Polyadenylation releases mRNA from RNA polymerase II in a process that is licensed by splicing
- 1Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, California 90095-1569, USA
- 2Molecular Biology Institute, University of California at Los Angeles, Los Angeles, California 90095-1570, USA
Abstract
When transcription is coupled to pre-mRNA processing in HeLa nuclear extracts nascent transcripts become attached to RNA polymerase II during assembly of the cleavage/polyadenylation apparatus (CPA), and are not released even after cleavage at the poly(A) site. Here we show that these cleaved transcripts are anchored to the polymerase at their 3′ ends by the CPA or, when introns are present, by the larger 3′-terminal exon definition complex (EDC), which consists of splicing factors complexed with the CPA. Poly(A) addition releases the RNA from the polymerase when the RNA is anchored only by the CPA. When anchored by the EDC, poly(A) addition remains a requirement, but it triggers release only after being licensed by splicing. The process by which RNA must first be attached to the polymerase by the EDC, and then can only be released following dual inputs from splicing and polyadenylation, provides an obvious opportunity for surveillance as the RNA enters the transport pathway.
Keywords
- RNA processing
- cotranscriptional processing
- transcript release
- poly(A) signal
- cleavage and polyadenylation
- splicing
- exon definition complex
- coupling
Footnotes
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Reprint requests to: Harold G. Martinson, Department of Chemistry and Biochemistry, University of California at Los Angeles, 607 Charles E. Young Drive East, Box 951569, Los Angeles, CA 90095-1569, USA; e-mail: hgm{at}chem.ucla.edu; fax: (310) 206-4038.
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Article published online ahead of print. Article and publication date are at http://www.rnajournal.org/cgi/doi/10.1261/rna.1409209.
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- Received October 7, 2008.
- Accepted January 23, 2009.
- Copyright © 2009 RNA Society
