Abstract
Tissue-specific overexpression of the glycogen synthase kinase-3 (GSK-3) ortholog shaggy (sgg) shortens the period of the Drosophila circadian locomotor activity cycle. The short period phenotype was attributed to premature nuclear translocation of the PERIOD/TIMELESS heterodimer. Reducing SGG/GSK-3 activity lengthens period, demonstrating an intrinsic role for the kinase in circadian rhythmicity. Lowered sgg activity decreased TIMELESS phosphorylation, and it was found that GSK-3 beta specifically phosphorylates TIMELESS in vitro. Overexpression of sgg in vivo converts hypophosphorylated TIMELESS to a hyperphosphorylated protein whose electrophoretic mobility, and light and phosphatase sensitivity, are indistinguishable from the rhythmically produced hyperphosphorylated TIMELESS of wild-type flies. Our results indicate a role for SGG/GSK-3 in TIMELESS phosphorylation and in the regulated nuclear translocation of the PERIOD/TIMELESS heterodimer.
Publication types
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Active Transport, Cell Nucleus
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Animals
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Biological Clocks / genetics
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Biological Clocks / physiology*
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Cell Nucleus / metabolism
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Circadian Rhythm / genetics
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Circadian Rhythm / physiology*
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Dimerization
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Drosophila Proteins*
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Drosophila melanogaster / embryology
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Drosophila melanogaster / genetics
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Drosophila melanogaster / physiology*
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Glycogen Synthase Kinase 3*
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Immunoblotting
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Insect Proteins / genetics
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Insect Proteins / metabolism*
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Microscopy, Fluorescence
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Motor Activity / genetics
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Motor Activity / physiology
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Nuclear Proteins / metabolism*
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Period Circadian Proteins
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Phosphorylation
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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RNA / genetics
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RNA / metabolism
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
Substances
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Drosophila Proteins
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Insect Proteins
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Nuclear Proteins
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PER protein, Drosophila
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Period Circadian Proteins
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Recombinant Fusion Proteins
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tim protein, Drosophila
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RNA
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Protein Serine-Threonine Kinases
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Sgg protein, Drosophila
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Glycogen Synthase Kinase 3