Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne NE2 4HH, UK.
Structure. 2012 Oct 10;20(10):1788-95. doi: 10.1016/j.str.2012.08.011. Epub 2012 Sep 6.
CDK9, the kinase of positive transcription elongation factor b (P-TEFb), stimulates transcription elongation by phosphorylating RNA polymerase II and transcription elongation factors. Using kinetic analysis of a human P-TEFb complex consisting of CDK9 and cyclin T, we show that the CDK9 C-terminal tail sequence is important for the catalytic mechanism and imposes an ordered binding of substrates and release of products. Crystallographic analysis of a CDK9/cyclin T complex in which the C-terminal tail partially blocks the ATP binding site reveals a possible reaction intermediate. Biochemical characterization of CDK9 mutants supports a model in which the CDK9 tail cycles through different conformational states. We propose that this mechanism is critical for the pattern of CTD Ser2 phosphorylation on actively transcribed genes.
CDK9，正转录延伸因子 b（P-TEFb）的激酶，通过磷酸化 RNA 聚合酶 II 和转录延伸因子来刺激转录延伸。通过对由 CDK9 和 cyclin T 组成的人 P-TEFb 复合物的动力学分析，我们表明 CDK9 C 端尾部序列对催化机制很重要，并对底物的结合和产物的释放施加了有序的影响。对部分阻断 ATP 结合位点的 CDK9/cyclin T 复合物的晶体结构分析揭示了一个可能的反应中间体。对 CDK9 突变体的生化特性的表征支持了这样一种模型，即 CDK9 尾部通过不同的构象状态循环。我们提出，这种机制对于活跃转录基因上 CTD Ser2 磷酸化的模式至关重要。
