The role of Rat1 in coupling mRNA 3'-end processing to transcription termination: implications for a unified allosteric-torpedo model.
The torpedo model of transcription termination by RNA polymerase II proposes that a 5'-3' RNA exonuclease enters at the poly(A) cleavage site, degrades the nascent RNA, and eventually displaces polymerase from the DNA. Cotranscriptional degradation of nascent RNA has not been directly demonstrated, however. Here we report that two exonucleases, Rat1 and Xrn1, both contribute to cotranscriptional degradation of nascent RNA, but this degradation is not sufficient to cause polymerase release. Unexpectedly, Rat1 functions in both 3'-end processing and termination by enhancing recruitment of 3'-end processing factors, including Pcf11 and Rna15. In addition, the cleavage factor Pcf11 reciprocally aids in recruitment of Rat1 to the elongation complex. Our results suggest a unified allosteric/torpedo model in which Rat1 is not a dedicated termination factor, but is an integrated component of the cleavage/polyadenylation apparatus.
Luo
Weifei
W
Department of Biochemistry and Molecular Genetics, University of Colorado School of Medicine, University of Colorado Health Sciences Center at Fitzsimons, Aurora, Colorado 80045, USA.
Johnson
Arlen W
AW
Bentley
David L
DL
D000494:Allosteric Regulation; D000818:Animals; D005095:Exoribonucleases / Q000378:metabolism; D006868:Hydrolysis; D008962:Models, Theoretical; D010957:Plasmids; D012323:RNA Processing, Post-Transcriptional; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D013728:Terminator Regions, Genetic; D014158:Transcription, Genetic
D012333:RNA, Messenger; D029701:Saccharomyces cerevisiae Proteins; D005095:Exoribonucleases; C068398:XRN1 protein, S cerevisiae