NASCENT RNA CLEAVAGE BY ARRESTED RNA POLYMERASE-II DOES NOT REQUIRE UPSTREAM TRANSLOCATION OF THE ELONGATION COMPLEX ON DNA

Citation
Wg. Gu et al., NASCENT RNA CLEAVAGE BY ARRESTED RNA POLYMERASE-II DOES NOT REQUIRE UPSTREAM TRANSLOCATION OF THE ELONGATION COMPLEX ON DNA, The Journal of biological chemistry, 268(34), 1993, pp. 25604-25616
Citations number
49
Categorie Soggetti
Biology
ISSN journal
00219258
Volume
268
Issue
34
Year of publication
1993
Pages
25604 - 25616
Database
ISI
SICI code
0021-9258(1993)268:34<25604:NRCBAR>2.0.ZU;2-E
Abstract
Obstacles incurred by RNA polymerase II during primary transcript synt hesis have been identified in vivo and in vitro. Transcription past th ese impediments requires SII, an RNA polymerase II-binding protein. SI I also activates a nuclease in arrested elongation complexes and this nascent RNA shortening precedes transcriptional readthrough. Here we s how that in the presence of SII and nucleotides, transcript cleavage i s detected during SII-dependent elongation but not during SII-independ ent transcription. Thus, under typical transcription conditions, SII i s necessary but insufficient to activate RNA cleavage. RNA cleavage co uld serve to move RNA polymerase II away from the transcriptional impe diment and/or permit RNA polymerase II multiple attempts at RNA elonga tion. By mapping the positions of the 3'-ends of RNAs and the elongati on complex on DNA, we demonstrate that upstream movement of RNA polyme rase II is not required for limited RNA shortening (seven to nine nucl eotides) and reactivation of an arrested complex. Arrested complexes b ecome elongation competent after removal of no more than nine nucleoti des from the nascent RNA's 3'-end. Further cleavage of nascent RNA, ho wever, does result in ''backward'' translocation of the enzyme. We als o show that one round of RNA cleavage is insufficient for full readthr ough at an arrest site, consistent with a previously suggested mechani sm of SII action.