Transforming Growth Factor-β1-induced Transcript 1 Protein, a Novel Marker for Smooth Muscle Contractile Phenotype, Is Regulated by Serum Response Factor/Myocardin Protein
Transforming Growth Factor-β1-induced Transcript 1 Protein, a Novel Marker for Smooth Muscle Contractile Phenotype, Is Regulated by Serum Response Factor/Myocardin Protein
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DOI：
10.1074/jbc.m111.250878
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发表时间：
2011-12-02
影响因子：
4.8
通讯作者：
Zhou, Jiliang
中科院分区：
文献类型：
--
作者：
Wang, Xiaobo;Hu, Guoqing;Zhou, Jiliang
血清反应因子（SRF）在调节平滑肌特异性基因的表达中起着重要作用，部分是通过与有效的组织特异性辅因子myocardin相关联。以前的研究表明，转化生长因子β 1诱导的转录本1（TGF-β 1 I1，也称为Hic-5）是一个TGF-β反应基因，并参与血管损伤的细胞反应，但TGF-β 1 I1表达的调控仍然难以捉摸。在这份报告中，我们证明了TGFB 1 I1是一种新的平滑肌收缩表型的标志物，并受到SRF/myocardin的调控。我们发现TGFB 1 I1在平滑肌细胞（SMC）和富含平滑肌的组织中特异性表达。此外，TGFB 1 I1表达在多种平滑肌表型调节模型中显著下调。TGFB 1 I1启动子含有一个进化上保守的CArG元件，该元件是心肌素诱导TGFB 1 I1启动子反式激活所必需的。通过寡核苷酸下拉和染色质免疫沉淀试验，我们发现SRI结合到这个CArG元件在体外和体内。心肌素的异位表达足以诱导多种细胞系中的内源性TGFB 1 I1表达，而敲低心肌素或SRF显著减弱SMC中的TGFB 1 I1表达。此外，我们的数据表明，SRF是必不可少的TGF-β介导的诱导TGFB 1 I1。最后，TGFB 1 I1表达的沉默显著促进SMC增殖。总的来说，这项研究提供了第一个证据，TGFB 1 I1不仅是一个SRF/myocardin调节的平滑肌标志物，但也是通过抑制平滑肌增殖维持平滑肌收缩表型的关键。
Serum response factor (SRF) plays a central role in regulating expression of smooth muscle-specific genes partly by associating with the potent tissue-specific cofactor myocardin. Previous studies have shown that transforming growth factor-beta 1-induced transcript 1 (TGFB1I1, also known as Hic-5) is a TGF-beta-responsive gene and is involved in the cellular response to vascular injury, but the regulation of TGFB1I1 expression remains elusive. In this report, we demonstrated that TGFB1I1 is a novel marker for the smooth muscle contractile phenotype and is regulated by SRF/myocardin. We found that TGFB1I1 is specifically expressed in smooth muscle cells (SMCs) and in smooth muscle-rich tissues. Furthermore, TGFB1I1 expression is significantly down-regulated in a variety of models for smooth muscle phenotypic modulation. The TGFB1I1 promoter contains an evolutionarily conserved CArG element, and this element is indispensible for myocardin-induced transactivation of TGFB1I1 promoter. By oligonucleotide pulldown and chromatin immunoprecipitation assays, we found that SRI binds to this CArG element in vitro and in vivo. Ectopic expression of myocardin is sufficient to induce endogenous TGFB1I1 expression in multiple cell lines whereas knocking-down myocardin or SRF significantly attenuated TGFB1I1 expression in SMCs. Furthermore, our data demonstrated that SRF is essential for TGF-beta-mediated induction of TGFB1I1. Finally, silencing of TGFB1I1 expression significantly promotes SMC proliferation. Collectively, this study provides the first evidence that TGFB1I1 is not only an SRF/myocardin-regulated smooth muscle marker but also critical for maintaining smooth muscle contractile phenotype by inhibiting smooth muscle proliferation.