Koyama Hiroshi, Ito Takahiro, Nakanishi Toshiyuki, Sekimizu Kazuhisa
Department of Microbiology, Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Genes Cells. 2007 May;12(5):547-59. doi: 10.1111/j.1365-2443.2007.01072.x.
The transcription elongation factor S-II, also designated TFIIS, stimulates the nascent transcript cleavage activity intrinsic to RNA polymerase II. Rpb9, a small subunit of RNA polymerase II, enhances the cleavage stimulation activity of S-II. Here, we investigated the role of nascent transcript cleavage stimulation activity on the maintenance of transcriptional fidelity in yeast. In yeast, S-II is encoded by the DST1 gene. Disruption of the DST1 gene decreased transcriptional fidelity in cells. Mutations in the DST1 gene that reduce the S-II cleavage stimulation activity led to decreased transcriptional fidelity in cells. A disruption mutant of the RPB9 gene also had decreased transcriptional fidelity. Expression of mutant Rpb9 proteins that are unable to enhance the S-II cleavage stimulation activity failed to restore the phenotype. These results suggest that both S-II and Rpb9 maintain transcriptional fidelity by stimulating the cleavage activity intrinsic to RNA polymerase II. Also, a DST1 and RPB9 double mutant had more severe transcriptional fidelity defect compared with the DST1 gene deletion mutant, suggesting that Rpb9 maintains transcriptional fidelity via two mechanisms, enhancement of S-II dependent cleavage stimulation and S-II independent function(s).
转录延伸因子S-II，也称为TFIIS，可刺激RNA聚合酶II固有的新生转录本切割活性。RNA聚合酶II的小亚基Rpb9可增强S-II的切割刺激活性。在此，我们研究了新生转录本切割刺激活性在酵母转录保真度维持中的作用。在酵母中，S-II由DST1基因编码。DST1基因的破坏降低了细胞中的转录保真度。DST1基因中降低S-II切割刺激活性的突变导致细胞中的转录保真度降低。RPB9基因的破坏突变体的转录保真度也降低。无法增强S-II切割刺激活性的突变Rpb9蛋白的表达未能恢复该表型。这些结果表明，S-II和Rpb9均通过刺激RNA聚合酶II固有的切割活性来维持转录保真度。此外，与DST1基因缺失突变体相比，DST1和RPB9双突变体具有更严重的转录保真度缺陷，这表明Rpb9通过两种机制维持转录保真度，即增强S-II依赖性切割刺激和S-II非依赖性功能。
