Hu Ping, Samudre Kalpana, Wu Si, Sun Yuling, Hernandez Nouria
Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
Mol Cell. 2004 Oct 8;16(1):81-92. doi: 10.1016/j.molcel.2004.09.008.
RNA polymerase III (pol III) transcription from the human U6 snRNA promoter can be reconstituted with the recombinant factors SNAPc and Brf2-TFIIIB combined with purified pol III. In this system, CK2 treatment of the pol III complex is required for transcription, whereas treatment of Brf2-TFIIIB is inhibitory. Here we show that CK2 inhibits Brf2-TFIIIB by specifically phosphorylating its Bdp1 component. Bdp1 is phosphorylated by CK2 during mitosis, and this is accompanied by Bdp1 dissociation from the U6 promoter and from chromatin in general and by transcription repression. Remarkably, whereas inhibition of CK2 in mitotic extracts restores pol III transcription, inhibition of CK2 in active S phase extracts debilitates transcription. Thus, CK2 is directed to phosphorylate different targets within the basal pol III transcription machinery at different times during the cell cycle, with opposite transcriptional effects.
人U6小核仁RNA（snRNA）启动子的RNA聚合酶III（pol III）转录可以通过重组因子小核RNA激活蛋白复合物（SNAPc）和Brf2 - TFIIIB与纯化的pol III组合来重建。在这个系统中，转录需要对pol III复合物进行CK2处理，而对Brf2 - TFIIIB的处理则具有抑制作用。在这里，我们表明CK2通过特异性磷酸化其Bdp1成分来抑制Brf2 - TFIIIB。在有丝分裂期间，Bdp1被CK2磷酸化，这伴随着Bdp1从U6启动子以及一般染色质上解离，并伴随着转录抑制。值得注意的是，虽然在有丝分裂提取物中抑制CK2可恢复pol III转录，但在活跃的S期提取物中抑制CK2会削弱转录。因此，在细胞周期的不同时间，CK2被导向磷酸化基础pol III转录机制内的不同靶点，产生相反的转录效应。
