Department of Cellular and Integrative Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
J Biol Chem. 2013 Mar 1;288(9):6397-408. doi: 10.1074/jbc.M112.409474. Epub 2013 Jan 20.
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.
微小 RNA 参与平滑肌细胞 (SMCs) 的表型转换。BRG1 包含的 SWI/SNF 染色质重塑复合物在控制 SMC 表型方面也起着重要作用。因此，我们确定 BRG1 是否影响 SMC 中 microRNAs 的转录。对携带平滑肌特异性 BRG1 缺失的小鼠平滑肌进行 microarray 和定量 RT-PCR 分析，揭示了几个 microRNAs 的表达发生改变，包括 miR-143/145 和 miR-133。在体外通过表达显性负性 BRG1 或 BRG1 敲除，BRG1 在 SMC 中的缺失减弱了 miR-143/145 的表达。在 SMC 中敲低血清反应因子 (SRF) 显著降低了 miR-143/145 和 miR-133 的表达水平，而仅敲低心肌肌球蛋白则减弱了 miR-143/145 的表达。心肌肌球蛋白诱导 10T1/2 细胞中 miR-143/145 和 miR-133a 的表达，并增加这些基因的 SRF 结合。这种心肌肌球蛋白介导的诱导作用被显性负性 BRG1 减弱。在 BRG1 缺失的 SW13 细胞中，仅在存在 BRG1 的情况下，心肌肌球蛋白就可显著诱导 miR-143/145，而 miR-133 则不以 BRG1 依赖的方式被心肌肌球蛋白诱导。染色质免疫沉淀分析表明，在存在 BRG1 的情况下，心肌肌球蛋白增加了 SRF 与 miR-143/145 和 miR-133a 基因座的结合。总之，这些数据表明了一种机制，即含有 BRG1 的 SWI/SNF 复合物是心肌肌球蛋白诱导平滑肌细胞中 miR-143/145 表达所必需的。相比之下，miR-133 的表达似乎受含有 BRG1 的染色质重塑复合物调控，部分依赖于 SRF，但在很大程度上不依赖于心肌肌球蛋白。SWI/SNF 介导的染色质重塑通过影响蛋白质编码基因和 microRNAs 的表达来调节平滑肌的表型。
