TY - JOUR
T1 - Light-independent phosphorylation of WHITE COLLAR-I regulates its function in the Neurospora circadian negative feedback loop
AU - He, Qiyang
AU - Shu, Hongjun
AU - Cheng, Ping
AU - Chen, She
AU - Wang, Lixin
AU - Liu, Yi
PY - 2005/4/29
Y1 - 2005/4/29
N2 - Phosphorylation is a major regulatory mechanism controlling circadian clocks. In the Neurospora circadian clock, the PER-AKNT-SIM (PAS) domain-containing transcription factor, WHITE COLLAR (WC)-1, acts both as the blue light photoreceptor of the clock and as a positive element in the circadian negative feedback loop in constant darkness, by activating the transcription of the frequency (frq) gene. To understand the role of WC-1 phosphorylation, five in vivo WC-1 phosphorylation sites, located immediately downstream of the WC-1 zinc finger DNA binding domain, were identified by tandem mass spectrometry using biochemically purified endogenous WC-1 protein. Mutations of these phosphorylation sites suggest that they are major WC-1 phosphorylation sites under constant conditions but are not responsible for the light-induced hyperphosphorylation of WC-1. Although phosphorylation of these sites does not affect the light function of WC-1, strains carrying mutations of these sites show short period, low amplitude, or arrhythmic conidiation rhythms in constant darkness. Furthermore, normal or slightly higher levels of frq mRNA and FRQ proteins were observed in a mutant strain containing mutations of all five sites despite its low WC-1 levels. Together, these data suggest that phosphorylation of these sites negatively regulates the function of WC-1 in the circadian negative feedback loop and is important for the function of the Neurospora circadian clock.
AB - Phosphorylation is a major regulatory mechanism controlling circadian clocks. In the Neurospora circadian clock, the PER-AKNT-SIM (PAS) domain-containing transcription factor, WHITE COLLAR (WC)-1, acts both as the blue light photoreceptor of the clock and as a positive element in the circadian negative feedback loop in constant darkness, by activating the transcription of the frequency (frq) gene. To understand the role of WC-1 phosphorylation, five in vivo WC-1 phosphorylation sites, located immediately downstream of the WC-1 zinc finger DNA binding domain, were identified by tandem mass spectrometry using biochemically purified endogenous WC-1 protein. Mutations of these phosphorylation sites suggest that they are major WC-1 phosphorylation sites under constant conditions but are not responsible for the light-induced hyperphosphorylation of WC-1. Although phosphorylation of these sites does not affect the light function of WC-1, strains carrying mutations of these sites show short period, low amplitude, or arrhythmic conidiation rhythms in constant darkness. Furthermore, normal or slightly higher levels of frq mRNA and FRQ proteins were observed in a mutant strain containing mutations of all five sites despite its low WC-1 levels. Together, these data suggest that phosphorylation of these sites negatively regulates the function of WC-1 in the circadian negative feedback loop and is important for the function of the Neurospora circadian clock.
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U2 - 10.1074/jbc.M414010200
DO - 10.1074/jbc.M414010200
M3 - Article
C2 - 15731099
AN - SCOPUS:20444444274
SN - 0021-9258
VL - 280
SP - 17526
EP - 17532
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 17
ER -