PSEUDO-RESPONSE REGULATORS 9, 7, and 5 Are Transcriptional Repressors in the Arabidopsis Circadian Clock
PSEUDO-RESPONSE REGULATORS 9, 7, and 5 Are Transcriptional Repressors in the Arabidopsis Circadian Clock
复制标题
DOI：
10.1105/tpc.109.072892
复制
发表时间：
2010-03-01
期刊：
影响因子：
11.6
通讯作者：
Sakakibara, Hitoshi
中科院分区：
文献类型：
--
作者：
Nakamichi, Norihito;Kiba, Takatoshi;Sakakibara, Hitoshi
一个互锁的时钟相关基因转录-翻译反馈环被认为是植物生物钟的中心振荡器。CAB EXPRESSION1(也称为伪响应REGULATOR1[PRR1])的时序和两个MYB转录因子，即昼夜节律时钟ASSOCIATED1(CCA1)和晚期加长的下胚轴(LHY)在该环中起着关键作用。遗传学研究表明，PRR9、PRR7和PRR5也在环内或环附近发挥作用；然而，它们的分子功能仍不清楚。在这里，我们证明了PRR9、PRR7和PRR5作为CCA1和LHY的转录抑制因子。在瞬时报告实验中，PRR9、PRR7和PRR5分别抑制CCA1和LHY启动子的活性，并将转录抑制活性赋予异源DNA结合蛋白。利用糖皮质激素诱导的PRR5-GR(糖皮质激素受体)结构，我们发现PRR5直接下调CCA1和LHY的表达。此外，PRR9、PRR7和PRR5在体内与CCA1和LHY启动子结合，与CCA1和LHY表达下降的时间一致。这些结果表明，PRR9、PRR7和PRR5在CCA1和LHY启动子区域的抑制活性构成了这些蛋白质在生物钟反馈环中作用的分子机制。
An interlocking transcriptional-translational feedback loop of clock-associated genes is thought to be the central oscillator of the circadian clock in plants. TIMING OF CAB EXPRESSION1 (also called PSEUDO-RESPONSE REGULATOR1 [PRR1]) and two MYB transcription factors, CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY), play pivotal roles in the loop. Genetic studies have suggested that PRR9, PRR7, and PRR5 also act within or close to the loop; however, their molecular functions remain unknown. Here, we demonstrate that PRR9, PRR7, and PRR5 act as transcriptional repressors of CCA1 and LHY. PRR9, PRR7, and PRR5 each suppress CCA1 and LHY promoter activities and confer transcriptional repressor activity to a heterologous DNA binding protein in a transient reporter assay. Using a glucocorticoid-induced PRR5-GR (glucorticoid receptor) construct, we found that PRR5 directly downregulates CCA1 and LHY expression. Furthermore, PRR9, PRR7, and PRR5 associate with the CCA1 and LHY promoters in vivo, coincident with the timing of decreased CCA1 and LHY expression. These results suggest that the repressor activities of PRR9, PRR7, and PRR5 on the CCA1 and LHY promoter regions constitute the molecular mechanism that accounts for the role of these proteins in the feedback loop of the circadian clock.