title: A key temporal delay in the circadian cycle of Drosophila is mediated by a nuclear localization signal in the timeless protein.
abstract: Regulated nuclear entry of the Period (PER) and Timeless (TIM) proteins, two components of the Drosophila circadian clock, is essential for the generation and maintenance of circadian behavior. PER and TIM shift from the cytoplasm to the nucleus daily, and the length of time that PER and TIM reside in the cytoplasm is an important determinant of the period length of the circadian rhythm. Here we identify a TIM nuclear localization signal (NLS) that is required for appropriately timed nuclear accumulation of both TIM and PER. Transgenic flies with a mutated TIM NLS produced circadian rhythms with a period of ∼30 hr. In pacemaker cells of the brain, PER and TIM proteins rise to abnormally high levels in the cytoplasm of tim(ΔNLS) mutants, but show substantially reduced nuclear accumulation. In cultured S2 cells, the mutant TIM(ΔNLS) protein significantly delays nuclear accumulation of both TIM and wild-type PER proteins. These studies confirm that TIM is required for the nuclear localization of PER and point to a key role for the TIM NLS in the regulated nuclear accumulation of both proteins.
authors.affiliation: Laboratory of Genetics, The Rockefeller University, New York, New York 10065, USA.
authors.forename: Lino
authors.initials: L
authors.lastname: Saez
authors.forename: Mary
authors.initials: M
authors.lastname: Derasmo
authors.forename: Pablo
authors.initials: P
authors.lastname: Meyer
authors.forename: J
authors.initials: J
authors.lastname: Stieglitz
authors.forename: Michael W
authors.initials: MW
authors.lastname: Young
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D015152:Blotting, Northern; D015153:Blotting, Western; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D057906:Circadian Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D003433:Crosses, Genetic; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000502:physiology; D018613:Microscopy, Confocal; D019913:Nuclear Localization Signals / Q000172:deficiency / Q000235:genetics; D056950:Period Circadian Proteins / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D017384:Sequence Deletion; D014158:Transcription, Genetic
chemical_list: D029721:Drosophila Proteins; D019913:Nuclear Localization Signals; C539040:PER protein, Drosophila; D056950:Period Circadian Proteins; C096445:tim protein, Drosophila