TY - JOUR
T1 - Phosphorylation of the transcription activator CLOCK regulates progression through a ∼24-h feedback loop to influence the circadian period in drosophila
AU - Mahesh, Guruswamy
AU - Jeong, Eun Hee
AU - Ng, Fanny S.
AU - Liu, Yixiao
AU - Gunawardhana, Kushan
AU - Houl, Jerry H.
AU - Yildirim, Evrim
AU - Amunugama, Ravi
AU - Jones, Richard
AU - Allen, David L.
AU - Edery, Isaac
AU - Kim, Eun Young
AU - Hardin, Paul E.
PY - 2014/7/11
Y1 - 2014/7/11
N2 - Circadian (≅24 h) clocks control daily rhythms in metabolism, physiology, and behavior in animals, plants, and microbes. In Drosophila, these clocks keep circadian time via transcriptional feedback loops in which CLOCK-CYCLE (CLK-CYC) initiates transcription of period (per) and timeless (tim), accumulating levels of PER and TIM proteins feed back to inhibit CLK-CYC, and degradation of PER and TIM allows CLK-CYCto initiate the next cycle of transcription. The timing of key events in this feedback loop are controlled by, or coincide with, rhythms in PER and CLK phosphorylation, where PER and CLK phosphorylation is high during transcriptional repression. PER phosphorylation at specific sites controls its subcellular localization, activity, and stability, but comparatively little is known about the identity and function of CLK phosphorylation sites. Here we identify eight CLK phosphorylation sites via mass spectrometry and determine how phosphorylation at these sites impacts behavioral and molecular rhythms by transgenic rescue of a new Clk null mutant. Eliminating phosphorylation at four of these sites accelerates the feedback loop to shorten the circadian period, whereas loss of CLK phosphorylation at serine 859 increases CLK activity, thereby increasing PER levels and accelerating transcriptional repression. These results demonstrate that CLK phosphorylation influences the circadian period by regulating CLK activity and progression through the feedback loop.
AB - Circadian (≅24 h) clocks control daily rhythms in metabolism, physiology, and behavior in animals, plants, and microbes. In Drosophila, these clocks keep circadian time via transcriptional feedback loops in which CLOCK-CYCLE (CLK-CYC) initiates transcription of period (per) and timeless (tim), accumulating levels of PER and TIM proteins feed back to inhibit CLK-CYC, and degradation of PER and TIM allows CLK-CYCto initiate the next cycle of transcription. The timing of key events in this feedback loop are controlled by, or coincide with, rhythms in PER and CLK phosphorylation, where PER and CLK phosphorylation is high during transcriptional repression. PER phosphorylation at specific sites controls its subcellular localization, activity, and stability, but comparatively little is known about the identity and function of CLK phosphorylation sites. Here we identify eight CLK phosphorylation sites via mass spectrometry and determine how phosphorylation at these sites impacts behavioral and molecular rhythms by transgenic rescue of a new Clk null mutant. Eliminating phosphorylation at four of these sites accelerates the feedback loop to shorten the circadian period, whereas loss of CLK phosphorylation at serine 859 increases CLK activity, thereby increasing PER levels and accelerating transcriptional repression. These results demonstrate that CLK phosphorylation influences the circadian period by regulating CLK activity and progression through the feedback loop.
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U2 - 10.1074/jbc.M114.568493
DO - 10.1074/jbc.M114.568493
M3 - Article
C2 - 24872414
AN - SCOPUS:84904201438
SN - 0021-9258
VL - 289
SP - 19681
EP - 19693
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 28
ER -