Transcriptional pausing, arrest, and readthrough at the adenovirus major late attenuation site.
RNA polymerase II (pol II) transcription complexes initiated from the adenovirus major late promoter can become blocked both in vitro and in vivo at a specific site within the first intron of the transcription unit. In vitro, polymerases that fail to read through the major late attenuation site remain stably bound to the template in a ternary complex that is indefinitely blocked from continuing elongation, a phenomenon referred to as "arrest." Elongation factor SII has been shown both to promote readthrough of this and other arrest sites and to stimulate a previously unknown 3' to 5' exonuclease activity of pol II. We have proposed that the two activities are related and that SII promotes readthrough by means of the enhancement of the exonuclease activity. In the experiments reported here, we have tested several features of that model. In particular, we have examined the hypothesis that SII stimulates readthrough by allowing the polymerase to undergo multiple cycles of removal and resynthesis of RNA bases preceding the attenuation site. In addition, we present experimental support for the proposal that the length of time polymerase pauses at the attenuation site is important to the efficiency of arrest. The results of these experiments are discussed in the context of the model.
Hawley
D K
DK
Institute of Molecular Biology, University of Oregon, Eugene 97403.
Wiest
D K
DK
Holtz
M S
MS
Wang
D
D
D000256:Adenoviridae / Q000235:genetics*; D001483:Base Sequence; D005092:Exonucleases / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000235:genetics; D006801:Humans; D008957:Models, Genetic; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012319:RNA Polymerase II / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D014157:Transcription Factors / Q000378:metabolism*; D035165:Transcription Factors, General; D014158:Transcription, Genetic; D035602:Transcriptional Elongation Factors
D012333:RNA, Messenger; D014157:Transcription Factors; D035165:Transcription Factors, General; D035602:Transcriptional Elongation Factors; C018648:transcription factor S-II; D012319:RNA Polymerase II; D005092:Exonucleases