Nucleic Acids Research Advance Access published online on May 22, 2009
Nucleic Acids Research, doi:10.1093/nar/gkp398
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Gene Regulation, Chromatin and Epigenetics |
RFXB and its splice variant RFXBSV mediate the antagonism between IFN
and TGFβ on COL1A2 transcription in vascular smooth muscle cells
1Atherosclerosis Research Center, Key Laboratory of Human Functional Genomics, 2Department of Pathophysiology, Nanjing Medical University, Nanjing, Jiangsu 210029, 3Jiangsu Staff Medical University, Nanjing, Jiangsu 210029, China
*To whom correspondence should be addressed. Tel: +86 25 86862888; Fax: +86 25 86862888; Email: yxu2005{at}gmail.com
Received November 18, 2008. Revised April 10, 2009. Accepted May 1, 2009.
Cytokines secreted by infiltrating immune cells during atherogenesis modulate vascular remodeling. One exemplary event is the antagonism between transformed growth factor (TGF-β) and interferon gamma (IFN-
) on the transcriptional control of type I collagen gene (COL1A2). Previously we have reported that IFN- up-regulates regulatory factor for X-box B (RFXB) to repress collagen transcription while down-regulates the expression of RFXBSV, a splice variant of RFXB that blocks collagen repression in fibroblasts. Here we demonstrate that TGF-β abrogated COL1A2 repression by IFN- through altering the relative expression of RFXB and RFXBSV. Unlike RFXB, RFXBSV did not bind to the collagen promoter and competed with RFXB for the co-repressor histone deacetylase 2 (HDAC2), limiting HDAC2 recruitment to the collagen transcription start site as evidenced by chromatin immunoprecipitation assays. Over-expression of RFXB by lentiviral infection in HASMCs enhanced HDAC2 enlistment, promoted histone deacetylation surrounding the collagen site by IFN-, and blocked the TGF-β antagonism, a pattern reversed by RFXBSV infection. On the contrary, silencing of RFXB, but not both RFXB and RFXBSV, expression promoted the TGF-β antagonism. Thus, we have identified a novel mechanism whereby TGF-β antagonizes the IFN- repression of collagen transcription in HASMCs and as such provided new insights into antiatherogenic strategies.