate a denaturing polyacrylamide gel electrophoresis for the separation of phosphorylated RNA species from their non-phosphorylated counterparts. The RNA species are fluorescently labeled for laser detection on the gel.

Source: Pillon, M. C., et al., Nonradioactive Assay to Measure Polynucleotide Phosphorylation of Small Nucleotide Substrates. J. Vis. Exp. (2020)
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Horizontal Gel Electrophoresis for Enhanced Detection of Protein-RNA Complexes

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