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.
Pubmed ID: 19129230 RIS Download
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A package of over twenty mass spectrometry-based tools primarily geared toward proteomic data analysis and database mining. It can be run from the command line, but is primarily used through a web browser, and there is a public website that allows anyone to use the software without local installation. Tandem mass spectrometry analysis tools are used for database searching and identification of peptides, including post-translationally modified peptides and cross-linked peptides. Support for isotope and label-free quantification from this type of data is provided. MS-Viewer software allows sharing and displaying of annotated spectra from many different tandem mass spectrometry data analysis packages. Other tools include software for analyzing peptide mass fingerprinting data (MS-Fit); prediction of theoretical fragmentation of peptides (MS-Product); theoretical chemical or enzymatic digestion of proteins (MS-Digest); and theoretical modeling of the isotope distribution of any chemical, including peptides (MS-Isotope). Searches using amino acid sequence can be used to identify homologous peptides in a database (MS-Pattern); the use of the combination of amino acid sequence and masses can be used for homologous peptide and protein identification using MS-Homology. Tandem mass spectrometry peak list files can be filtered for the presence of certain peaks or neutral losses using MS-Filter. Given a list of proteins, MS-Bridge can report all potential cross-linked peptide combinations of a specified mass. Given a precursor peptide mass and information about known amino acid presence, absence, or modifications, MS-Comp can report all amino acid combinations that could lead to the observed mass.
View all literature mentionsCell line NIH 3T3 is a Spontaneously immortalized cell line with a species of origin Mus musculus
View all literature mentionsCell line COS-1 is a Transformed cell line with a species of origin Chlorocebus aethiops (Green monkey)
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