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Mol. Cell. Biol., 10 1996, 5433-5443, Vol 16, No. 10
B Li, JA Weber, Y Chen, AL Greenleaf and DS Gilmour
Analyses of Drosophila cells have revealed that RNA polymerase II is paused
in a region 20 to 40 nucleotides downstream from the transcription start
site of the hsp70 heat shock gene when the gene is not transcriptionally
active. We have developed a cell-free system that reconstitutes this
promoter-proximal pausing. The paused polymerase has been detected by
monitoring the hyperreactivity of thymines in the transcription bubble
toward potassium permanganate. The pattern of permanganate reactivity for
the hsp70 promoter in the reconstituted system matches the pattern found on
the promoter after it has been introduced back into files by
P-element-mediated transposition. Matching patterns of permanganate
reactivity are also observed for a non-heat shock promoter, the histone H3
promoter. Further analysis of the hsp70 promoter in the reconstituted
system reveals that pausing does not depend on sequence-specific
interactions located immediately downstream from the pause site. Sequences
upstream from the TATA box influence the recruitment of polymerase rather
than the efficiency of pausing. Kinetic analysis indicates that the
polymerase rapidly enters the paused state and remains stably in this state
for at least 25 min. Further analysis shows that the paused polymerase will
initially resume elongation when Sarkosyl is added but loses this capacity
within minutes of pausing. Using an alpha-amanitin-resistant polymerase, we
provide evidence that promoter-proximal pausing does not require the
carboxy-terminal domain of the polymerase.
Copyright © 1996, American Society for Microbiology
Analyses of promoter-proximal pausing by RNA polymerase II on the hsp70 heat shock gene promoter in a Drosophila nuclear extract
Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park 16802, USA.
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