Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202, USA.
J Biol Chem. 2011 Oct 28;286(43):37053-7. doi: 10.1074/jbc.C111.295915. Epub 2011 Sep 14.
Mediator complex functions at the recruitment as well as the post-recruitment steps of transcription. Here we provide evidence for a novel role of Mediator in termination of transcription. Mediator subunit Srb5/Med18 cross-links to the 5' and 3' ends of INO1 and CHA1. In srb5(-) cells, recruitment of TATA-binding protein (TBP) and transcription factor IIB (TFIIB) onto the promoter of these genes remained unaffected, but cross-linking of the cleavage-polyadenylation factors Rna15 and Pta1 toward the 3' end of genes was compromised. In these cells, RNA polymerase II accumulated near the 3' end of genes and beyond. Transcription run-on analysis confirmed a transcription readthrough phenotype in the absence of Srb5/Med18. These results strongly suggest that Mediator subunit Srb5/Med18 is required for proper termination of transcription of a subset of genes in budding yeast.
中介复合物在转录的招募以及招募后的步骤中发挥作用。在这里，我们提供了中介复合物在转录终止中发挥作用的新证据。中介亚基 Srb5/Med18 与 INO1 和 CHA1 的 5' 和 3' 末端交联。在 srb5(-) 细胞中，TATA 结合蛋白 (TBP) 和转录因子 IIB (TFIIB) 招募到这些基因的启动子上仍然不受影响，但 RNA 切割多聚腺苷酸化因子 Rna15 和 Pta1 向基因 3' 末端的交联受到损害。在这些细胞中，RNA 聚合酶 II 在基因 3' 末端附近和之外积累。转录运行分析证实了在没有 Srb5/Med18 的情况下转录通读表型。这些结果强烈表明，中介复合物亚基 Srb5/Med18 是芽殖酵母中一组基因正确转录终止所必需的。
