title: Activating PER repressor through a DBT-directed phosphorylation switch.
abstract: Protein phosphorylation plays an essential role in the generation of circadian rhythms, regulating the stability, activity, and subcellular localization of certain proteins that constitute the biological clock. This study examines the role of the protein kinase Doubletime (DBT), a Drosophila ortholog of human casein kinase I (CKI)epsilon/delta. An enzymatically active DBT protein is shown to directly phosphorylate the Drosophila clock protein Period (PER). DBT-dependent phosphorylation sites are identified within PER, and their functional significance is assessed in a cultured cell system and in vivo. The per(S) mutation, which is associated with short-period (19-h) circadian rhythms, alters a key phosphorylation target within PER. Inspection of this and neighboring sequence variants indicates that several DBT-directed phosphorylations regulate PER activity in an integrated fashion: Alternative phosphorylations of two adjoining sequence motifs appear to be associated with switch-like changes in PER stability and repressor function.
authors.affiliation: Laboratory of Genetics, The Rockefeller University, New York, New York, USA.
authors.forename: Saul
authors.initials: S
authors.lastname: Kivimäe
authors.forename: Lino
authors.initials: L
authors.lastname: Saez
authors.forename: Michael W
authors.initials: MW
authors.lastname: Young
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D048149:Casein Kinase 1 epsilon / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002940:Circadian Rhythm; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D056950:Period Circadian Proteins; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000378:metabolism; D018411:Spodoptera
chemical_list: D029721:Drosophila Proteins; D009687:Nuclear Proteins; C539040:PER protein, Drosophila; D056950:Period Circadian Proteins; D011994:Recombinant Proteins; D048149:Casein Kinase 1 epsilon