Name: fluorescent visualization of mango-tagged rna in polyacrylamide gels via a poststaining method
Uploaded: 2019-06-21T12:30:00
Description: Watch this Scientific Journal Video about Fluorescent Visualization of Mango-tagged RNA in Polyacrylamide Gels via a Poststaining Method at JoVE.com

The authors thank Razvan Cojocaru and Amir Abdolahzadeh for their technical assistance and Lena Dolgosheina for proofreading the manuscript. Funding was provided for this project by a Canadian Natural Sciences and Engineering Research Council (NSERC) operating grant to P.J.U.

1. Preparation of the reagents
<ol>
	<li>TO1-Biotin poststaining solution (gel staining solution)
	<ol>
		<li>Make 1 L of 1 M phosphate buffer at pH 7.2 at 25 &#176;C by adding 342 mL of 1 M of Na2HPO4 and 158 mL of 1 M NaH2PO4. Adjust pH to 7.2 at 50 mM by adding the appropriate phosphate solution. Sterile-filter using a 0.2 &#181;m filter and store the solution in plasticware at room temperature.</li>
		<li>Prepare 5x gel staining solution (without TO1-Biot...

<ol>
	<li>Dolgosheina, E. 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=RNA+Mango+Aptamer-Fluorophore:+A+Bright,+High-Affinity+Complex+for+RNA+Labeling+and+Tracking.">RNA Mango Aptamer-Fluorophore: A Bright, High-Affinity Complex for RNA Labeling and Tracking.</a> ACS Chemical Biology. , (2014).</li><li>Autour, 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=Fluorogenic+RNA+Mango+aptamers+for+imaging+small+non-coding+RNAs+in+mammalian+cells.">Fluorogenic RNA Mango aptamers for imaging small non-coding RNAs in mammalian cells.</a> Nature Communications. 9, 656 (2018).</li><li>Dolgosheina, E. V., Unrau, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorophore-binding+RNA+aptamers+and+their+applications:+Fluorophore-binding+RNA+aptamers.">Fluorophore-binding RNA aptamers and their applications: Fluorophore-binding RNA aptamers.</a> Wiley Interdisciplinary Reviews: RNA. , (2016).</li><li>Panchapakesan, S. S., 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=Ribonucleoprotein+Purification+and+Characterization+using+RNA+Mango.">Ribonucleoprotein Purification and Characterization using RNA Mango.</a> RNA. , 1592-1599 (2017).</li><li>Trachman, R. 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=Structural+basis+for+high-affinity+fluorophore+binding+and+activation+by+RNA+Mango.">Structural basis for high-affinity fluorophore binding and activation by RNA Mango.</a> Nature Chemical Biology. 13, 807 (2017).</li><li>Trachman, R. 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=Crystal+Structures+of+the+Mango-II+RNA+Aptamer+Reveal+Heterogeneous+Fluorophore+Binding+and+Guide+Engineering+of+Variants+with+Improved+Selectivity+and+Brightness.">Crystal Structures of the Mango-II RNA Aptamer Reveal Heterogeneous Fluorophore Binding and Guide Engineering of Variants with Improved Selectivity and Brightness.</a> Biochemistry. 57, 3544-3548 (2018).</li><li>Trachman, 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=Mango-III+is+a+compact+fluorogenic+RNA+aptamer+of+unusual+structural+complexity.">Mango-III is a compact fluorogenic RNA aptamer of unusual structural complexity.</a> Nature Chemical Biology. , (2018).</li><li>Panchapakesan, S. S. S., Jeng, S. C. Y., Unrau, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RNA+complex+purification+using+high-affinity+fluorescent+RNA+aptamer+tags.">RNA complex purification using high-affinity fluorescent RNA aptamer tags.</a> Annals of the New York Academy of Sciences. , (2015).</li><li>Filonov, G. S., Kam, C. W., Song, W., Jaffrey, S. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In-gel+imaging+of+RNA+processing+using+Broccoli+reveals+optimal+aptamer+expression+strategies.">In-gel imaging of RNA processing using Broccoli reveals optimal aptamer expression strategies.</a> Chemistry &amp; Biology. 22, 649-660 (2015).</li><li>Milligan, J. F., Groebe, D. R., Witherell, G. W., Uhlenbeck, O. 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A significant advantage of the Mango fluorescent tag is that a single tag can be used in multiple ways. The high brightness and affinity of these aptamers make them useful not only for in cell visualization2 but also for in vitro RNA or RNP purification4. Therefore, gel imaging extends the versatility of the Mango tag in a straightforward way. Mango gel imaging sensitivity is slightly less than that of a northern blot14 but can easily detect 60&#8211...

Mango is an RNA tagging system consisting of a set of four small fluorescent RNA aptamers that bind tightly (nanomolar binding) to simple derivatives of the thiazole-orange (TO1-Biotin, Figure 1A)1,2,3. Upon binding, the fluorescence of this ligand is increased 1,000- to 4,000-fold depending on the specific aptamer. The high brightness of the Mango system, which for Mango III exceeds that of enhanced green fluorescent protein (eGFP), combined with the nanomolar binding affinity of the RNA Mango aptamers, allows it to be used both in the imaging and the purification of RNA complexes2,4.
The X-ray structures of Mango I5, II6, and III7 have been determined to high resolution, and all three aptamers utilize an RNA quadruplex to bind TO1-Biotin (Figure 1B&#8211;D). The compact cores of all three aptamers are isolated from the external RNA sequence via compact adaptor motifs. Mango I and II both utilize a flexible GNRA-like loop adaptor to connect their Mango cores to an arbitrary RNA duplex (Figure 1B,C). In contrast, Mango III uses a rigid triplex motif to connect its core to an arbitrary RNA helix (Figure 1D, purple residues), while the structure of Mango IV is not currently known. As the ligand-binding core of each of these aptamers is separated from the external RNA sequence by these helical adaptors, it appears likely that they can all be simply incorporated into a variety of RNAs. The bacterial 6S regulatory RNA (Mango I), components of the yeast spliceosome (Mango I), and the human 5S RNA, U6 RNA, and a C/D scaRNA (Mango II and IV) have all been successfully tagged in this fashion2,8, suggesting that many biological RNAs can be tagged using the RNA Mango aptamer system.
Denaturing and native gels are commonly used to study RNAs. Denaturing gels are often used to judge RNA size or RNA processing, but typically, in the case of a northern blot, for example, require several slow and sequential steps in order to generate an image. While other RNA fluorogenic aptamers, such as RNA Spinach and Broccoli, have been used successfully for gel imaging9, no fluorogenic aptamer system to date possesses the high brightness and affinity of the Mango system, making it of considerable interest to investigate Mango&#8217;s gel-imaging abilities. In this study, we wondered if the RNA Mango system could be simply extended to gel imaging, as the excitation and emission wavelengths of TO1-Biotin (510 nm and 535 nm, respectively) are appropriate for imaging in the eGFP channel common to most fluorescent gel-scanning instrumentation.
The post-gel staining protocol presented here provides a rapid way to specifically detect Mango-tagged RNA molecules in native and denaturing polyacrylamide gel electrophoresis (PAGE) gels. This staining method involves soaking gels in a buffer containing potassium and TO1-Biotin. RNA Mango aptamers are G-quadruplex based and potassium is required to stabilize such structures. Using RNA transcribed from minimal Mango-encoding DNA templates (see the protocol section), we can simply detect as little as little as 62.5 fmol of RNA in native gels and 125 fmol of RNA in denaturing gels, using a straightforward staining protocol. In contrast to common nonspecific nucleic acid stains (see Table of Materials, referred to SG from hereon), we can clearly identify Mango-tagged RNA even when high concentrations of total untagged RNA are present in the sample.

<table border="0" cellpadding="0" cellspacing="0" style="width:924px;" width="924">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">0.8mm Thick Comb 14 Wells for 30 mL PAGE gels</td>
			<td style="width:192px;">LabRepCo</td>
			<td style="width:147px;">11956042</td>
			<td style="width:275px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">101-1000 &#181;L&#160; tips</td>
			<td>Fisher</td>
			<td>02-707-511</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">20-200 &#181;L low retention&#160; tips</td>
			<td>Fisher Scientific</td>
			<td>02-717-143</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Acrylamide:N,N&#39;-methylenebisacrylamide (40% 19:1)</td>
			<td>Bioreagents</td>
			<td>BP1406-1</td>
			<td>Acute toxicity</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Acrylamide:N,N&#39;-methylenebisacrylamide (40% 29:1)</td>
			<td>Fisher</td>
			<td>BP1408-1</td>
			<td>Acute toxicity</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Agar</td>
			<td>Anachemia</td>
			<td>02116-380</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Aluminium backed TLC plate</td>
			<td>Sigma-Aldrich</td>
			<td>1164840001</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Amersham Imager 600</td>
			<td>GE Healthcare Lifesciences</td>
			<td>29083461</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ammonium Persulfate</td>
			<td>Biorad</td>
			<td>161-0700</td>
			<td>Harmful</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">BL21 cells</td>
			<td>NEB</td>
			<td>C2527H</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Boric Acid</td>
			<td>ACP</td>
			<td>B-2940</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bromophenol Blue sodium salt</td>
			<td>Sigma</td>
			<td>B8026-25G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Chloloform</td>
			<td>ACP</td>
			<td>C3300</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dithiothreitol</td>
			<td>Sigma Aldrich Alcohols</td>
			<td>D0632-5G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DNase I</td>
			<td>ThermoFisher</td>
			<td>EN0525</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">EDTA Disodium Salt</td>
			<td>ACP</td>
			<td>E-4320</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethanol</td>
			<td>Commerial&#160;</td>
			<td>P016EAAN</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Flat Gel Loading tips</td>
			<td>Costar</td>
			<td>CS004854</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Formamide 99%</td>
			<td>Alfa Aesar</td>
			<td>A11076</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Gel apparatus set with spacers and combs</td>
			<td>LabRepCo</td>
			<td>41077017</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glass Dish with Plastic lid</td>
			<td>Pyrex</td>
			<td>1122963</td>
			<td style="width:275px;">Should be large enough to fit your gel piece</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glycerol</td>
			<td>Anachemia</td>
			<td>43567-540</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">HCl</td>
			<td>Anachemia</td>
			<td>464140468</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ImageQuanTL</td>
			<td>GE Healthcare Lifesciences</td>
			<td>29000605</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">IPTG</td>
			<td>Invitrogen</td>
			<td>15529-019</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">KCl</td>
			<td>ACP</td>
			<td>P-2940</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">MgCl2</td>
			<td>Caledron</td>
			<td>4903-01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">MgSO4</td>
			<td>Sigma-Aldrich</td>
			<td>M3409</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NaCl</td>
			<td>ACP</td>
			<td>S-2830</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">NaOH</td>
			<td>BDH</td>
			<td>BDH9292</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Orbital Rotator</td>
			<td>Lab-Line</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Phenol</td>
			<td>Invitrogen</td>
			<td>15513-039</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Round Gel Loading tips</td>
			<td>Costar</td>
			<td>CS004853</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Phosphate dibasic</td>
			<td>Caledron</td>
			<td>8120-1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Phosphate monobasic</td>
			<td>Caledron</td>
			<td>8180-01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SYBRGold</td>
			<td>ThermoFisher</td>
			<td>S11494</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">T7 RNA Polymerase</td>
			<td>ABM</td>
			<td>E041</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TEMED</td>
			<td>Sigma-Aldrich</td>
			<td>T7024-50 ml</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TO1-3PEG-Biotin Fluorophore</td>
			<td>ABM</td>
			<td>G955</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tris Base</td>
			<td>Fisher</td>
			<td>BP152-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tryptone</td>
			<td>Fisher</td>
			<td>BP1421-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tween-20</td>
			<td>Sigma</td>
			<td>P9496-100</td>
			<td></td>
		</tr>
		<tr height="23">
			<td height="23" style="height:23px;">Urea</td>
			<td>Fisher</td>
			<td>U15-3</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Xylene Cyanol</td>
			<td>Sigma</td>
			<td>X4126-10G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Yeast Extract</td>
			<td>Bioshop</td>
			<td>YEX401.500</td>
			<td></td>
		</tr>
	</tbody>
</table>

fluorescent visualization of mango-tagged rna in polyacrylamide gels via a poststaining method

Native and denaturing polyacrylamide gels are routinely used to characterize ribonucleoprotein (RNP) complex mobility and to measure RNA size, respectively. As many gel-imaging techniques use nonspecific stains or expensive fluorophore probes, sensitive, discriminating, and economical gel-imaging methodologies are highly desirable. RNA Mango core sequences are small (19&#8211;22 nt) sequence motifs that, when closed by an arbitrary RNA stem, can be simply and inexpensively appended to an RNA of interest. These Mango tags bind with high affinity and specificity to a thiazole-orange fluorophore ligand called TO1-Biotin, which becomes thousands of times more fluorescent upon binding. Here we show that Mango I, II, III, and IV can be used to specifically image RNA in gels with high sensitivity. As little as 62.5 fmol of RNA in native gels and 125 fmol of RNA in denaturing gels can be detected by soaking gels in an imaging buffer containing potassium and 20 nM TO1-Biotin for 30 min. We demonstrate the specificity of the Mango-tagged system by imaging a Mango-tagged 6S bacterial RNA in the context of a complex mixture of total bacterial RNA.

Short Mango-tagged RNAs were prepared as described in the protocol section. Assuming that fluorescence in denaturing conditions would be most difficult to observe owing to the presence of urea in the gels, we first studied the resistance of the Mango aptamers to urea, which acts as a nucleic acid denaturant. We found that Mango aptamers are substantially resistant to denaturation up to a urea concentration of approximately 1 M (Figure 2A). Prior to adding gel staining sol...

Watch this Scientific Journal Video about Fluorescent Visualization of Mango-tagged RNA in Polyacrylamide Gels via a Poststaining Method at JoVE.com

Fluorescent Visualization of Mango-tagged RNA in Polyacrylamide Gels via a Poststaining Method

Here we present a sensitive, rapid, and discriminating post-gel staining method to image RNAs tagged with RNA Mango aptamers I, II, III, or IV, using either native or denaturing polyacrylamide gel electrophoresis (PAGE) gels. After running standard PAGE gels, Mango-tagged RNA can be easily stained with TO1-Biotin and then analyzed using commonly available fluorescence readers.

Native and denaturing polyacrylamide gels are routinely used to characterize ribonucleoprotein (RNP) complex mobility and to measure RNA size, ...

The Mango-tagged gel imaging methodology demonstrated here is robust and is anticipated to be able to be simply extended in terms of sensitivity and specificity. This would further simplify the routine purification of biologically important RNAs and RNA complexes by the simple expedient of adding a Mango-tag to the RNA of interest. RNAs are being implicated in more and more diseases therefor this post dating method is an easy and fast way to be able to track and visualize RNA.Extra care will be required in transferring the gel from one place to another as the gels are fragile and prone to breaking. To prepare a 30 milliliter denaturing gel, first select the polyacrylamide percentage with the appropriate Bromophenol blue, and xylene cyanol dyes compared to an RNA of interest to insure high band separation. Then, mix solutions A, B, and C according to table one and add APS and timud.Immediately pour the gel solution into an appropriate gel casting apparatus. Insert the desired cone and leave the gel to polymerase for approximately 30 minutes. Make up the gel tank using 1 XTBE solution and carefully remove the cone.Carefully lift up the gel and mount on to the gel apparatus and secure using binder clips. Using a syringe, aspirate out the wells immediately prior to sample loading. Prepare 1X RNA samples by adding 2X denaturing gel loading solution to the RNA samples of interest.Use a thermocycler to heat the samples at 95 degrees Celsius for five minutes. Then, load cooled samples to the bottom of each well using gel loading tips. And well the gel at room temperature ensuring the power is effectively low to not crack the glass plate of the gel apparatus.Prepare 1X gel staining solution according to the manuscript in a clean glass container that is wide enough to comfortably fit the gel. Add enough 1X gel staining solution to the container so that the gel is completely covered with the solution when it is placed on an orbital rotator. Once the gel finishes running, remove the gel from the apparatus, cut off its'wells, and a corner of the gel in order to help determine the orientation.Then, carefully transfer the gel into the 1X gel staining solution. To perform the imaging, carefully decant the staining solution and rinse the gel quickly with water. Finally, carefully transfer the gel onto the tray to be placed in the imager.Roll a glass pipette over the gel to remove trapped bubbles and excess liquid. And proceed to taking a gel image. Mango aptamers one, two, three, four were substantially resist to denaturation up to approximately one molar Urea concentration.20 to 40 minute staining time was sufficient for maximum gel florescence. Longer time was not suitable for small RNAs used in this study as they started to diffuse out of the gel. Fluorometer analysis showed that Mango aptamers one, two, and three in the presence of Urea could fold more rapidly than aptamer four.In the absence of Urea, folding was much more rapid as was expected. The sensitivity of the post staining method was shown by single bands corresponding to well folded RNAs for each of the Mango variants in native and denaturing gels with a slightly less sensitivity for the later one. Quantification of native gels was log linear over about one order of magnitude with Mango one, two, and four behaving in a more linear fashion than Mango three.Quantification of denaturing gels were more linear suggesting that the presence of Urea in the denaturing gel might provide a more homogenous way to fold the aptamers once they are placed in the TO1 biotin staining solution. Mango tagged RNAs can be detected in the presence of total RNA using TO1 biotin staining compared to SG staining. Remember to make sure that the gel staining container is large enough to fit the gel otherwise the gel may fold on to itself.The RNA samples will transfer from one place to another. Similar to the denaturing gels, this method can be performed for a native gel. Run the gel in a cold room at a lower wattage to maintain native conditions.

fluorescent-visualization-mango-tagged-rna-polyacrylamide-gels-via

Research

JoVE Journal

Biochemistry

A Method for Measuring RNA N6-methyladenosine Modifications in Cells and Tissues

N6-Methyladenosine (m6A) modifications of RNA are diverse and ubiquitous amongst eukaryotes. They occur in mRNA, rRNA, tRNA, and microRNA. Recent studies have revealed that these reversible RNA modifications affect RNA splicing, translation, degradation, and localization. Multiple physiological processes, like circadian rhythms, stem cell pluripotency, fibrosis, triglyceride metabolism, and obesity are also controlled by m6A modifications. Immunoprecipitation/sequencing, mass spectrometry, and modified northern blotting are some of the methods commonly employed to measure m6A modifications. Herein, we present a northeastern blotting technique for measuring m6A modifications. The current protocol provides good size separation of RNA, better accommodation and standardization for various experimental designs, and clear delineation of m6A modifications in various sources of RNA. While m6A modifications are known to have a crucial impact on human physiology relating to circadian rhythms and obesity, their roles in other (patho)physiological states are unclear. Therefore, investigations on m6A modifications have immense possibility to provide key insights into molecular physiology.

A Method for Measuring RNA N6-methyladenosine Modifications in Cells and Tissues

A modified northern blotting method for measuring N6-methyladenosine (m6A) modifications in RNA is described. The current method can detect modifications in diverse RNAs and controls under various experimental designs.

N6-Methyladenosine (m6A) modifications of RNA are diverse and ubiquitous amongst eukaryotes. They occur in mRNA, rRNA, tRNA, and microRNA. Recent studies ...

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 ...

Detection and Visualization of DNA Damage-induced Protein Complexes in Suspension Cell Cultures Using the Proximity Ligation Assay

The DNA damage response orchestrates the repair of DNA lesions that occur spontaneously, are caused by genotoxic stress, or appear in the context of programmed DNA breaks in lymphocytes. The Ataxia-Telangiectasia Mutated kinase (ATM), ATM- and Rad3-Related kinase (ATR) and the catalytic subunit of DNA-dependent Protein Kinase (DNA-PKcs) are among the first that are activated upon induction of DNA damage, and are central regulators of a network that controls DNA repair, apoptosis and cell survival. As part of a tumor-suppressive pathway, ATM and ATR activate p53 through phosphorylation, thereby regulating the transcriptional activity of p53. DNA damage also results in the formation of so-called ionizing radiation-induced foci (IRIF) that represent complexes of DNA damage sensor and repair proteins that accumulate at the sites of DNA damage, which are visualized by fluorescence microscopy. Co-localization of proteins in IRIFs, however, does not necessarily imply direct protein-protein interactions, as the resolution of fluorescence microscopy is limited. 
In situ Proximity Ligation Assay (PLA) is a novel technique that allows the direct visualization of protein-protein interactions in cells and tissues with unprecedented specificity and sensitivity. This technique is based on the spatial proximity of specific antibodies binding to the proteins of interest. When the interrogated proteins are within ~40 nm an amplification reaction is triggered by oligonucleotides that are conjugated to the antibodies, and the amplification product is visualized by fluorescent labeling, yielding a signal that corresponds to the subcellular location of the interacting proteins. Using the established functional interaction between ATM and p53 as an example, it is demonstrated here how PLA can be used in suspension cell cultures to study the direct interactions between proteins that are integral parts of the DNA damage response.

Here, it is demonstrated how the in situ Proximity Ligation Assay (PLA) can be used to detect and visualize the direct protein-protein interactions between ATM and p53 in suspension cell cultures exposed to genotoxic stress.

The DNA damage response orchestrates the repair of DNA lesions that occur spontaneously, are caused by genotoxic stress, or appear in the context of ...

Sample Preparation for Mass Spectrometry-based Identification of RNA-binding Regions

Noncoding RNAs play important roles in several nuclear processes, including regulating gene expression, chromatin structure, and DNA repair. In most cases, the action of noncoding RNAs is mediated by proteins whose functions are in turn regulated by these interactions with noncoding RNAs. Consistent with this, a growing number of proteins involved in nuclear functions have been reported to bind RNA and in a few cases the RNA-binding regions of these proteins have been mapped, often through laborious, candidate-based methods.
Here, we report a detailed protocol to perform a high-throughput, proteome-wide unbiased identification of RNA-binding proteins and their RNA-binding regions. The methodology relies on the incorporation of a photoreactive uridine analog in the cellular RNA, followed by UV-mediated protein-RNA crosslinking, and mass spectrometry analyses to reveal RNA-crosslinked peptides within the proteome. Although we describe the procedure for mouse embryonic stem cells, the protocol should be easily adapted to a variety of cultured cells.

We describe a protocol to identify RNA-binding proteins and map their RNA-binding regions in live cells using UV-mediated photocrosslinking and mass spectrometry.

Noncoding RNAs play important roles in several nuclear processes, including regulating gene expression, chromatin structure, and DNA repair. In most ...

A Colorimetric Method for Measuring Iron Content in Plants

Iron, one of the most important micronutrients in living organisms, is involved in basic processes, such as respiration and photosynthesis. Iron content is rather low in all organisms, amounting in plants to about 0.009% of dry weight. To date, one of the most accurate methods for measuring iron concentration in plant tissues is flame absorption atomic spectroscopy. However, this approach is time-consuming and expensive and requires specific equipment not commonly found in plant laboratories. Therefore, a simpler, yet accurate method that can be routinely used is needed. The colorimetric Prussian Blue method is regularly used for qualitative iron staining in animal and plant histological sections. In this study, we adapted the Prussian Blue method for quantitative measurements of iron in tobacco leaves. We validated the accuracy of this method using both atomic spectroscopy and Prussian Blue staining to measure iron content in the same samples and found a linear regression (R2 = 0.988) between the two procedures. We conclude that the Prussian Blue method for quantitative iron measurement in plant tissues is precise, simple, and inexpensive. However, the linear regression presented here may not be appropriate for other plant species, due to potential interactions between the sample and the reagent. Establishment of a regression curve is thus needed for different plant species.

We present a simple and reliable protocol for measuring iron content in plant tissues using the colorimetric Prussian Blue method.

Iron, one of the most important micronutrients in living organisms, is involved in basic processes, such as respiration and photosynthesis. Iron content ...

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 ...

Fluorescent Silver Staining of Proteins in Polyacrylamide Gels

Silver staining is a colorimetric technique widely used to visualize protein bands in polyacrylamide gels following sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The classic silver stains have certain drawbacks, such as high background staining, poor protein recovery, low reproducibility, a narrow linear dynamic range for quantification, and limited compatibility with mass spectrometry (MS). Now, with the use of a fluorogenic Ag+ probe, TPE-4TA, we developed a fluorescent silver staining method for the total protein visualization in polyacrylamide gels. This new stain avoids the troublesome silver reduction step in traditional silver stains. Moreover, the fluorescent silver stain demonstrates good reproducibility, sensitivity, and linear quantification in protein detection, making it a useful and practical protein gel stain.

Here, we describe a detailed protocol outlining a new fluorescent staining technique for total protein detection in polyacrylamide gels. The protocol utilizes a silver ion-specific fluorescence turn-on probe, which detects Ag+-protein complexes, and eliminates certain limitations of traditional chromogenic silver stains.

Silver staining is a colorimetric technique widely used to visualize protein bands in polyacrylamide gels following sodium dodecyl sulfate-polyacrylamide ...

Use of Recombinant Fusion Proteins in a Fluorescent Protease Assay Platform and Their In-gel Renaturation

Proteases are intensively studied enzymes due to their essential roles in several biological pathways of living organisms and in pathogenesis; therefore, they are important drug targets. We have developed a magnetic-agarose-bead-based assay platform for the investigation of proteolytic activity, which is based on the use of recombinant fusion protein substrates. In order to demonstrate the use of this assay system, a protocol is presented on the example of human immunodeficiency virus type 1 (HIV-1) protease. The introduced assay platform can be utilized efficiently in the biochemical characterization of proteases, including enzyme activity measurements in mutagenesis, kinetic, inhibition, or specificity studies, and it may be suitable for high-throughput substrate screening or may be adapted to other proteolytic enzymes.
In this assay system, the applied substrates contain N-terminal hexahistidine (His6) and maltose-binding protein (MBP) tags, cleavage sites for tobacco etch virus (TEV) and HIV-1 proteases, and a C-terminal fluorescent protein. The substrates can be efficiently produced in Escherichia coli cells and easily purified using nickel (Ni)-chelate-coated beads. During the assay, the proteolytic cleavage of bead-attached substrates leads to the release of fluorescent cleavage fragments, which can be measured by fluorimetry. Additionally, cleavage reactions can be analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A protocol for the in-gel renaturation of assay components is also described, as partial renaturation of fluorescent proteins enables their detection based on molecular weight and fluorescence.

Here, we present the detailed procedure of a recently developed protease assay platform utilizing N-terminal hexahistidine/maltose-binding protein and fluorescent protein-fused recombinant substrates attached to the surface of nickel-nitrilotriacetic acid magnetic agarose beads. A subsequent in-gel analysis of the assay samples separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis is also presented.

Proteases are intensively studied enzymes due to their essential roles in several biological pathways of living organisms and in pathogenesis; therefore, ...

Monitoring Protein-RNA Interaction Dynamics In Vivo at High Temporal Resolution Using &#967;CRAC

The interaction between RNA-binding proteins (RBPs) and their RNA substrates exhibits fluidity and complexity. Within its lifespan, a single RNA can be bound by many different RBPs that will regulate its production, stability, activity, and degradation. As such, much has been done to understand the dynamics that exist between these two types of molecules. A particularly important breakthrough came with the emergence of &#8216;cross-linking and immunoprecipitation&#8217; (CLIP). This technique allowed stringent investigation into which RNAs are bound by a particular RBP. In short, the protein of interest is UV cross-linked to its RNA substrates in vivo, purified under highly stringent conditions, and then the RNAs covalently cross-linked to the protein are converted into cDNA libraries and sequenced. Since its conception, many derivative techniques have been developed in order to make CLIP amenable to particular fields of study. However, cross-linking using ultraviolet light is notoriously inefficient. This results in extended exposure times that make the temporal study of RBP-RNA interactions impossible. To overcome this issue, we recently designed and built much-improved UV irradiation and cell harvesting devices. Using these new tools, we developed a protocol for time-resolved analyses of RBP-RNA interactions in living cells at high temporal resolution: Kinetic CRoss-linking and Analysis of cDNAs (&#967;CRAC). We recently used this technique to study the role of yeast RBPs in nutrient stress adaptation. This manuscript provides a detailed overview of the &#967;CRAC method and presents recent results obtained with the Nrd1 RBP.

Kinetic cross-linking and analysis of cDNA is a method that allows investigation of the dynamics of protein-RNA interactions in living cells at high temporal resolution. Here the protocol is described in detail, including the growth of yeast cells, UV cross-linking, harvesting, protein purification, and next generation sequencing library preparation steps.

The interaction between RNA-binding proteins (RBPs) and their RNA substrates exhibits fluidity and complexity. Within its lifespan, a single RNA can be ...

Rapid and Cost-Effective RNA Extraction of Rat Pancreatic Tissue

Regardless of the extraction method, optimized RNA extraction of tissues and cell lines are carried out in four stages: 1) homogenization, 2) effective denaturation of proteins from RNA, 3) ribonuclease inactivation, and 4) removal of contamination from DNA, proteins, and carbohydrates. However, it is very laborious to maintain the integrity of RNA when there are high levels of RNase in the tissue. Spontaneous autolysis makes it very difficult to extract RNA from pancreatic tissue without damaging it. Thus, a practical RNA extraction method is needed to maintain the integrity of pancreatic tissues during the extraction process. An experimental and comparative study of existing protocols was carried out by obtaining 20-30 mg of rat pancreatic tissues in less than 2 minutes and extracting the RNA. The results were assessed by electrophoresis. The experiments were carried out three times for generalization of the results. Immersing pancreatic tissue in RNA stabilization reagent at -80 &#176;C for 24 h yielded high integrity RNA, when the RNA extraction reagent was used as the reagent. The results obtained were comparable to the results obtained from commercial kits with spin column bindings.

The purity and integrity of the isolated RNA is a vital step in RNA dependent assays. Here, we present a practical, rapid, and inexpensive method to extract RNA from a small quantity of undamaged pancreatic tissue.

Regardless of the extraction method, optimized RNA extraction of tissues and cell lines are carried out in four stages: 1) homogenization, 2) effective ...