Department of Molecular Genetics, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, NE20, Cleveland, OH 44195, USA.
Proc Natl Acad Sci U S A. 2011 Sep 20;108(38):15786-91. doi: 10.1073/pnas.1104591108. Epub 2011 Sep 6.
Transcription factors TFIIB and TFIIF are both required for RNA polymerase II preinitiation complex (PIC) assembly, but their roles at and downstream of initiation are not clear. We now show that TFIIF phosphorylated by casein kinase 2 remains competent to support PIC assembly but is not stably retained in the PIC. PICs completely lacking TFIIF are not defective in initiation or subsequent promoter clearance, demonstrating that TFIIF is not required for initiation or clearance. Lack of TFIIF in the PIC reduces transcription levels at some promoters, coincident with reduced retention of TFIIB. TFIIB is normally associated with the early elongation complex and is only destabilized at +12 to +13. However, if TFIIF is not retained in the PIC, TFIIB can be lost immediately after initiation. TFIIF therefore has an important role in stabilizing TFIIB within the PIC and after transcription initiates.
转录因子 TFIIB 和 TFIIF 都需要 RNA 聚合酶 II 起始前复合物（PIC）的组装，但它们在起始和起始后的作用尚不清楚。我们现在表明，由酪蛋白激酶 2 磷酸化的 TFIIF 仍然有能力支持 PIC 组装，但不能稳定地保留在 PIC 中。完全缺乏 TFIIF 的 PIC 在起始或随后的启动子清除中没有缺陷，这表明 TFIIF 不是起始或清除所必需的。PIC 中 TFIIF 的缺失会降低一些启动子的转录水平，这与 TFIIB 的保留减少相一致。TFIIB 通常与早期延伸复合物相关联，并且仅在 +12 到 +13 处不稳定。然而，如果 PIC 中不保留 TFIIF，则 TFIIB 可以在起始后立即丢失。因此，TFIIF 在 PIC 内和转录起始后稳定 TFIIB 方面起着重要作用。
