Evidence for an overlapping role of CLOCK and NPAS2 transcription factors in liver circadian oscillators
Evidence for an overlapping role of CLOCK and NPAS2 transcription factors in liver circadian oscillators
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DOI：
10.1128/mcb.01931-07
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发表时间：
2008-05-01
影响因子：
5.3
通讯作者：
Pinotti, Mirko
中科院分区：
文献类型：
--
作者：
Bertolucci, Cristiano;Cavallari, Nicola;Pinotti, Mirko
外周组织中基因表达的昼夜节律控制和影响许多生物学途径的机制尚不清楚。因子VII（FVII），触发血液凝固的蛋白酶，代表了解决肝脏中这个问题的有价值的模型，因为其血浆水平以昼夜节律方式振荡，并且其启动子含有E盒，其是CLOCK-BMAL 1和NPAS 2-BMAL 1异二聚体的推定DNA结合位点和昼夜节律调节的标志。野生型小鼠肝脏中FVII mRNA水平的峰值先于血浆中的峰值，表明转录调节，并且在Clock（-/-）; Npas 2（-/-）小鼠中被消除，从而证明了CLOCK和Npas 2昼夜节律转录因子的作用。对表达功能缺陷异二聚体的Npas 2（-/-）和Clock（Delta 19/Delta 19）小鼠的研究揭示了两种动物模型中FVII表达的稳健节律，表明NPAS 2和CLOCK的冗余作用。这些观察结果的分子基础是通过报告基因测定建立的。NPAS 2-BMAL 1和CLOCK-BMAL 1异源二聚体的FVII反式激活活性是（i）相当的（增加四倍），（ii）被负昼夜节律调节剂PER 2和PER 1抑制，和（iii）在E盒诱变后消除。我们的数据提供了第一个证据，外周振荡器的重叠作用的时钟和NPAS 2的调节昼夜节律控制的基因。
The mechanisms underlying the circadian control of gene expression in peripheral tissues and influencing many biological pathways are poorly defined. Factor VII (FVII), the protease triggering blood coagulation, represents a valuable model to address this issue in liver since its plasma levels oscillate in a circadian manner and its promoter contains E-boxes, which are putative DNA-binding sites for CLOCK-BMAL1 and NPAS2-BMAL1 heterodimers and hallmarks of circadian regulation. The peaks of FVII mRNA levels in livers of wild-type mice preceded those in plasma, indicating a transcriptional regulation, and were abolished in Clock(-/-); Npas2(-/-) mice, thus demonstrating a role for CLOCK and NPAS2 circadian transcription factors. The investigation of Npas2(-/-) and Clock(Delta 19/Delta 19) mice, which express functionally defective heterodimers, revealed robust rhythms of FVII expression in both animal models, suggesting a redundant role for NPAS2 and CLOCK. The molecular bases of these observations were established through reporter gene assays. FVII transactivation activities of the NPAS2-BMAL1 and CLOCK-BMAL1 heterodimers were (i) comparable (a fourfold increase), (ii) dampened by the negative circadian regulators PER2 and CRY1, and (iii) abolished upon E-box mutagenesis. Our data provide the first evidence in peripheral oscillators for an overlapping role of CLOCK and NPAS2 in the regulation of circadianly controlled genes.