DOUBLETIME Plays a Noncatalytic Role To Mediate CLOCK Phosphorylation and Repress CLOCK-Dependent Transcription within the Drosophila Circadian Clock
DOUBLETIME Plays a Noncatalytic Role To Mediate CLOCK Phosphorylation and Repress CLOCK-Dependent Transcription within the Drosophila Circadian Clock
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DOI：
10.1128/mcb.01777-08
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发表时间：
2009-03-15
影响因子：
5.3
通讯作者：
Hardin, Paul E.
中科院分区：
文献类型：
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作者：
Yu, Wangjie;Zheng, Hao;Hardin, Paul E.
生物钟通过基因表达反馈回路保持时间，该回路由转录因子合成、活性和降解中的特定时间变化控制。在果蝇的生物钟中，DOUBLETIME （DBT）激酶对于转录抑制因子PERIOD （PER）和转录激活因子clock （CLK）的磷酸化是必需的，因为CLK依赖性的转录被抑制。含有PER-和DBT的蛋白复合物反馈抑制CLK依赖性转录，但DBT如何促进PER和CLK磷酸化，以及PER和CLK磷酸化如何促进转录抑制尚未明确。在这里，我们表明DBT的催化活性不是CLK磷酸化或转录抑制所必需的，并且PER磷酸化对于抑制CLK依赖性转录是必不可少的。这些结果支持了DBT在募集磷酸化CLK的额外激酶中发挥新的非催化作用，从而抑制转录的模型。考虑到PER、DBT和CLK同源基因的保守活性，哺乳动物中可能也存在类似的机制。
Circadian clocks keep time via gene expression feedback loops that are controlled by time-of-day-specific changes in the synthesis, activity, and degradation of transcription factors. Within the Drosophila melanogaster circadian clock, DOUBLETIME (DBT) kinase is necessary for the phosphorylation of PERIOD (PER), a transcriptional repressor, and CLOCK (CLK), a transcriptional activator, as CLK-dependent transcription is being repressed. PER- and DBT-containing protein complexes feed back to repress CLK-dependent transcription, but how DBT promotes PER and CLK phosphorylation and how PER and CLK phosphorylation contributes to transcriptional repression have not been defined. Here, we show that DBT catalytic activity is not required for CLK phosphorylation or transcriptional repression and that PER phosphorylation is dispensable for repressing CLK-dependent transcription. These results support a model in which DBT plays a novel noncatalytic role in recruiting additional kinases that phosphorylate CLK, thereby repressing transcription. A similar mechanism likely operates in mammals, given the conserved activities of PER, DBT, and CLK orthologs.