Regulation of theNeurospora circadian clock by casein kinase II
Abstract
Phosphorylation of clock proteins represents an important mechanism regulating circadian clocks. InNeurospora, clock protein FREQUENCY (FRQ) is progressively phosphorylated over time, and its level decreases when it is extensively phosphorylated. To identify the kinase phosphorylating FRQ and to understand the function of FRQ phosphorylation, a FRQ-phosphorylating kinase was purified and identified as casein kinase II (CKII). Disruption of the catalytic subunit gene of CKII inNeurospora resulted in hypophosphorylation and increased levels of FRQ protein. In addition, the circadian rhythms offrq RNA, FRQ protein, and clock-controlled genes are abolished in the CKII mutant. Our data suggest that the phosphorylation of FRQ by CKII may have at least three functions; it decreases the stability of FRQ, reduces the protein complex formation between FRQ and the WHITE COLLAR proteins, and is important for the closing of theNeurospora circadian negative feedback loop. Taken together, our results suggest that CKII is an important component of theNeurospora circadian clock.
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Footnotes
↵1 Corresponding author.
E-MAILYi.Liu{at}UTsouthwestern.edu; FAX (214) 648-7891.
Article and publication are at http://www.genesdev.org/cgi/doi/10.1101/gad.965102.
- Received November 27, 2001.
- Accepted February 27, 2002.
- Cold Spring Harbor Laboratory Press
