Schilbach S, Hantsche M, Tegunov D, Dienemann C, Wigge C, Urlaub H, Cramer P
Max Planck Institute for Biophysical Chemistry, Department of Molecular Biology, Am Fassberg 11, 37077 Göttingen, Germany.
University Medical Center Göttingen, Institute of Clinical Chemistry, Bioanalytics Group, Robert-Koch-Straße 40, 37075 Göttingen, Germany.
Nature. 2017 Nov 9;551(7679):204-209. doi: 10.1038/nature24282. Epub 2017 Nov 1.
For the initiation of transcription, RNA polymerase II (Pol II) assembles with general transcription factors on promoter DNA to form the pre-initiation complex (PIC). Here we report cryo-electron microscopy structures of the Saccharomyces cerevisiae PIC and PIC-core Mediator complex at nominal resolutions of 4.7 Å and 5.8 Å, respectively. The structures reveal transcription factor IIH (TFIIH), and suggest how the core and kinase TFIIH modules function in the opening of promoter DNA and the phosphorylation of Pol II, respectively. The TFIIH core subunit Ssl2 (a homologue of human XPB) is positioned on downstream DNA by the 'E-bridge' helix in TFIIE, consistent with TFIIE-stimulated DNA opening. The TFIIH kinase module subunit Tfb3 (MAT1 in human) anchors the kinase Kin28 (CDK7), which is mobile in the PIC but preferentially located between the Mediator hook and shoulder in the PIC-core Mediator complex. Open spaces between the Mediator head and middle modules may allow access of the kinase to its substrate, the C-terminal domain of Pol II.
为了启动转录，RNA聚合酶II（Pol II）与通用转录因子在启动子DNA上组装，形成预启动复合物（PIC）。在此，我们分别报道了酿酒酵母PIC和PIC-核心中介体复合物的冷冻电子显微镜结构，标称分辨率分别为4.7 Å和5.8 Å。这些结构揭示了转录因子IIH（TFIIH），并表明核心和激酶TFIIH模块分别在启动子DNA的打开和Pol II的磷酸化过程中如何发挥作用。TFIIH核心亚基Ssl2（人类XPB的同源物）通过TFIIE中的“E桥”螺旋定位在下游DNA上，这与TFIIE刺激的DNA打开一致。TFIIH激酶模块亚基Tfb3（人类中的MAT1）锚定激酶Kin28（CDK7），后者在PIC中是可移动的，但在PIC-核心中介体复合物中优先位于中介体钩和肩部之间。中介体头部和中间模块之间的开放空间可能允许激酶接近其底物，即Pol II的C末端结构域。
