Molecular and Cellular Biology, October 2005, p. 8415-8429, Vol. 25, No. 19
0270-7306/05/$08.00+0 doi:10.1128/MCB.25.19.8415-8429.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Tumor Suppressor SMAR1 Mediates Cyclin D1 Repression by Recruitment of the SIN3/Histone Deacetylase 1 Complex
Shravanti Rampalli,1
L. Pavithra,1
Altaf Bhatt,2
Tapas K. Kundu,2 and
Samit Chattopadhyay*
National Centre for Cell Science, Pune University Campus, Ganeshkhind, Pune 411007, India,1
Jawharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore 560064, India2
Received 5 May 2005/
Returned for modification 13 June 2005/
Accepted 6 July 2005
Matrix attachment region binding proteins have been shown to play an important role in gene regulation by altering chromatin in a stage- and tissue-specific manner. Our previous studies report that SMAR1, a matrix-associated protein, regresses B16-F1-induced tumors in mice. Here we show SMAR1 targets the cyclin D1 promoter, a gene product whose dysregulation is attributed to breast malignancies. Our studies reveal that SMAR1 represses cyclin D1 gene expression, which can be reversed by small interfering RNA specific to SMAR1. We demonstrate that SMAR1 interacts with histone deacetylation complex 1, SIN3, and pocket retinoblastomas to form a multiprotein repressor complex. This interaction is mediated by the SMAR1(160-350) domain. Our data suggest SMAR1 recruits a repressor complex to the cyclin D1 promoter that results in deacetylation of chromatin at that locus, which spreads to a distance of at least the 5 kb studied upstream of the cyclin D1 promoter. Interestingly, we find that the high induction of cyclin D1 in breast cancer cell lines can be correlated to the decreased levels of SMAR1 in these lines. Our results establish the molecular mechanism exhibited by SMAR1 to regulate cyclin D1 by modification of chromatin.
* Corresponding author. Mailing address: National Center for Cell Science, Pune University Campus, Ganeshkhind, Pune 411007, India. Phone: 91-20-2569-0922. Fax: 91-20-2569-2259. E-mail: samit{at}nccs.res.in.
Supplemental material for this article may be found at http://mcb.asm.org/.
Molecular and Cellular Biology, October 2005, p. 8415-8429, Vol. 25, No. 19
0022-538X/05/$08.00+0 doi:10.1128/MCB.25.19.8415-8429.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
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Copyright © 2005 by the American Society for Microbiology. All rights reserved.