title: Molecular characterization of Mybbp1a as a co-repressor on the Period2 promoter.
abstract: The circadian clock comprises transcriptional feedback loops of clock genes. Cryptochromes are essential components of the negative feedback loop in mammals as they inhibit CLOCK-BMAL1-mediated transcription. We purified mouse CRY1 (mCRY1) protein complexes from Sarcoma 180 cells to determine their roles in circadian gene expression and discovered that Myb-binding protein 1a (Mybbp1a) interacts with mCRY1. Mybbp1a regulates various transcription factors, but its role in circadian gene expression is unknown. We found that Mybbp1a functions as a co-repressor of Per2 expression and repressed Per2 promoter activity in reporter assays. Chromatin immunoprecipitation (ChIP) assays revealed endogenous Mybbp1a binding to the Per2 promoter that temporally matched that of mCRY1. Furthermore, Mybbp1a binding to the Per2 promoter correlated with the start of the down-regulation of Per2 expression and with the dimethylation of histone H3 Lys9, to which it could also bind. These findings suggest that Mybbp1a and mCRY1 can form complexes on the Per2 promoter that function as negative regulators of Per2 expression.
authors.affiliation: Clock Cell Biology, Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Hara
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Onishi
authors.forename: Katsutaka
authors.initials: K
authors.lastname: Oishi
authors.forename: Koyomi
authors.initials: K
authors.lastname: Miyazaki
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Fukamizu
authors.forename: Norio
authors.initials: N
authors.lastname: Ishida
mesh_terms: D000818:Animals; D056926:CLOCK Proteins; D002352:Carrier Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics*; D002460:Cell Line; D002940:Circadian Rhythm / Q000235:genetics*; D056931:Cryptochromes; D004268:DNA-Binding Proteins; D005420:Flavoproteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006657:Histones / Q000737:chemistry / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D056950:Period Circadian Proteins; D011401:Promoter Regions, Genetic; D016601:RNA-Binding Proteins; D012097:Repressor Proteins / Q000378:metabolism*; D012510:Sarcoma 180 / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C538964:Cry1 protein, mouse; D056931:Cryptochromes; D004268:DNA-Binding Proteins; D005420:Flavoproteins; D006657:Histones; C110421:Mybbp1a protein, mouse; D009687:Nuclear Proteins; C513312:Per2 protein, mouse; D056950:Period Circadian Proteins; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D056926:CLOCK Proteins; C538944:Clock protein, mouse; D008239:Lysine