S.V. is grateful for the funding support from the NIH K22AI077353 and the Landenberger Foundation. K.R. gratefully acknowledges funding from the NIH (5SC1GM083754).

<ol>
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The authors have nothing to disclose.

The in vitro pre-mRNA 3&#8217; cleavage reaction, carried out in HeLa cell nuclear extracts or with cleavage factors fractionated from these extracts, has enabled identification of the core cleavage factors and their main complexes16-21. Many more proteins associated with these factors have recently been identified22, and the in vitro reaction may continue to shed light on how these proteins contribute to the reaction. Perhaps because the reaction in vivo appears to be cot...

The biosynthesis of most mature eukaryotic message RNAs (mRNAs) requires several post-transcriptional modifications such as capping, splicing and polyadenylation. These modifications are generally coupled to ensure correct processing1 and strongly increase the stability of the mRNA.
The 3&#8217; end formation of mammalian pre-mRNAs is generated by endonucleolytic cleavage of the nascent RNA followed by addition of adenylate residues to the 5&#8217; cleaved product by poly(A) polymerase (PAP)2-4. In mammals, cleavage is accomplished by a multicomponent protein complex, of approximately 800 kDa, which assembles on specific pre-RNA sequences. The poly(A) signal sequence, a highly conserved canonical hexanucleotide sequence AAUAAA, directs the cleavage site at approximately 10-30 nt downstream. This site is specifically recognized by the cleavage and polyadenylation specificity factor (CPSF) and the 73 kD subunit of CSPF contains the endonuclease activity. The cleavage stimulation factor (CstF) binds a more degenerate GU- or U- rich element sequence downstream of the poly(A) site. Also required for cleavage is the mammalian cleavage factor I (CFIm), and the mammalian cleavage factor II (CFII). CFIm binds the specific UGUA(N) sites in upstream sequence elements (USEs) that have been defined for a number of genes and seem to be involved in important physiological processes5-8.
In vitro, RNA processing reactions are commonly analyzed by the use of radiolabeled RNA substrates9-12. These may be synthesized by run-off transcription from the bacteriophage promoter T7 or SP6. When studying a polyadenylation site that has not been characterized before, it is necessary to use genomic DNA rather than cDNA to generate the RNA substrate, as important downstream sequences might not be present in cDNA. Design substrates to include at least 150 nt upstream and 50 nt downstream from the cleavage site/end on the mature mRNA. The cleavage product migrates faster than the substrate; however, because other fragments may be generated by non-specific nuclease action, the specificity of the reaction has to be verified by its dependence on the correct processing signal sequences. Therefore, RNA substrates with a point mutation in the AAUAAA sequence (e.g. AAGAAA) serve as a negative control for the cleavage reaction.
Given that a small amount of radiolabeled RNA is used for the cleavage reactions, RNases present in high abundance in most nuclear extracts can be problematic, and limit the choice of the starting material for extract preparation. HeLa cells tend to contain low levels of endogenous RNases, and thus perform well in these assays.
The endonucleolytic cleavage of the RNA substrates in vivo and in vitro is immediately followed by the poly(A) addition, thus the cleaved intermediate is not present in detectable quantities. Therefore, to study either a specific RNA sequence or proteins involved in a cleavage reaction, experiments are done in conditions that prevent polyadenylation from occurring. There is no dependence of cleavage on polyadenylation, or vice versa, so one can stop polyadenylation without harming the cleavage reaction. Thus, ATP is replaced with a chain terminating analogue that lacks the 3&#8217; hydroxyl group so that only a single nucleotide can be incorporated at the poly(A) site and just cleaved RNA can be detected.
Given the complexity and high degree of particularity of this type of assay, we describe a detailed video protocol to study endonucleolytic cleavage by the cleavage/Poly(A) machinery of mRNA precursors in vitro. We describe how to prepare competent nuclear extracts, generate radiolabeled RNA substrates, perform the cleavage reaction, and analyze and interpret the resulting products. Figure 1 shows an example of substrate RNAs encoding for the 3&#8217; end of HIV-1 pre-mRNAs to be used for a cleavage assay. The 3&#8216; end of the HIV RNA genome is composed of many important regulatory sequences such as the poly(A) site, a G+U rich region, and the USE element, which are all necessary for efficient maturation of the viral mRNA transcripts13. In this example we would expect the input RNA substrate to be 338 nt and upon cleavage 237 nt. If polyadenylation was allowed to occur, a smear of products would be observed between 237 and 437 nt.

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			<td style="width:119px;">BP13354</td>
			<td></td>
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		<tr height="42">
			<td height="42" style="height:42px;width:216px;">10x TBE</td>
			<td style="width:141px;">Ameresco Life Sciences</td>
			<td style="width:119px;">0658-4L</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">10x PBS</td>
			<td style="width:141px;">Fisher</td>
			<td style="width:119px;">BP399-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Urea</td>
			<td style="width:141px;">Fisher</td>
			<td style="width:119px;">BP169-212</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ammonium Persulfate</td>
			<td style="width:141px;">Bio-Rad</td>
			<td style="width:119px;">161-0700</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:216px;">TEMED</td>
			<td style="width:141px;">Fisher</td>
			<td style="width:119px;">BP150-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Ammonium Acetate</td>
			<td style="width:141px;">Fisher</td>
			<td style="width:119px;">A637-500</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">40% 19:1 Acrylamide:Bis-acrylamide</td>
			<td style="width:141px;">Bio-Rad</td>
			<td style="width:119px;">161-0144</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Glycogen</td>
			<td style="width:141px;">Roche</td>
			<td style="width:119px;">10 901 393 001</td>
			<td></td>
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		<tr height="42">
			<td height="42" style="height:42px;width:216px;">100% Absolute Ethanol 200 Proof</td>
			<td style="width:141px;">Acros</td>
			<td style="width:119px;">61509-0040</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Acid Phenol-Chloroform</td>
			<td style="width:141px;">Ambion</td>
			<td style="width:119px;">9720</td>
			<td>For RNA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Scintilation Fluid</td>
			<td style="width:141px;">Fisher</td>
			<td style="width:119px;">SX18-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Rnase Inhibitor</td>
			<td style="width:141px;">Promega</td>
			<td style="width:119px;">N261B</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Poly (Vinyl alcohol) PVA</td>
			<td style="width:141px;">Sigma-Aldrich</td>
			<td style="width:119px;">P8136-250G</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Creatine Phosphate</td>
			<td style="width:141px;">Calbiochem</td>
			<td style="width:119px;">2380</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">100mM dATP</td>
			<td style="width:141px;">Fisher</td>
			<td style="width:119px;">BP2560-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">SDS</td>
			<td style="width:141px;">Acros</td>
			<td style="width:119px;">23042-5000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Proteinase K</td>
			<td style="width:141px;">Fisher</td>
			<td style="width:119px;">BP1700-100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Adjustable Sequencing Unit</td>
			<td style="width:141px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z351881-1EA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Binder Clips</td>
			<td style="width:141px;">Office Depot</td>
			<td style="width:119px;">838-056</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">20cmx42cm glass plates</td>
			<td style="width:141px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z352543</td>
			<td>1SET</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">20cmx22cm glass plates</td>
			<td style="width:141px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z35252-7</td>
			<td>1SET</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">20cmx42cm Aluminum Cooling Plates</td>
			<td style="width:141px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z352667</td>
			<td>1EA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">0.4mmx22cm Spacers</td>
			<td style="width:141px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z35230-6</td>
			<td>1SET</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">0.4mmx42cm Spacers</td>
			<td style="width:141px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z352314-1</td>
			<td>1SET</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">8-well Comb</td>
			<td style="width:141px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z35195-4</td>
			<td>1EA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">16-well Comb</td>
			<td style="width:141px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z351962</td>
			<td>1EA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">32-well Comb</td>
			<td style="width:141px;">Sigma-Aldrich</td>
			<td style="width:119px;">Z351970</td>
			<td>1EA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Gel Repel Coating</td>
			<td style="width:141px;">C.B.S. Scientific</td>
			<td style="width:119px;">SGR-0401</td>
			<td>or SGR-0101 for individual bottle</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Gel Loading Tips</td>
			<td style="width:141px;">Rainin</td>
			<td style="width:119px;">GT-10-4</td>
			<td>0.1-10uL</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Sequencing PowerPac HV</td>
			<td style="width:141px;">Bio-Rad</td>
			<td style="width:119px;">PowerPac HV</td>
			<td>5000V/500mA/400W</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Gel Dryer Model 583</td>
			<td style="width:141px;">Bio-Rad</td>
			<td style="width:119px;">Model 583</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Hydrotech Vacuum Pump for gel dryer</td>
			<td style="width:141px;">Bio-Rad</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">Glogos II Glow-in-the-dark Markers</td>
			<td style="width:141px;">Agilent</td>
			<td style="width:119px;">420201</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Film 8x10</td>
			<td style="width:141px;">Midsci</td>
			<td style="width:119px;">BX810</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Film 14x17</td>
			<td style="width:141px;">Phenix</td>
			<td style="width:119px;">F-BX1417</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Autoradiography Cassette</td>
			<td style="width:141px;">Fisher</td>
			<td style="width:119px;">FBCA 1417</td>
			<td>8x10 size available</td>
		</tr>
	</tbody>
</table>

analysis of rna processing reactions using cell free systems: 3' end cleavage of pre-mrna substrates in vitro

The 3&#8217; end of mammalian mRNAs is not formed by abrupt termination of transcription by RNA polymerase II (RNPII). Instead, RNPII synthesizes precursor mRNA beyond the end of mature RNAs, and an active process of endonuclease activity is required at a specific site. Cleavage of the precursor RNA normally occurs 10-30 nt downstream from the consensus polyA site (AAUAAA) after the CA dinucleotides. Proteins from the cleavage complex, a multifactorial protein complex of approximately 800 kDa, accomplish this specific nuclease activity. Specific RNA sequences upstream and downstream of the polyA site control the recruitment of the cleavage complex. Immediately after cleavage, pre-mRNAs are polyadenylated by the polyA polymerase (PAP) to produce mature stable RNA messages.
Processing of the 3&#8217; end of an RNA transcript may be studied using cellular nuclear extracts with specific radiolabeled RNA substrates. In sum, a long 32P-labeled uncleaved precursor RNA is incubated with nuclear extracts in vitro, and cleavage is assessed by gel electrophoresis and autoradiography. When proper cleavage occurs, a shorter 5&#8217; cleaved product is detected and quantified. Here, we describe the cleavage assay in detail using, as an example, the 3&#8217; end processing of HIV-1 mRNAs.

Representative results of a cleavage assay of the RNA poly(A) sites of HIV-1 (Figure 2). We can observe the uncleaved RNA substrate, which is the slowest migrating band at the top of the gel. The specific cleaved product is the most intense shorter fragment band that runs faster in the gel at the expected size, and is specifically absent from the cleavage assay of the mutpoly(A) control that contains a point mutation in the polyA sequence (mutPolyA) RNA substrate. Degradation products of the input substr...

Watch this Scientific Journal Video about Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro at JoVE.com

Analysis of RNA Processing Reactions Using Cell Free Systems: 3&#039; End Cleavage of Pre-mRNA Substrates in vitro

RNA polymerase II synthesizes a precursor RNA that extends beyond the 3' end of the mature mRNA. The end of the mature RNA is generated cotranscriptionally, at a site dictated by RNA sequences, via the endonuclease activity of the cleavage complex. Here, we detail the method to study cleavage reactions in vitro.

Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro

The 3&#8217; end of mammalian mRNAs is not formed by abrupt termination of transcription by RNA polymerase II (RNPII). Instead, RNPII synthesizes ...

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12.7K Views.  The Scripps Research Institute. RNA polymerase II synthesizes a precursor RNA that extends beyond the 3' end of the mature mRNA. The end of the mature RNA is generated cotranscriptionally, at a site dictated by RNA sequences, via the endonuclease activity of the cleavage complex. Here, we detail the method to study cleavage reactions in vitro.