Functional Significance of FRH in Regulating the Phosphorylation and Stability of Neurospora Circadian Clock Protein FRQ
Functional Significance of FRH in Regulating the Phosphorylation and Stability of Neurospora Circadian Clock Protein FRQ
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DOI：
10.1074/jbc.m109.071688
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发表时间：
2010-04-09
影响因子：
4.8
通讯作者：
Liu, Yi
中科院分区：
文献类型：
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作者：
Guo, Jinhu;Cheng, Ping;Liu, Yi
频率(FRQ)是脉孢菌昼夜节律时钟的中心成分。所有FRQ蛋白都与FRH(FRQ相互作用RNA解旋酶)形成FFC复合体，FRH通过抑制FRQ的mRNA水平作为昼夜负反馈环中的负元件。为了了解FRQ-FRH相互作用的功能，我们定位并确定了FRQ-FRH相互作用所需的最小FRQ区域。我们证明了FRQ-FRH复合体的形成是FRQ与白领复合体(WCC)相互作用和时钟函数所必需的。另一方面，在FRQ-FRH复合体中，FRH-WCC相互作用也需要FRQ。FRQ-FRH相互作用的中断或FRH的下调会导致低磷酸化，FRQ的快速降解，以及白领-1和白领-2水平的降低。此外，我们还发现，在没有FRH的情况下，FRQ的快速降解不依赖于FWD-1，FWD-1是FRQ在正常条件下的泛素E3连接酶，从而揭示了FRQ降解的另一条途径。
FREQUENCY (FRQ) is the central component of the Neurospora circadian clock. All FRQ proteins form the FFC complex with FRH (FRQ-interacting RNA helicase) that acts as the negative element in the circadian negative feedback loop by repressing frq mRNA levels. To understand the function of the FRQ-FRH interaction, we mapped and identified the minimal FRQ region that is required for FRQ-FRH interaction. We demonstrated that the FRQ-FRH complex formation is required for the interaction between FRQ and the White Collar Complex (WCC) and clock function. On the other hand, in the FRQ-FRH complex, FRQ is also required for the FRH-WCC interaction. Disruption of FRQ-FRH interaction or down-regulation of FRH results in hypophosphorylation, rapid degradation of FRQ, as well as low levels of WHITE COLLAR-1 and WHITE COLLAR-2. Furthermore, we showed that the rapid FRQ degradation in the absence of FRH is independent of FWD-1, the ubiquitin E3 ligase of FRQ under normal conditions, thus uncovering an alternative pathway for FRQ degradation.