The authors acknowledge the access to radiation lab provided by the host institute and BRIT for radioisotope.&#160;PVS laboratory is supported by National Center for Biological Sciences, Tata Institute for Fundamental Research and grants (BT/PR12394/AGIII/103/891/2014; BT/IN/Swiss/47/JGK/2018-19; BT/PR25767/GET/119/151/2017) from Department of Biotechnology, Government of India. MP acknowledges DBT-Research Associateship, DBT, Government of India.

1. Preparation of a 15% denaturing polyacrylamide gel
<ol>
	<li>Weigh and add 4.8 g of urea, add 3.75 mL of 40% acrylamide: bisacrylamide (19:1) solution and 1 mL of 10x TBE pH 8.2 into a sterile 50 mL tube.</li>
	<li>Dissolve the urea using a water bath set at 60 &#176;C into a clear solution.</li>
	<li>Make-up the volume to 10 mL using freshly autoclaved sterile water and cool the gel mix to room temperature.</li>
	<li>Prepare fresh 10% (w/v) ammonium persulfate solution.</li>
</ol>
2. Assembly of the glass plates and electrophoresis unit
<ol>
	<li>Wash all the apparatus required for the gel electrophoresis and electro-blotting with detergent. Gently scrub them using a soft sponge to remove residual buffer and acrylamide, rinse with water and allow them to dry.</li>
	<li>Assemble both the glass plates together and place them firmly on the sponge. Use a 1 mm thick plate for this setup. Make sure that the plates are at the same level to avoid leakage.</li>
	<li>To the 10 mL gel mix, add 8 &#181;L of TEMED and 80 &#181;L of freshly prepared 10% (w/v) ammonium persulfate solution.</li>
	<li>Without delay, gently mix and pour this in between the assembled glass plates. Place the comb carefully. Avoid generating air-bubbles in this step.</li>
	<li>Allow the gel to polymerize for approximately 45 min.</li>
	<li>Wash the polymerized gel with sterile water before placing inside the gel-running setup.</li>
	<li>Assemble the plates inside the running cassette and remove the comb gently.</li>
	<li>Pour freshly prepared sterile 1x TBE, pH 8.2 into the tank.</li>
	<li>Wash the wells carefully by pipetting the buffer to remove salt crystals. This step helps the RNA sample to run uniformly across the gel.</li>
	<li>Perform a pre-run at 80 V for 30 min.</li>
</ol>
3. Preparation of loading dye and samples
<ol>
	<li>For 10 mL of gel loading dye, weigh 5 mg of bromophenol blue, 5 mg of xylene cyanol, add 10 mL of deionized formamide carefully and mix them well.</li>
	<li>Aliquot 10 &#181;g of total RNA into a sterile 1.5 mL tube and dry the samples using a speedvac. Do not over-dry the samples.</li>
	<li>Resuspend the RNA samples in 8 &#181;L of loading.</li>
	<li>Heat the samples at 98 &#176;C for 2 min, cool for 1 min at RT, vortex and spin the samples, for 3 times. This step is essential for proper resuspension and in turn this helps in equal loading of the samples.</li>
</ol>
4. Gel electrophoresis
<ol>
	<li>Stop the pre-run and wash the wells before sample loading.</li>
	<li>Heat the samples at 98 &#176;C for 1 min and load the samples hot into the well using capillary tips. Insert the tip to the bottom of the well, so that sample occupies one thin layer in the well.</li>
	<li>Complete loading of all the samples. Include to load RNA decade marker.</li>
	<li>Run the gel at 80 V until the bromophenol blue dye runs almost completely. Bromophenol blue runs at 10 bp in a 15% denaturing acrylamide gel.</li>
</ol>
5. Preparation for electro-blotting
<ol>
	<li>Cut the N+nylon membrane to the dimensions of glass plate and label the membrane at its top-right corner with a HB pencil.</li>
	<li>Gently place the membrane on surface of sterile water, facing the labeled side towards water surface. Pre-soak the membrane for 15 min.</li>
	<li>Cut 4 pieces of blotting paper I to the dimensions of fiber pad.</li>
	<li>Prepare the gel sandwich for placing the gray side of the cassette down in a clean tray.</li>
	<li>Pre-wet the fiber pad and place it over the cassette. Remove air bubbles.</li>
	<li>Pre-wet one piece of blotting paper in 1x TBE and place over the fiber pad. Remove air bubbles by rolling a plastic pipette over the paper. Lay another piece of pre-wet blotting paper and remove air bubbles.</li>
	<li>Carefully remove the gel from the running cassette and place it over the sandwich setup, such that the first loaded RNA sample is towards the right.</li>
	<li>Gently dip the pre-soaked membrane in 1x TBE and place it over the gel, facing the labelled side down. Roll out to remove the air bubbles.</li>
	<li>Dip a piece of blotting paper, lay it over the membrane, and remove the air bubbles. Dip another piece of blotting paper, place it over sandwich setup and remove air bubbles.</li>
	<li>Complete the sandwich by placing a pre-wet fiber pad over the setup and firmly close the cassette.</li>
	<li>Place the transblot cassette in the module and fill 1x TBE, pH 8.2 up to the blotting mark.</li>
	<li>Transfer at 10 V, overnight at 4 &#176;C.</li>
	<li>After transfer, place the damp membrane on a paper sheet and immediately cross-link the RNA to the membrane by irradiation with 254-nm UV light (120,000 &#181;joules/cm&#178;). The cross-linked blot maybe stored at 4 &#176;C for further hybridization.</li>
</ol>
6. Preparation of radiolabeled probe
<ol>
	<li>Design a probe that is completely complementary to the small RNA which is to be detected.</li>
	<li>End label the probe using &#435;P32ATP (obtained from BRIT) at its 5&#8217; end by combining the components as per recipe provided in Table 1.</li>
	<li>Incubate the above reaction mixture at 37 &#176;C for 30 min.</li>
	<li>Separate un-labelled &#435;P32ATP from probe by using a Sephadex G-25 column according to manufacturer&#8217;s protocol.</li>
</ol>
7. Hybridization of the blot
<ol>
	<li>Place the crossed-linked blot, RNA side facing top inside a hybridization bottle.</li>
	<li>Vigorously mix the ultra-sensitive hybridization buffer, add 10 mL of it and incubate the blot inside a hybridization oven maintained at 35 &#176;C, with rotation.</li>
	<li>Perform pre-hybridization for 20 min.</li>
	<li>Remove the bottle from the oven and add the labelled probe into the hybridization buffer gently.</li>
	<li>Hybridize the blot at 35 &#176;C, with rotation for 12 h.</li>
	<li>After hybridization carefully transfer the hybridization solution into 15 mL tube. This solution can be stored at 4 &#176;C until re-use.</li>
	<li>Perform a quick wash of the blot for 2 min to remove excess hybridization solution by adding 2x SSC buffer plus 0.5% SDS. Discard the solution.</li>
	<li>Incubate the blot with 2x SSC buffer plus 0.5% SDS for 35 &#176;C, with rotation for 30 min.</li>
	<li>Wash the blot again with 0.5x SSC buffer plus 0.5% SDS for 35&#176;C, with rotation for 30 min.</li>
	<li>Place the blot inside a hybridization cover, remove the excess buffer and seal it.</li>
	<li>Expose it to a radiation free-phosphor imager screen overnight inside a cassette.</li>
	<li>Detect the hybridization signal using biomolecular imager and analyze the results using suitable software.</li>
	<li>Strip the blot by incubating it at 80 &#176;C, with rotation for 30 min with 0.5 X SSC buffer plus 0.1% SDS and 0.1 X SSC buffer plus 0.1% SDS for 30 min.</li>
</ol>

<ol>
	<li>Baulcombe, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+silencing+in+plants.">RNA silencing in plants.</a> Nature. 431, 356-363 (2004).</li><li>Anushree, N., Shivaprasad, P. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+Plant+miRNA+Biogenesis.">Regulation of Plant miRNA Biogenesis.</a> Proceedings of the Indian National Science Academy. 95, (2017).</li><li>Narjala, A., Nair, A., Tirumalai, V., Hari Sundar, G. V., Shivaprasad, P. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+conserved+sequence+signature+is+essential+for+robust+plant+miRNA+biogenesis.">A conserved sequence signature is essential for robust plant miRNA biogenesis.</a> Nucleic Acids Research. , (2020).</li><li>Chen, H. 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=22-Nucleotide+RNAs+trigger+secondary+siRNA+biogenesis+in+plants.">22-Nucleotide RNAs trigger secondary siRNA biogenesis in plants.</a> Proceedings of the National Academy of Sciences of the United States of America. 107, 15269-15274 (2010).</li><li>Shivaprasad, P. V., 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+microRNA+superfamily+regulates+nucleotide+binding+site-leucine-rich+repeats+and+other+mRNAs.">A microRNA superfamily regulates nucleotide binding site-leucine-rich repeats and other mRNAs.</a> Plant Cell. 24, 859-874 (2012).</li><li>Shivaprasad, P. V., Dunn, R. M., Santos, B. A., Bassett, A., Baulcombe, D. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraordinary+transgressive+phenotypes+of+hybrid+tomato+are+influenced+by+epigenetics+and+small+silencing+RNAs.">Extraordinary transgressive phenotypes of hybrid tomato are influenced by epigenetics and small silencing RNAs.</a> The EMBO Journal. 31, 257-266 (2012).</li><li>Akbergenov, R., 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=Molecular+characterization+of+geminivirus-derived+small+RNAs+in+different+plant+species.">Molecular characterization of geminivirus-derived small RNAs in different plant species.</a> Nucleic Acids Research. 34, 462-471 (2006).</li><li>Tirumalai, V., Swetha, C., Nair, A., Pandit, A., Shivaprasad, P. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=miR828+and+miR858+regulate+VvMYB114+to+promote+anthocyanin+and+flavonol+accumulation+in+grapes.">miR828 and miR858 regulate VvMYB114 to promote anthocyanin and flavonol accumulation in grapes.</a> Journal of Experimental Botany. , (2019).</li><li>Li, C., Zamore, P. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+Small+RNAs+by+Northern+Hybridization.">Analysis of Small RNAs by Northern Hybridization.</a> Cold Spring Harbor Protocols. (8), (2018).</li><li>Swetha, 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=Major+domestication-related+phenotypes+in+indica+rice+are+due+to+loss+of+miRNA-mediated+laccase+silencing.">Major domestication-related phenotypes in indica rice are due to loss of miRNA-mediated laccase silencing.</a> The Plant Cell. , (2018).</li></ol>

No conflicts of interests declared.

This method can be extensively used for detection and quantification of small RNAs including less abundant miRNAs. The protocol mainly describes the steps for denaturing the total RNA in a loading buffer, size separation by gel electrophoresis, transfer of RNA to a membrane, cross-link the RNA onto membrane and hybridize using desired radiolabeled oligo probes.
The critical step for any blotting experiment is the use of good quality RNA for sample preparation. Before loading the gels, one must...

The recent discovery of small regulatory RNAs, microRNAs, has led research in understanding them and their role in plants and animals1. Long precursors of miRNAs are processed into 21 to 24 nt mature miRNAs by HYL1 and specific dicer-like proteins2,3. A 22 nt miRNA can initiate cascade silencing by generating secondary siRNAs4. Studies have shown the role of miRNAs and secondary siRNAs in development, cell fate and stress responses5,6.
Northern hybridization is an experimental method routinely employed to detect specific RNA molecules. This method customizes its use in the detection of approximately 19 -24 nt long small RNAs from a pool of total RNAs7. In this demonstration, we illustrate the use of this technique for the detection and quantification of miRNAs. This method uses labelling of probes using radioisotopes; thus, miRNA levels in the sample can be detected with increased sensitivity. Unlike PCR-based methods, this method ensures quantification of expression as well as size determination of the miRNAs. In this protocol, we show crucial steps that improve miRNA detection. We have modified steps in blotting and hybridization for obtaining high resolution signal detection of miRNAs. This technique can also be used for the detection other endogenous small RNAs such as siRNAs, tasi-secondary RNAs and snoRNAs.

<table>
	<tbody>
		<tr>
			<td>40% Acrylamide-bisacrylamide solution</td>
			<td>Sigma</td>
			<td>A9926</td>
			<td></td>
		</tr>
		<tr>
			<td>Ammonium persulphate (APS)</td>
			<td>BioRad</td>
			<td>1610700</td>
			<td></td>
		</tr>
		<tr>
			<td>Blotting paper</td>
			<td>whatmann blotting paper I</td>
			<td>1001-125</td>
			<td></td>
		</tr>
		<tr>
			<td>Bromophenol blue</td>
			<td>Sigma</td>
			<td>B5525-5G</td>
			<td></td>
		</tr>
		<tr>
			<td>Capillary loading tips</td>
			<td>BioRad</td>
			<td>2239915</td>
			<td></td>
		</tr>
		<tr>
			<td>Deionized formamide</td>
			<td>Ambion</td>
			<td>AM9342</td>
			<td></td>
		</tr>
		<tr>
			<td>Heating block</td>
			<td>Eppendorff</td>
			<td>5350</td>
			<td></td>
		</tr>
		<tr>
			<td>Hybond N+nylon membrane</td>
			<td>GE</td>
			<td>RPN203B</td>
			<td></td>
		</tr>
		<tr>
			<td>Hybridization bottle</td>
			<td>Sigma</td>
			<td>Z374792-1EA</td>
			<td></td>
		</tr>
		<tr>
			<td>Hybridization Oven</td>
			<td>Thermo Scientific</td>
			<td>1211V79</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N,N&#8217;,N&#8217;-Tetramethylethylenediamine (TEMED)</td>
			<td>Sigma</td>
			<td>T7024-25ml</td>
			<td></td>
		</tr>
		<tr>
			<td>PhosphorImager</td>
			<td>GE- Typhoon scanner</td>
			<td>29187194</td>
			<td></td>
		</tr>
		<tr>
			<td>PhosphorImager screen and cassette</td>
			<td>GE healthcare</td>
			<td>GE28-9564-75</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipettes</td>
			<td>Gilson, models: P20 and P10</td>
			<td>FA10002M, FA10003M</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic pipette</td>
			<td>Falcon</td>
			<td>357550</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyacrylamide gel apparatus</td>
			<td>BioRad</td>
			<td>1658003EDU</td>
			<td></td>
		</tr>
		<tr>
			<td>Sephadex G-25 column</td>
			<td>GE healthcare</td>
			<td>27532501</td>
			<td></td>
		</tr>
		<tr>
			<td>Speed Vac Concentrator</td>
			<td>Thermo Scientific</td>
			<td>20-548-130</td>
			<td></td>
		</tr>
		<tr>
			<td>Spinwin</td>
			<td>Tarsons</td>
			<td>1010</td>
			<td></td>
		</tr>
		<tr>
			<td>T4 Polynucleotide Kinase (PNK)</td>
			<td>NEB</td>
			<td>M0201S</td>
			<td></td>
		</tr>
		<tr>
			<td>Transblot apparatus</td>
			<td>BioRad</td>
			<td>1703946</td>
			<td></td>
		</tr>
		<tr>
			<td>ULTRAHyb hybridization buffer</td>
			<td>Ambion</td>
			<td>AM8670</td>
			<td></td>
		</tr>
		<tr>
			<td>Urea</td>
			<td>Fischer Scientific</td>
			<td>15985</td>
			<td></td>
		</tr>
		<tr>
			<td>UV-crosslinker</td>
			<td>UVP</td>
			<td>CL-1000L</td>
			<td></td>
		</tr>
		<tr>
			<td>Vortex</td>
			<td>Tarsons</td>
			<td>3020</td>
			<td></td>
		</tr>
		<tr>
			<td>Water bath</td>
			<td>NEOLAB</td>
			<td>D-8810</td>
			<td></td>
		</tr>
		<tr>
			<td>Xylene cyanol</td>
			<td>Sigma</td>
			<td>X4126-10G</td>
			<td></td>
		</tr>
	</tbody>
</table>

rna blot analysis for the detection and quantification of plant micrornas

MicroRNAs (miRNAs) are a class of endogenously expressed non-coding, ~21 nt small RNAs involved in the regulation of gene expression in both plants and animals. Most miRNAs act as negative switches of gene expression targeting key genes. In plants, primary miRNAs (pri-miRNAs) transcripts are generated by RNA polymerase II, and they form varying lengths of stable stem-loop structures called pre-miRNAs. An endonuclease, Dicer-like1, processes the pre-miRNAs into miRNA-miRNA* duplexes. One of the strands from miRNA-miRNA* duplex is selected and loaded onto Argonaute 1 protein or its homologs to mediate the cleavage of target mRNAs. Although miRNAs are key signaling molecules, their detection is often carried out by less than optimal PCR-based methods instead of a sensitive northern blot analysis. We describe a simple, reliable, and extremely sensitive northern method that is ideal for the quantification of miRNA levels with very high sensitivity, literally from any plant tissue. Additionally, this method can be used to confirm the size, stability and the abundance of miRNAs and their precursors.

In this demonstration, we have detected and quantified the expression of miR397 in different tissues of indica rice var whiteponni (Figure 1). miR397 is a 22 nt miRNA and conserved miRNA. The expression of miR397 can be detected in all the tested samples. As per the next-generation sequencing data, sample 1 (seedling tissue) has miR397 at 5 reads per million (rpm). We detected its signal comfortably, indicating that the method is very sensitive and can be used to detect eve...

Watch this Scientific Journal Video about RNA Blot Analysis for the Detection and Quantification of Plant MicroRNAs at JoVE.com

RNA Blot Analysis for the Detection and Quantification of Plant MicroRNAs

This method demonstrates use of the northern hybridization technique to detect miRNAs from total RNA extract.

MicroRNAs (miRNAs) are a class of endogenously expressed non-coding, ~21 nt small RNAs involved in the regulation of gene expression in both plants and ...

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Biochemistry

10.5K Views.  Tata Institute of Fundamental Research. This method demonstrates use of the northern hybridization technique to detect miRNAs from total RNA extract.

Video: RNA Blot Analysis for the Detection and Quantification of Plant MicroRNAs

Isolation of High-density Lipoproteins for Non-coding Small RNA Quantification

The diversity of small non-coding RNAs (sRNA) is rapidly expanding and their roles in biological processes, including gene regulation, are emerging. Most interestingly, sRNAs are also found outside of cells and are stably present in all biological fluids. As such, extracellular sRNAs represent a novel class of disease biomarkers and are likely involved in cell signaling and intercellular communication networks. To assess their potential as biomarkers, sRNAs can be quantified in plasma, urine, and other fluids. Nevertheless, to fully understand the impact of extracellular sRNAs as endocrine signals, it is important to determine which carriers are transporting and protecting them in biological fluids (e.g., plasma), which cells and tissues contribute to extracellular sRNA pools, and cells and tissues capable of accepting and utilizing extracellular sRNA. To accomplish these goals, it is critical to isolate highly pure populations of extracellular carriers for sRNA profiling and quantification. We have previously demonstrated that lipoproteins, particularly high-density lipoproteins (HDL), transport functional microRNAs (miRNA) between cells and HDL-miRNAs are significantly altered in disease. Here, we detail a new protocol that utilizes tandem HDL isolation with density-gradient ultracentrifugation (DGUC) and fast-protein-liquid chromatography (FPLC) to obtain highly pure HDL for downstream profiling and quantification of all sRNAs, including miRNAs, using both high-throughput sequencing and real-time PCR approaches. This protocol will be a valuable resource for the investigation of sRNAs on HDL.

This protocol describes the isolation and quantification of high-density lipoprotein small RNAs.

The diversity of small non-coding RNAs (sRNA) is rapidly expanding and their roles in biological processes, including gene regulation, are emerging. Most ...

Experimental Design for Laser Microdissection RNA-Seq: Lessons from an Analysis of Maize Leaf Development

Genes with important roles in development frequently have spatially and/or temporally restricted expression patterns. Often these gene transcripts are not detected or are not identified as differentially expressed (DE) in transcriptomic analyses of whole plant organs. Laser Microdissection RNA-Seq (LM RNA-Seq) is a powerful tool to identify genes that are DE in specific developmental domains. However, the choice of cellular domains to microdissect and compare, and the accuracy of the microdissections are crucial to the success of the experiments. Here, two examples illustrate design considerations for transcriptomics experiments; a LM RNA-seq analysis to identify genes that are DE along the maize leaf proximal-distal axis, and a second experiment to identify genes that are DE in liguleless1-R (lg1-R) mutants compared to wild-type. Key elements that contributed to the success of these experiments were detailed histological and in situ hybridization analyses of the region to be analyzed, selection of leaf primordia at equivalent developmental stages, the use of morphological landmarks to select regions for microdissection, and microdissection of precisely measured domains. This paper provides a detailed protocol for the analysis of developmental domains by LM RNA-Seq. The data presented here illustrate how the region selected for microdissection will affect the results obtained.

Many developmentally important genes have cell- or tissue-specific expression patterns. This paper describes LM RNA-seq experiments to identify genes that are differentially expressed at the maize leaf blade-sheath boundary and in lg1-R mutants compared to wild-type. The experimental considerations discussed here apply to transcriptomic analyses of other developmental phenomena.

Genes with important roles in development frequently have spatially and/or temporally restricted expression patterns. Often these gene transcripts are not ...

An Efficient Method for the Isolation of Highly Purified RNA from Seeds for Use in Quantitative Transcriptome Analysis

Plant seeds accumulate large amounts of storage reserves comprising biodegradable organic matter. Humans rely on seed storage reserves for food and as industrial materials. Gene expression profiles are powerful tools for investigating metabolic regulation in plant cells. Therefore, detailed, accurate gene expression profiles during seed development are required for crop breeding. Acquiring highly purified RNA is essential for producing these profiles. Efficient methods are needed to isolate highly purified RNA from seeds. Here, we describe a method for isolating RNA from seeds containing large amounts of oils, proteins, and polyphenols, which have inhibitory effects on high-purity RNA isolation. Our method enables highly purified RNA to be obtained from seeds without the use of phenol, chloroform, or additional processes for RNA purification. This method is applicable to Arabidopsis, rapeseed, and soybean seeds. Our method will be useful for monitoring the expression patterns of low level transcripts in developing and mature seeds.

We have succeeded in establishing a method for RNA isolation from plant seeds containing large amounts of oils, proteins, and polyphenols, which have inhibitory effects on high-purity RNA isolation. Our method is suitable for monitoring the expression of genes with low level transcripts in seeds.

Plant seeds accumulate large amounts of storage reserves comprising biodegradable organic matter. Humans rely on seed storage reserves for food and as ...

A Simple Fractionated Extraction Method for the Comprehensive Analysis of Metabolites, Lipids, and Proteins from a Single Sample

Understanding of complex biological systems requires the measurement, analysis and integration of multiple compound classes of the living cell, usually determined by transcriptomic, proteomic, metabolomics and lipidomic measurements. In this protocol, we introduce a simple method for the reproducible extraction of metabolites, lipids and proteins from biological tissues using a single aliquot per sample. The extraction method is based on a methyl tert-butyl ether: methanol: water system for liquid: liquid partitioning of hydrophobic and polar metabolites into two immiscible phases along with the precipitation of proteins and other macromolecules as a solid pellet. This method, therefore, provides three different fractions of specific molecular composition, which are fully compatible with common high throughput 'omics' technologies such as liquid chromatography (LC) or gas chromatography (GC) coupled to mass spectrometers. Even though the method was initially developed for the analysis of different plant tissue samples, it has proved to be fully compatible for the extraction and analysis of biological samples from systems as diverse as algae, insects, and mammalian tissues and cell cultures.

A protocol for comprehensive extraction of lipids, metabolites and proteins from biological tissues using one sample is presented.

Understanding of complex biological systems requires the measurement, analysis and integration of multiple compound classes of the living cell, usually ...

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.

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 ...

Mouse Adipose Tissue Collection and Processing for RNA Analysis

Compared to other tissues, white adipose tissue has a considerably less RNA and protein content for downstream applications such as real-time PCR and Western Blot, since it mostly contains lipids. RNA isolation from adipose tissue samples is also challenging as extra steps are required to avoid these lipids. Here, we present a procedure to collect three anatomically different white adipose tissues from mice, to process these samples and perform RNA isolation. We further describe the synthesis of cDNA and gene expression experiments using real-time PCR. The hereby described protocol allows the reduction of contamination from the animal's hair and blood on fat pads as well as cross-contamination between different fat pads during tissue collection. It has also been optimized to ensure adequate quantity and quality of the RNA extracted. This protocol can be widely applied to any mouse model where adipose tissue samples are required for routine experiments such as real-time PCR but is not intended for isolation from primary adipocytes cell culture.

The purpose of this paper is to present a step-by-step procedure to collect different white adipose tissues from mice, process the fat samples and extract RNA.

Compared to other tissues, white adipose tissue has a considerably less RNA and protein content for downstream applications such as real-time PCR and ...

Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs

Translation initiation is the rate-limiting step of protein synthesis and represents a key point at which cells regulate their protein output. Regulation of protein synthesis is the key to cellular stress-response, and dysregulation is central to many disease states, such as cancer. For instance, although cellular stress leads to the inhibition of global translation by attenuating cap-dependent initiation, certain stress-response proteins are selectively translated in a cap-independent manner. Discreet RNA regulatory elements, such as cellular internal ribosome entry sites (IRESes), allow for the translation of these specific mRNAs. Identification of such mRNAs, and the characterization of their regulatory mechanisms, have been a key area in molecular biology. Toeprinting is a method for the study of RNA structure and function as it pertains to translation initiation. The goal of toeprinting is to assess the ability of in vitro transcribed RNA to form stable complexes with ribosomes under a variety of conditions, in order to determine which sequences, structural elements, or accessory factors are involved in ribosome binding&#8212;a pre-cursor for efficient translation initiation. Alongside other techniques, such as western analysis and polysome profiling, toeprinting allows for a robust characterization of mechanisms for the regulation of translation initiation.

Toeprinting aims to measure the ability of in vitro transcribed RNA to form translation initiation complexes with ribosomes under a variety of conditions. This protocol describes a method for toeprinting mammalian RNA and can be used to study both cap-dependent and IRES-driven translation.

Translation initiation is the rate-limiting step of protein synthesis and represents a key point at which cells regulate their protein output. Regulation ...

2 in 1: One-step Affinity Purification for the Parallel Analysis of Protein-Protein and Protein-Metabolite Complexes

Cellular processes are regulated by interactions between biological molecules such as proteins, metabolites, and nucleic acids. While the investigation of protein-protein interactions (PPI) is no novelty, experimental approaches aiming to characterize endogenous protein-metabolite interactions (PMI) constitute a rather recent development. Herein, we present a protocol that allows simultaneous characterization of the PPI and PMI of a protein of choice, referred to as bait. Our protocol was optimized for Arabidopsis cell cultures and combines affinity purification (AP) with mass spectrometry (MS)-based protein and metabolite detection. In short, transgenic Arabidopsis lines, expressing bait protein fused to an affinity tag, are first lysed to obtain a native cellular extract. Anti-tag antibodies are used to pull down protein and metabolite partners of the bait protein. The affinity-purified complexes are extracted using a one-step methyl tert-butyl ether (MTBE)/methanol/water method. Whilst metabolites separate into either the polar or the hydrophobic phase, proteins can be found in the pellet. Both metabolites and proteins are then analyzed by ultra-performance liquid chromatography-mass spectrometry (UPLC-MS or UPLC-MS/MS). Empty-vector (EV) control lines are used to exclude false positives. The major advantage of our protocol is that it enables identification of protein and metabolite partners of a target protein in parallel in near-physiological conditions (cellular lysate). The presented method is straightforward, fast, and can be easily adapted to biological systems other than plant cell cultures.

Protein-protein and protein-metabolite interactions are crucial for all cellular functions. Herein, we describe a protocol that allows parallel analysis of these interactions with a protein of choice. Our protocol was optimized for plant cell cultures and combines affinity purification with mass spectrometry-based protein and metabolite detection.

Cellular processes are regulated by interactions between biological molecules such as proteins, metabolites, and nucleic acids. While the investigation of ...

Using In Vitro Fluorescence Resonance Energy Transfer to Study the Dynamics Of Protein Complexes at a Millisecond Time Scale

Proteins are the primary operators of biological systems, and they usually interact with other macro- or small molecules to carry out their biological functions. Such interactions can be highly dynamic, meaning the interacting subunits are constantly associated and dissociated at certain rates. While measuring the binding affinity using techniques such as quantitative pull-down reveals the strength of the interaction, studying the binding kinetics provides insights on how fast the interaction occurs and how long each complex can exist. Furthermore, measuring the kinetics of an interaction in the presence of an additional factor, such as a protein exchange factor or a drug, helps reveal the mechanism by which the interaction is regulated by the other factor, providing important knowledge for the advancement of biological and medical research. Here, we describe a protocol for measuring the binding kinetics of a protein complex that has a high intrinsic association rate and can be dissociated quickly by another protein. The method uses fluorescence resonance energy transfer to report the formation of the protein complex in vitro, and it enables monitoring the fast association and dissociation of the complex in real time on a stopped-flow fluorimeter. Using this assay, the association and dissociation rate constants of the protein complex are quantified.

Protein-protein interactions are critical for biological systems, and studies of the binding kinetics provide insights into the dynamics and function of protein complexes. We describe a method that quantifies the kinetic parameters of a protein complex using fluorescence resonance energy transfer and the stopped-flow technique. &#160;

Proteins are the primary operators of biological systems, and they usually interact with other macro- or small molecules to carry out their biological ...

Studying RNA Interactors of Protein Kinase RNA-Activated during the Mammalian Cell Cycle

Protein kinase RNA-activated (PKR) is a member of the innate immune response proteins and recognizes the double-stranded secondary structure of viral RNAs. When bound to viral double-stranded RNAs (dsRNAs), PKR undergoes dimerization and subsequent autophosphorylation. Phosphorylated PKR (pPKR) becomes active and induces phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2&#945;) to suppress global translation. Increasing evidence suggests that PKR can be activated under physiological conditions such as during the cell cycle or under various stress conditions without infection. However, our understanding of the RNA activators of PKR is limited due to the lack of a standardized experimental method to capture and analyze PKR-interacting dsRNAs. Here, we present an experimental protocol to specifically enrich and analyze PKR bound RNAs during the cell cycle using HeLa cells. We utilize the efficient crosslinking activity of formaldehyde to fix PKR-RNA complexes and isolate them via immunoprecipitation. PKR co-immunoprecipitated RNAs can then be further processed to generate a high-throughput sequencing library. One major class of PKR-interacting cellular dsRNAs is mitochondrial RNAs (mtRNAs), which can exist as intermolecular dsRNAs through complementary interaction between the heavy-strand and the light-strand RNAs. To study the strandedness of these duplex mtRNAs, we also present a protocol for strand-specific qRT-PCR. Our protocol is optimized for the analysis of PKR-bound RNAs, but it can be easily modified to study cellular dsRNAs or RNA-interactors of other dsRNA binding proteins.

We present experimental approaches for studying RNA-interactors of double-stranded RNA binding protein kinase RNA-activated (PKR) during the mammalian cell cycle using HeLa cells. This method utilizes formaldehyde to crosslink RNA-PKR complexes and immunoprecipitation to enrich PKR-bound RNAs. These RNAs can be further analyzed through high-throughput sequencing or qRT-PCR.

Protein kinase RNA-activated (PKR) is a member of the innate immune response proteins and recognizes the double-stranded secondary structure of viral ...