Max Planck Institute for Biophysical Chemistry, Department of Molecular Biology, Am Fassberg 11, 37077 Göttingen, Germany.
Max Planck Institute for Biophysical Chemistry, Bioanalytical Mass Spectrometry, Am Fassberg 11, 37077 Göttingen, Germany; University Medical Center Göttingen, Institute of Clinical Chemistry, Bioanalytics Group, Robert-Koch-Straße 40, 37075 Göttingen, Germany.
Mol Cell. 2021 Aug 19;81(16):3386-3399.e10. doi: 10.1016/j.molcel.2021.06.019. Epub 2021 Jul 14.
The super elongation complex (SEC) contains the positive transcription elongation factor b (P-TEFb) and the subcomplex ELL2-EAF1, which stimulates RNA polymerase II (RNA Pol II) elongation. Here, we report the cryoelectron microscopy (cryo-EM) structure of ELL2-EAF1 bound to a RNA Pol II elongation complex at 2.8 Å resolution. The ELL2-EAF1 dimerization module directly binds the RNA Pol II lobe domain, explaining how SEC delivers P-TEFb to RNA Pol II. The same site on the lobe also binds the initiation factor TFIIF, consistent with SEC binding only after the transition from transcription initiation to elongation. Structure-guided functional analysis shows that the stimulation of RNA elongation requires the dimerization module and the ELL2 linker that tethers the module to the RNA Pol II protrusion. Our results show that SEC stimulates elongation allosterically and indicate that this stimulation involves stabilization of a closed conformation of the RNA Pol II active center cleft.
超级延伸复合物（SEC）包含正转录延伸因子 b（P-TEFb）和亚复合物 ELL2-EAF1，它们刺激 RNA 聚合酶 II（RNA Pol II）延伸。在这里，我们报告了 ELL2-EAF1 与 2.8 Å 分辨率的 RNA Pol II 延伸复合物结合的冷冻电镜（cryo-EM）结构。ELL2-EAF1 二聚化模块直接结合 RNA Pol II 叶状结构域，解释了 SEC 如何将 P-TEFb 递送到 RNA Pol II。叶状结构域上的同一位置也结合起始因子 TFIIF，这与 SEC 仅在从转录起始到延伸的转变之后结合一致。结构导向的功能分析表明，RNA 延伸的刺激需要二聚化模块和将模块连接到 RNA Pol II 突出物的 ELL2 接头。我们的结果表明，SEC 通过变构刺激延伸，并表明这种刺激涉及 RNA Pol II 活性中心裂隙的封闭构象的稳定。
