Post-translational regulation of circadian transcriptional CLOCK(NPAS2)/BMAL1 complex by CRYPTOCHROMES
Post-translational regulation of circadian transcriptional CLOCK(NPAS2)/BMAL1 complex by CRYPTOCHROMES
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DOI：
10.4161/cc.5.8.2684
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发表时间：
2006-04-15
期刊：
影响因子：
4.3
通讯作者：
Antoch, Marina P.
中科院分区：
文献类型：
--
作者：
Kondratov, Roman V.;Kondratova, Anna A.;Antoch, Marina P.
哺乳动物的时钟（NPAS2），BMAL1和线粒体色素是昼夜节律振荡机制的核心组成部分。活性CLOCK/BMAL1或NPAS2/BMAL1复合物调节许多基因的表达，包括两个隐花色素。这些基因的产物，CLOCK 1和CLOCK 2，反过来又通过一种未知的机制抑制CLOCK/BMAL1的转录活性。我们已经研究了内源性和异位表达的CLOCK（NPAS2）和BMAL1蛋白的翻译后修饰和细胞内分布的影响。我们发现，异位共表达与CRY导致稳定和核积累的非磷酸化形式的蛋白质，这直接相关的抑制其转录活性。这种效应是CRY特异性的，因为CLOCK/BMAL1和NPAS2/BMAL1转录活性的其他已知阻遏物不能诱导类似的效应。β对CLOCK（NPAS2）/BMAL1复合物的形成或其结合DNA的能力没有影响。总之，这些结果表明，转录因子在翻译后水平调节昼夜转录复合物的功能活性。重要的是，CLOCK和BMAL1蛋白的翻译后修饰和细胞内分布在Cry基因靶向破坏的小鼠组织中严重受损，从而证实了CRY在体内时钟功能中的作用。基于这些发现，我们提出了一个修改的昼夜转录控制模型，这意味着CRY介导的周期性旋转的转录活性和非活性形式的CLOCK/BMAL1的启动子。该模型为先前报道的CLOCK/BMAL1双功能活性提供了机制解释，并强调了昼夜节律系统参与调节生物体对各种类型的遗传毒性应激（包括化疗和放疗）的反应。
Mammalian CLOCK( NPAS2), BMAL1 and CRYPTOCHROMEs are core components of the circadian oscillatory mechanism. The active CLOCK/ BMAL1 or NPAS2/ BMAL1 complexes regulate expression of numerous genes including two Cryptochromes. The products of these genes, CRY1 and CRY2, in turn repress CLOCK/ BMAL1 transcriptional activity by an unknown mechanism. We have examined the effect of CRYPTOCHROMEs on posttranslational modifications and intracellular distribution of endogenous and ectopically expressed CLOCK( NPAS2) and BMAL1 proteins. We found that ectopic coexpression with CRY led to stabilization and nuclear accumulation of unphosphorylated forms of the proteins, which directly correlated with the inhibition of their transcriptional activity. This effect was CRY- specific, as other known repressors of CLOCK/ BMAL1 and NPAS2/ BMAL1 transcriptional activity were not able to induce similar effects. CRYs had no effect on CLOCK( NPAS2)/ BMAL1 complex formation or its ability to bind DNA. Altogether, these results demonstrate that CRYs regulate the functional activity of circadian transcriptional complex at the posttranslational level. Importantly, the posttranslational modifications and intracellular distribution of CLOCK and BMAL1 proteins were critically impaired in the tissues of mice with targeted disruption of both Cry genes, thus confirming the suggested role of CRY in clock function in vivo. Based on these findings we propose a modified model of the circadian transcriptional control, which implies CRY- mediated periodic rotation of transcriptionally active and inactive forms of CLOCK/ BMAL1 on the promoter. This model provides mechanistic explanation for previously reported dual functional activity of CLOCK/ BMAL1 and highlights the involvement of the circadian system in modulating the organism's response to various types of genotoxic stress, including chemotherapy and radiation.