Dynamics at the serine loop underlie differential affinity of cryptochromes for CLOCK:BMAL1 to control circadian timing
Dynamics at the serine loop underlie differential affinity of cryptochromes for CLOCK:BMAL1 to control circadian timing
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DOI：
10.7554/elife.55275
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发表时间：
2020-02-26
期刊：
影响因子：
7.7
通讯作者：
Partch, Carrie L.
中科院分区：
文献类型：
--
作者：
Fribourgh, Jennifer L.;Srivastava, Ashutosh;Partch, Carrie L.
哺乳动物的昼夜节律是由一个基于转录的反馈环产生的，其中CLOCK：BMAL 1驱动其阻遏物（PER 1/2，PER 1/2）的转录，这些阻遏物最终与CLOCK：BMAL 1相互作用，以类似于24小时的周期关闭反馈环。在这里，我们确定了一个关键的差异，在转录抑制因子的差异优势的基础上，EST 1和EST 2。这两种隐花色素结合BMAL 1反式激活结构域类似地将其从共激活因子中隔离并抑制CLOCK：BMAL 1活性。然而，我们发现，CLOCK：BMAL 1的PAS结构域核心以更高的亲和力被招募，使其能够作为一个更强的阻遏物，延长昼夜节律周期。我们发现了一个动态的富含丝氨酸的环邻近的二级口袋中的光裂合酶同源区（PHR）域，调节差异结合的隐花色素的PAS结构域核心的时钟：BMAL 1。值得注意的是，辅阻遏物PER 2的结合重塑了CRISPR 2的丝氨酸环，使其更像CRISPR 1，并增强了其对CLOCK：BMAL 1的亲和力。
Mammalian circadian rhythms are generated by a transcription-based feedback loop in which CLOCK:BMAL1 drives transcription of its repressors (PER1/2, CRY1/2), which ultimately interact with CLOCK:BMAL1 to close the feedback loop with similar to 24 hr periodicity. Here we pinpoint a key difference between CRY1 and CRY2 that underlies their differential strengths as transcriptional repressors. Both cryptochromes bind the BMAL1 transactivation domain similarly to sequester it from coactivators and repress CLOCK:BMAL1 activity. However, we find that CRY1 is recruited with much higher affinity to the PAS domain core of CLOCK:BMAL1, allowing it to serve as a stronger repressor that lengthens circadian period. We discovered a dynamic serine-rich loop adjacent to the secondary pocket in the photolyase homology region (PHR) domain that regulates differential binding of cryptochromes to the PAS domain core of CLOCK:BMAL1. Notably, binding of the co-repressor PER2 remodels the serine loop of CRY2, making it more CRY1-like and enhancing its affinity for CLOCK:BMAL1.