Architecture of initiation-competent 12-subunit RNA polymerase II
Architecture of initiation-competent 12-subunit RNA polymerase II
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DOI：
10.1073/pnas.1030608100
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发表时间：
2003-06-10
影响因子：
11.1
通讯作者：
Cramer, P
中科院分区：
文献类型：
--
作者：
Armache, KJ;Kettenberger, H;Cramer, P
RNA 聚合酶 (Pol) II 由 10 多肽催化核心和转录起始所需的两个亚基 Rpb4/7 复合物组成。 Pol II 核心的先前结构揭示了一个“夹子”，它通过三个“开关区域”结合 DNA 模板链，以及一个与 C 端重复结构域 (CTD) 相连的灵活“接头”。在这里，我们通过将核心和 Rpb4/7 的结构拟合到 4.2 埃晶体电子密度图，得出了完整 Pol II 的模型。 Rpb4/7 从聚合酶“上游面”突出，在其上组装启动因子以加载启动子 DNA。 Rpb7 在夹具和连接器之间形成楔子，将夹具限制在关闭位置。楔形变构阻止启动子 DNA 双链体进入活性中心裂口，并在两个开关区域诱导模板链结合的构象。 Rpb4/7 与接头的相互作用解释了在 Pol II 回收过程中 Rpb4 介导的 CTD 磷酸酶向 CTD 的募集。核心-Rpb7 相互作用和 Rpb4/7 的一些功能显然在所有真核和古细菌 RNA 聚合酶中都是保守的，但在细菌酶中则不然。
RNA polymerase (Pol) II consists of a 10-polypeptide catalytic core and the two-subunit Rpb4/7 complex that is required for transcription initiation. Previous structures of the Pol II core revealed a "clamp," which binds the DNA template strand via three "switch regions," and a flexible "linker" to the C-terminal repeat domain (CTD). Here we derived a model of the complete Pol II by fitting structures of the core and Rpb4/7 to a 4.2-Angstrom crystallographic electron density map. Rpb4/7 protrudes from the polymerase "upstream face," on which initiation factors assemble for promoter DNA loading. Rpb7 forms a wedge between the clamp and the linker, restricting the clamp to a closed position. The wedge allosterically prevents entry of the promoter DNA duplex into the active center cleft and induces in two switch regions a conformation poised for template-strand binding. Interaction of Rpb4/7 with the linker explains Rpb4-mediated recruitment of the CTD phosphatase to the CTD during Pol II recycling. The core-Rpb7 interaction and some functions of Rpb4/7 are apparently conserved in all eukaryotic and archaeal RNA polymerases but not in the bacterial enzyme.