title: Identification of a novel vertebrate circadian clock-regulated gene encoding the protein nocturnin.
abstract: Photoreceptors of the Xenopus laevis retina are the site of a circadian clock. As part of a differential display screen for rhythmic gene products in this system, we have identified a photoreceptor-specific mRNA expressed in peak abundance at night. cDNA cloning revealed an open reading frame encoding a putative 388 amino acid protein that we have named "nocturnin" (for night-factor). This protein has strong sequence similarity to the C-terminal domain of the yeast transcription factor, CCR4, as well as a leucine zipper-like dimerization motif. Nocturnin mRNA levels exhibit a high amplitude circadian rhythm and nuclear run-on analysis indicates that it is controlled by the retinal circadian clock at the level of transcription. Our observations suggest that nocturnin may function through protein-protein interaction either as a component of the circadian clock or as a downstream effector of clock function.
authors.affiliation: Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City 66160-7400, USA.
authors.forename: C B
authors.initials: CB
authors.lastname: Green
authors.forename: J C
authors.initials: JC
authors.lastname: Besharse
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002940:Circadian Rhythm / Q000235:genetics*; D003001:Cloning, Molecular; D005796:Genes; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011506:Proteins / Q000235:genetics*; D016415:Sequence Alignment; D014157:Transcription Factors; D014714:Vertebrates; D014981:Xenopus
chemical_list: D009687:Nuclear Proteins; D011506:Proteins; D014157:Transcription Factors; C102804:nocturnin