DOUBLETIME plays a noncatalytic role to mediate CLOCK phosphorylation and repress CLOCK-dependent transcription within the Drosophila circadian clock.
Circadian clocks keep time via gene expression feedback loops that are controlled by time-of-day-specific changes in the synthesis, activity, and degradation of transcription factors. Within the Drosophila melanogaster circadian clock, DOUBLETIME (DBT) kinase is necessary for the phosphorylation of PERIOD (PER), a transcriptional repressor, and CLOCK (CLK), a transcriptional activator, as CLK-dependent transcription is being repressed. PER- and DBT-containing protein complexes feed back to repress CLK-dependent transcription, but how DBT promotes PER and CLK phosphorylation and how PER and CLK phosphorylation contributes to transcriptional repression have not been defined. Here, we show that DBT catalytic activity is not required for CLK phosphorylation or transcriptional repression and that PER phosphorylation is dispensable for repressing CLK-dependent transcription. These results support a model in which DBT plays a novel noncatalytic role in recruiting additional kinases that phosphorylate CLK, thereby repressing transcription. A similar mechanism likely operates in mammals, given the conserved activities of PER, DBT, and CLK orthologs.
Yu
Wangjie
W
Department of Biology, Texas A&M University, College Station, TX 77843, USA.
Zheng
Hao
H
Price
Jeffrey L
JL
Hardin
Paul E
PE
D000818:Animals; D056926:CLOCK Proteins; D048149:Casein Kinase 1 epsilon / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D004330:Drosophila / Q000378:metabolism / Q000502:physiology*; D029721:Drosophila Proteins / Q000378:metabolism* / Q000502:physiology*; D009687:Nuclear Proteins / Q000502:physiology; D056950:Period Circadian Proteins; D010766:Phosphorylation; D011485:Protein Binding; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
C120526:Clk protein, Drosophila; D029721:Drosophila Proteins; D009687:Nuclear Proteins; C539040:PER protein, Drosophila; D056950:Period Circadian Proteins; D014157:Transcription Factors; C113519:dco protein, Drosophila; D056926:CLOCK Proteins; D048149:Casein Kinase 1 epsilon