Abstract
Circadian rhythms in mammals are driven by a feedback loop in which the transcription factor Clock-Bmal1 activates expression of Per and Cry proteins, which together form a large nuclear complex (Per complex) that represses Clock-Bmal1 activity. We found that mouse Clock-Bmal1 recruits the Ddb1-Cullin-4 ubiquitin ligase to Per (Per1 and Per2), Cry (Cry1 and Cry2) and other circadian target genes. Histone H2B monoubiquitination at Per genes was rhythmic and depended on Bmal1, Ddb1 and Cullin-4a. Depletion of Ddb1-Cullin-4a or an independent decrease in H2B monoubiquitination caused defective circadian feedback and decreased the association of the Per complex with DNA-bound Clock-Bmal1. Clock-Bmal1 thus covalently marks Per genes for subsequent recruitment of the Per complex. Our results reveal a chromatin-mediated signal from the positive to the negative limb of the clock that provides a licensing mechanism for circadian feedback.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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ARNTL Transcription Factors / metabolism
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Animals
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CLOCK Proteins / metabolism
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Chromatin Immunoprecipitation
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Chromatography, Liquid
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Circadian Rhythm / genetics
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Circadian Rhythm / physiology*
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Cullin Proteins / metabolism
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DNA Primers / genetics
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DNA-Binding Proteins / metabolism
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Feedback, Physiological / physiology*
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Histones / metabolism*
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Immunoblotting
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Mice
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Mice, Inbred C57BL
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Multiprotein Complexes / metabolism*
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Oligopeptides / genetics
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Period Circadian Proteins / metabolism*
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Real-Time Polymerase Chain Reaction
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Tandem Mass Spectrometry
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Ubiquitination
Substances
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ARNTL Transcription Factors
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Bmal1 protein, mouse
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Cul4a protein, mouse
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Cullin Proteins
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DNA Primers
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DNA-Binding Proteins
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Ddb1 protein, mouse
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Histones
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Multiprotein Complexes
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Oligopeptides
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Per1 protein, mouse
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Per2 protein, mouse
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Period Circadian Proteins
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CLOCK Proteins
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Clock protein, mouse