Douziech M, Coin F, Chipoulet J M, Arai Y, Ohkuma Y, Egly J M, Coulombe B
Département de Biologie, Faculté des Sciences, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada.
Mol Cell Biol. 2000 Nov;20(21):8168-77. doi: 10.1128/MCB.20.21.8168-8177.2000.
The p89/xeroderma pigmentosum complementation group B (XPB) ATPase-helicase of transcription factor IIH (TFIIH) is essential for promoter melting prior to transcription initiation by RNA polymerase II (RNAPII). By studying the topological organization of the initiation complex using site-specific protein-DNA photo-cross-linking, we have shown that p89/XPB makes promoter contacts both upstream and downstream of the initiation site. The upstream contact, which is in the region where promoter melting occurs (positions -9 to +2), requires tight DNA wrapping around RNAPII. The addition of hydrolyzable ATP tethers the template strand at positions -5 and +1 to RNAPII subunits. A mutation in p89/XPB found in a xeroderma pigmentosum patient impairs the ability of TFIIH to associate correctly with the complex and thereby melt promoter DNA. A model for open complex formation is proposed.
转录因子IIH（TFIIH）的p89/着色性干皮病互补组B（XPB）ATP酶解旋酶对于RNA聚合酶II（RNAPII）转录起始前的启动子解链至关重要。通过使用位点特异性蛋白质-DNA光交联研究起始复合物的拓扑结构，我们发现p89/XPB在起始位点的上游和下游均与启动子接触。上游接触位于启动子解链发生的区域（位置-9至+2），需要DNA紧密缠绕在RNAPII周围。可水解ATP的添加将模板链在位置-5和+1处与RNAPII亚基相连。在一名着色性干皮病患者中发现的p89/XPB突变损害了TFIIH与复合物正确结合并从而解链启动子DNA的能力。提出了开放复合物形成的模型。
