title: Circadian mutant Overtime reveals F-box protein FBXL3 regulation of cryptochrome and period gene expression.
abstract: Using a forward genetics ENU mutagenesis screen for recessive mutations that affect circadian rhythmicity in the mouse, we isolated a long period (approximately 26 hr) circadian mutant named Overtime (Ovtm). Positional cloning and genetic complementation reveal that Ovtm is encoded by the F-box protein FBXL3, a component of the SKP1-CUL1-F-box-protein (SCF) E3 ubiquitin ligase complex. The Ovtm mutation causes an isoleucine to threonine (I364T) substitution leading to a loss of function in FBXL3, which interacts specifically with the CRYPTOCHROME (CRY) proteins. In Ovtm mice, expression of the PERIOD proteins PER1 and PER2 is reduced; however, the CRY proteins CRY1 and CRY2 are unchanged. The loss of FBXL3 function leads to a stabilization of the CRY proteins, which in turn leads to a global transcriptional repression of the Per and Cry genes. Thus, Fbxl3(Ovtm) defines a molecular link between CRY turnover and CLOCK/BMAL1-dependent circadian transcription to modulate circadian period.
authors.affiliation: Howard Hughes Medical Institute, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA.
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Siepka
authors.forename: Seung-Hee
authors.initials: SH
authors.lastname: Yoo
authors.forename: Junghea
authors.initials: J
authors.lastname: Park
authors.forename: Weimin
authors.initials: W
authors.lastname: Song
authors.forename: Vivek
authors.initials: V
authors.lastname: Kumar
authors.forename: Yinin
authors.initials: Y
authors.lastname: Hu
authors.forename: Choogon
authors.initials: C
authors.lastname: Lee
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001683:Biological Clocks; D018797:Cell Cycle Proteins / Q000235:genetics*; D002940:Circadian Rhythm; D056931:Cryptochromes; D044783:F-Box Proteins / Q000235:genetics*; D005260:Female; D005420:Flavoproteins / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000235:genetics*; D056950:Period Circadian Proteins; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: C538963:CRY1 protein, human; C538966:CRY2 protein, human; D018797:Cell Cycle Proteins; C538964:Cry1 protein, mouse; C538967:Cry2 protein, mouse; D056931:Cryptochromes; D044783:F-Box Proteins; C519794:Fbxl3 protein, mouse; D005420:Flavoproteins; D009687:Nuclear Proteins; C539022:PER1 protein, human; C539023:Per1 protein, mouse; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D014157:Transcription Factors