Nucleic Acids Research Advance Access originally published online on January 7, 2009
Nucleic Acids Research 2009 37(4):1115-1126; doi:10.1093/nar/gkn1013
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Nucleic Acids Research, 2009, Vol. 37, No. 4 1115-1126
© 2009 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Molecular Biology |
Molecular characterization of Mybbp1a as a co-repressor on the Period2 promoter
1Clock Cell Biology, Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8566 and 2Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8576, Japan
*To whom correspondence should be addressed. Tel: +81 298 61 6053; Fax: +81 298 61 9499; Email: n.ishida{at}aist.go.jp
Received November 11, 2008. Accepted December 4, 2008.
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.