Pol II phosphorylation regulates a switch between transcriptional and splicing condensates
Pol II phosphorylation regulates a switch between transcriptional and splicing condensates
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DOI：
10.1038/s41586-019-1464-0
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发表时间：
2019-08-22
期刊：
影响因子：
64.8
通讯作者：
Young, Richard A.
中科院分区：
文献类型：
--
作者：
Guo, Yang Eric;Manteiga, John C.;Young, Richard A.
RNA聚合酶II(POL II)合成Pre-mRNA包括转录起始复合体的形成和向延伸复合体(1-4)的过渡。POL II的大亚基含有一个内在无序的C-末端结构域，在从起始到延伸的转变过程中，该结构域被细胞周期蛋白依赖的蛋白激酶磷酸化，从而影响C-末端结构域与起始或RNA剪接装置的不同成分的相互作用(5，6)。最近的观察表明，这个模型只提供了C末端结构域(7-12)磷酸化影响的部分图像。转录启动机制和剪接机制都可以形成含有大量组分分子的相分离凝聚体：数百个POL II和介体分子集中在超级增强剂(7，8)的凝聚体中，大量剪接因子集中在核斑点中，其中一些出现在高活性的转录位点(9-12)。在这里，我们研究了POL II C-末端结构域的磷酸化是否调节了POL II在与转录启动和剪接相关的相分离的缩合物中的掺入。我们发现POL II的低磷酸化的C-末端结构域被结合到介体冷凝物中，并且调控的细胞周期蛋白依赖的激酶的磷酸化减少了这种结合。我们还发现，过度磷酸化的C-末端结构域优先结合到由剪接因子形成的缩合物中。这些结果表明，POL II C-末端结构域的磷酸化推动了参与转录启动的缩合物与参与RNA加工的缩合物之间的交换，并暗示了磷酸化是调节缩合物偏好的一种机制。
The synthesis of pre-mRNA by RNA polymerase II (Pol II) involves the formation of a transcription initiation complex, and a transition to an elongation complex(1-4). The large subunit of Pol II contains an intrinsically disordered C-terminal domain that is phosphorylated by cyclin-dependent kinases during the transition from initiation to elongation, thus influencing the interaction of the C-terminal domain with different components of the initiation or the RNA-splicing apparatus(5,6). Recent observations suggest that this model provides only a partial picture of the effects of phosphorylation of the C-terminal domain(7-12). Both the transcription-initiation machinery and the splicing machinery can form phase-separated condensates that contain large numbers of component molecules: hundreds of molecules of Pol II and mediator are concentrated in condensates at super-enhancers(7,8), and large numbers of splicing factors are concentrated in nuclear speckles, some of which occur at highly active transcription sites(9-12). Here we investigate whether the phosphorylation of the Pol II C-terminal domain regulates the incorporation of Pol II into phase-separated condensates that are associated with transcription initiation and splicing. We find that the hypophosphorylated C-terminal domain of Pol II is incorporated into mediator condensates and that phosphorylation by regulatory cyclin-dependent kinases reduces this incorporation. We also find that the hyperphosphorylated C-terminal domain is preferentially incorporated into condensates that are formed by splicing factors. These results suggest that phosphorylation of the Pol II C-terminal domain drives an exchange from condensates that are involved in transcription initiation to those that are involved in RNA processing, and implicates phosphorylation as a mechanism that regulates condensate preference.