Regulation of MicroRNAs by Brahma-related Gene 1 (Brg1) in Smooth Muscle Cells
Regulation of MicroRNAs by Brahma-related Gene 1 (Brg1) in Smooth Muscle Cells
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DOI：
10.1074/jbc.m112.409474
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发表时间：
2013-03-01
影响因子：
4.8
通讯作者：
Herring, B. Paul
中科院分区：
文献类型：
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作者：
Chen, Meng;Herring, B. Paul
MicroRNA参与平滑肌细胞（SMC）的表型转换。含Brg 1的SWI/SNF染色质重塑复合物在控制SMC表型中也起重要作用。因此，我们确定Brg 1是否影响SMCs中microRNA的转录。对来自Brg 1平滑肌特异性缺失小鼠的平滑肌的微阵列和定量RT-PCR分析显示了几种microRNA的表达改变，包括miR-143/145和miR-133。通过显性负性Brg 1表达或Brg 1敲除体外SMC中Brg 1的消融减弱了miR-143/145表达。SMCs中血清反应因子（SRF）的敲低显著降低了miR-143/145和miR-133的表达水平，而myocardin的敲低仅减弱了miR-143/145的表达。在10 T1/2细胞中，Myocardin诱导miR-143/145和miR-133 a的表达，并增加SRF与这些基因的结合。这种myocardin介导的诱导减弱显性负Brg 1。在Brg 1-null SW 13细胞中，miR-143/145仅在Brg 1存在下被myocardin显著诱导，而miR-133不以Brg 1依赖性方式被myocardin诱导。染色质免疫沉淀分析表明，在Brg 1的存在下，心肌素增加SRF结合miR-143/145和miR-133 a基因座。总之，这些数据表明了一种机制，其中含有Brg 1的SWI/SNF复合物是心肌素诱导平滑肌细胞中miR-143/145表达所必需的。与此相反，miR-133的表达似乎是由Brg 1染色质重塑复合物在一个部分SRF依赖性，虽然很大程度上心肌蛋白的独立方式。SWI/SNF介导的染色质重塑通过影响蛋白质编码基因和microRNA的表达来调节平滑肌的表型。
MicroRNAs are involved in phenotypic switching of smooth muscle cells (SMCs). Brg1-containing SWI/SNF chromatin-remodeling complexes also play an important role in controlling the phenotype of SMCs. We thus determined whether Brg1 influences the transcription of microRNAs in SMCs. Microarray and quantitative RT-PCR analysis of smooth muscle from mice harboring smooth muscle-specific deletion of Brg1 revealed altered expression of several microRNAs, including miRs-143/145 and miR-133. Ablation of Brg1 in SMCs in vitro either by expression of dominant negative Brg1 or Brg1 knock-out attenuated miRs-143/145 expression. Knockdown of serum response factor (SRF) in SMCs significantly reduced the expression levels of miRs-143/145 and miR-133, whereas knockdown of myocardin only attenuated miRs-143/145 expression. Myocardin induced expression of miRs-143/145 and miR-133a and increased SRF binding to these genes in 10T1/2 cells. This myocardin-mediated induction was attenuated by dominant negative Brg1. In Brg1-null SW13 cells, miRs-143/145 were dramatically induced by myocardin only in the presence of Brg1, whereas miR-133 was not induced by myocardin in a Brg1-dependent manner. Chromatin immunoprecipitation assays demonstrated that in the presence of Brg1, myocardin increased SRF binding to both the miRs-143/145 and miR-133a loci. Together, these data suggest a mechanism in which Brg1-containing SWI/SNF complexes are required for myocardin to induce expression of miRs-143/145 in smooth muscle cells. In contrast, miR-133 expression appears to be regulated by Brg1-containing chromatin remodeling complexes in a partially SRF-dependent, although largely myocardin-independent manner. SWI/SNF-mediated chromatin remodeling thus regulates the phenotype of smooth muscle by affecting expression of protein-coding genes and microRNAs.