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pubmed:abstractText |
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.
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