Awrey D E, Weilbaecher R G, Hemming S A, Orlicky S M, Kane C M, Edwards A M
Cancer Research Group, Institute for Molecular Biology and Biotechnology, McMaster University, Hamilton, Ontario L8N 3Z5, Canada.
J Biol Chem. 1997 Jun 6;272(23):14747-54. doi: 10.1074/jbc.272.23.14747.
The role of yeast RNA polymerase II (pol II) subunit RPB9 in transcript elongation was investigated by examining the biochemical properties of pol II lacking RPB9 (pol IIDelta9). The maximal rate of chain elongation was nearly identical for pol II and pol IIDelta9. By contrast, pol IIDelta9 elongated more efficiently through DNA sequences that signal the elongation complex to pause or arrest. The addition of purified recombinant RPB9 to pol IIDelta9 restored the elongation properties of the mutant polymerase to those of the wild-type enzyme. Arrested pol IIDelta9 complexes were refractory to levels of TFIIS that promoted maximal read-through with pol II. However, both pol II and pol IIDelta9 complexes stimulated with TFIIS undergo transcript cleavage, confirming that transcript cleavage and read-through activities can be uncoupled. Our observations suggest that both TFIIS and RPB9 are required to stimulate the release of RNA polymerase II from the arrested state.
通过检测缺乏RPB9的RNA聚合酶II（pol II）（pol IIDelta9）的生化特性，研究了酵母RNA聚合酶II亚基RPB9在转录延伸中的作用。pol II和pol IIDelta9的最大链延伸速率几乎相同。相比之下，pol IIDelta9通过那些使延伸复合物暂停或停滞的DNA序列时延伸效率更高。向pol IIDelta9中添加纯化的重组RPB9可使突变聚合酶的延伸特性恢复到野生型酶的水平。停滞的pol IIDelta9复合物对TFIIS的水平不敏感，而TFIIS能促进pol II的最大通读。然而，用TFIIS刺激的pol II和pol IIDelta9复合物都会发生转录切割，这证实了转录切割和通读活性可以解偶联。我们的观察结果表明，TFIIS和RPB9都是刺激RNA聚合酶II从停滞状态释放所必需的。
