Identification of a Calcium/Calmodulin-dependent Protein Kinase That Phosphorylates the Neurospora Circadian Clock Protein FREQUENCY

Yuhong Yang, Ping Cheng, Gang Zhi, Yi Liu

Research output: Contribution to journalArticle

84 Scopus citations

Abstract

Phosphorylation of circadian clock proteins represents a major regulatory step that controls circadian clocks. In Neurospora, the circadian clock protein FREQUENCY (FRQ) is progressively phosphorylated over time, and its level decreases when it is hyperphosphorylated. In this study, we showed that most of the kinase activity phosphorylating FRQ in vitro was calcium/ calmodulin-dependent, and the endogenous FRQ in the Neurospora extracts was phosphorylated by a Ca/ CaM-dependent kinase-like activity. From Neurospora cell extracts, an ∼50-kDa Ca/CaM-dependent kinase (CAMK-1) that can specifically phosphorylate FRQ was purified. In vitro, this kinase accounts for near half of the FRQ kinase activity, and it can phosphorylate the FRQ region that contains the three known functionally important phosphorylation sites. To understand the function of camk-I in vivo, it was disrupted in Neurospora by gene replacement. After germination from ascospores, the camk-1 null strains grew slowly, indicating that CAMK-1 plays an important role in growth and development of Neurospora. This phenotype was transient however, revealing redundancy in the system. Analysis of the camk-1 null strain revealed that the deletion of camk-1 affected phase, period, and light-induced phase shifting of the circadian conidiation rhythm. Taken together, our results suggest that multiple kinases may phosphorylate FRQ in vivo.

Original languageEnglish (US)
Pages (from-to)41064-41072
Number of pages9
JournalJournal of Biological Chemistry
Volume276
Issue number44
DOIs
StatePublished - Nov 2 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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