美国怀特黑德生物医学研究所Richard A. Young研究组取得进展。他们的研究发现Pol Ⅱ磷酸化调控转录和剪接复合物之间的转换。该研究成果发表在2019年8月22日出版的《自然》上。

课题组人员通过研究Pol Ⅱ C末端结构域的磷酸化，是否调节PolⅡ掺入与转录起始和剪接相关复合物的相分离，发现具有低磷酸化C末端的Pol Ⅱ与转录中介复合物结合，并且由细胞周期蛋白依赖性激酶磷酸化的Pol Ⅱ会减少了这种结合。研究人员还发现，过度磷酸化C末端结构域的Pol Ⅱ会优先进入由剪接因子形成的复合物中。结果表明，PolⅡ C末端结构域的磷酸化驱动从转录起始复合物到RNA加工复合物的转换，这暗示磷酸化作为调节Pol Ⅱ结合不同复合物偏好性的机制。

RNA聚合酶 Ⅱ（Pol  Ⅱ）合成前体mRNA包括转录起始复合物的形成到延伸复合物的转换。Pol Ⅱ的大亚基含有无序的C末端结构域，其在从起始到延伸的过渡期间被细胞周期蛋白依赖性激酶磷酸化，从而影响C末端结构域与起始复合物的不同组分或RNA-剪接体的相互作用。最近的研究表明，该模型仅揭示了C-末端结构域磷酸化部分的作用机制。转录起始复合物和剪接复合物都可以形成相分离的液滴，这些液滴含有大量的元件分子如：数百个Pol Ⅱ和mediator分子在超级增强子区形成相分离液滴，大量的剪接因子集中在核斑点区，其中一些出现在高度活跃的转录位点。

附：英文原文

Title: Pol II phosphorylation regulates a switch between transcriptional and splicing condensates

Author: Yang Eric Guo, John C. Manteiga, Jonathan E. Henninger, Benjamin R. Sabari, Alessandra Dall’Agnese, Nancy M. Hannett, Jan-Hendrik Spille, Lena K. Afeyan, Alicia V. Zamudio, Krishna Shrinivas, Brian J. Abraham, Ann Boija, Tim-Michael Decker, Jenna K. Rimel, Charli B. Fant, Tong Ihn Lee, Ibrahim I. Cisse, Phillip A. Sharp, Dylan J. Taatjes, Richard A. Young

Issue&Volume:Volume 572 Issue 7770

Abstract: 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. 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. Recent observations suggest that this model provides only a partial picture of the effects of phosphorylation of the C-terminal domain. 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, and large numbers of splicing factors are concentrated in nuclear speckles, some of which occur at highly active transcription sites. 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.

DOI: 10.1038/s41586-019-1464-0

Source:https://www.nature.com/articles/s41586-019-1464-0