Biochemistry Centre, Heidelberg University, 69120 Heidelberg, Germany.
Biochemistry Centre, Heidelberg University, 69120 Heidelberg, Germany
Proc Natl Acad Sci U S A. 2022 Mar 1;119(9). doi: 10.1073/pnas.2118286119.
Circadian clocks are timing systems that rhythmically adjust physiology and metabolism to the 24-h day-night cycle. Eukaryotic circadian clocks are based on transcriptional-translational feedback loops (TTFLs). Yet TTFL-core components such as Frequency (FRQ) in and Periods (PERs) in animals are not conserved, leaving unclear how a 24-h period is measured on the molecular level. Here, we show that CK1 is sufficient to promote FRQ and mouse PER2 (mPER2) hyperphosphorylation on a circadian timescale by targeting a large number of low-affinity phosphorylation sites. Slow phosphorylation kinetics rely on site-specific recruitment of Casein Kinase 1 (CK1) and access of intrinsically disordered segments of FRQ or mPER2 to bound CK1 and on CK1 autoinhibition. Compromising CK1 activity and substrate binding affects the circadian clock in and mammalian cells, respectively. We propose that CK1 and the clock proteins FRQ and PERs form functionally equivalent, phospho-based timing modules in the core of the circadian clocks of fungi and animals.
生物钟是一种计时系统，它使生理和代谢活动周期性地适应 24 小时的昼夜节律。真核生物钟基于转录-翻译反馈环（TTFL）。然而，TTFL 核心成分，如 中的频率（FRQ）和动物中的周期（PERs）并不保守，这使得分子水平上如何测量 24 小时周期仍不清楚。在这里，我们表明，通过靶向大量低亲和力磷酸化位点，蛋白激酶 CK1（CK1）足以在生物钟时间尺度上促进 FRQ 和小鼠 PER2（mPER2）的过度磷酸化。缓慢的磷酸化动力学依赖于 CK1 的特异性募集以及 FRQ 或 mPER2 的固有无序片段与结合的 CK1 以及 CK1 自身抑制的结合。CK1 活性和底物结合的受损分别影响 和哺乳动物细胞中的生物钟。我们提出，蛋白激酶 CK1 和时钟蛋白 FRQ 和 PERs 在真菌和动物生物钟的核心中形成功能等效的、基于磷酸化的计时模块。
