Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7260.
Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, NC 27599-7260
Proc Natl Acad Sci U S A. 2021 Jan 12;118(2). doi: 10.1073/pnas.2021174118. Epub 2020 Dec 21.
The mammalian circadian clock consists of a transcription-translation feedback loop (TTFL) composed of CLOCK-BMAL1 transcriptional activators and CRY-PER transcriptional repressors. Previous work showed that CRY inhibits CLOCK-BMAL1-activated transcription by a "blocking"-type mechanism and that CRY-PER inhibits CLOCK-BMAL1 by a "displacement"-type mechanism. While the mechanism of CRY-mediated repression was explained by both in vitro and in vivo experiments, the CRY-PER-mediated repression in vivo seemed in conflict with the in vitro data demonstrating PER removes CRY from the CLOCK-BMAL1-E-box complex. Here, we show that CRY-PER participates in the displacement-type repression by recruiting CK1δ to the nucleus and mediating an increased local concentration of CK1δ at CLOCK-BMAL1-bound promoters/enhancers and thus promoting the phosphorylation of CLOCK and dissociation of CLOCK-BMAL1 along with CRY from the E-box. Our findings bring clarity to the role of PER in the dynamic nature of the repressive phase of the TTFL.
哺乳动物的生物钟由一个转录-翻译反馈环（TTFL）组成，该反馈环由 CLOCK-BMAL1 转录激活因子和 CRY-PER 转录抑制因子组成。以前的工作表明，CRY 通过“阻断”型机制抑制 CLOCK-BMAL1 激活的转录，而 CRY-PER 通过“置换”型机制抑制 CLOCK-BMAL1。虽然体外和体内实验都解释了 CRY 介导的抑制机制，但 CRY-PER 在体内的抑制作用与体外数据似乎相矛盾，体外数据表明 PER 将 CRY 从 CLOCK-BMAL1-E 盒复合物中移除。在这里，我们表明 CRY-PER 通过将 CK1δ 招募到细胞核中并介导 CK1δ 在 CLOCK-BMAL1 结合的启动子/增强子处的局部浓度增加，从而促进 CLOCK 的磷酸化以及 CLOCK-BMAL1 与 CRY 从 E 盒解离，从而参与置换型抑制。我们的发现阐明了 PER 在 TTFL 的抑制相的动态性质中的作用。
