Abstract
Recent studies have shown that casein kinase I epsilon (CKIepsilon) is an essential regulator of the mammalian circadian clock. However, the detailed mechanisms by which CKIepsilon regulates each component of the circadian negative-feedback loop have not been fully defined. We show here that mPer proteins, negative limbs of the autoregulatory loop, are specific substrates for CKIepsilon and CKIdelta. The CKI phosphorylation of mPer1 and mPer3 proteins results in their rapid degradation, which is dependent on the ubiquitin-proteasome pathway. Moreover, CKIepsilon and CKIdelta are able to induce nuclear translocation of mPer3, which requires its nuclear localization signal. The mutation in potential phosphorylation sites on mPer3 decreased the extent of both nuclear translocation and degradation of mPer3 that are stimulated by CKIepsilon. CKIepsilon and CKIdelta affected the inhibitory effect of mPer proteins on the transcriptional activity of BMAL1-CLOCK, but the inhibitory effect of mCry proteins on the activity of BMAL1-CLOCK was unaffected. These results suggest that CKIepsilon and CKIdelta regulate the mammalian circadian autoregulatory loop by controlling both protein turnover and subcellular localization of mPer proteins.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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ARNTL Transcription Factors
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Active Transport, Cell Nucleus / physiology
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Animals
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Basic Helix-Loop-Helix Transcription Factors
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Binding Sites / physiology
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COS Cells
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Casein Kinases
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Cell Cycle Proteins
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Circadian Rhythm / physiology
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Cysteine Endopeptidases / metabolism
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Feedback, Physiological / drug effects
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Feedback, Physiological / physiology
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Intracellular Fluid / metabolism
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Mice
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Multienzyme Complexes / metabolism
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Nuclear Localization Signals / physiology
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism*
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Period Circadian Proteins
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Phosphorylation
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Proteasome Endopeptidase Complex
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Protein Binding / physiology
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Protein Kinases / metabolism*
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Protein Kinases / pharmacology
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Transcription Factors / metabolism
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Transcription, Genetic / drug effects
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Transcription, Genetic / physiology
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Ubiquitin / metabolism
Substances
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ARNTL Transcription Factors
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Bmal1 protein, mouse
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Basic Helix-Loop-Helix Transcription Factors
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Cell Cycle Proteins
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Multienzyme Complexes
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Nuclear Localization Signals
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Nuclear Proteins
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Per1 protein, mouse
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Per2 protein, mouse
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Per3 protein, mouse
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Period Circadian Proteins
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Transcription Factors
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Ubiquitin
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Protein Kinases
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Casein Kinases
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Cysteine Endopeptidases
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Proteasome Endopeptidase Complex