The Brm gene suppressed at the post-transcriptional level in various human cell lines is inducible by transient HDAC inhibitor treatment, which exhibits antioncogenic potential
The Brm gene suppressed at the post-transcriptional level in various human cell lines is inducible by transient HDAC inhibitor treatment, which exhibits antioncogenic potential
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DOI：
10.1038/sj.onc.1208716
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发表时间：
2005-08-18
期刊：
影响因子：
8
通讯作者：
Iba, H
中科院分区：
文献类型：
--
作者：
Yamamichi, N;Yamamichi-Nishina, M;Iba, H
哺乳动物的SWI/SNF染色质重塑复合体由10多个蛋白质亚基组成，在表观遗传调控中发挥重要作用。每个复合体包括一个BRG1或BRM分子作为催化亚单位。我们先前报道，BRM的缺失，而不是BRG1的缺失，会导致基于小鼠白血病病毒的逆转录病毒载体的转录基因沉默。为了了解BRM蛋白的生物学功能和生物发生机制，我们研究了来自不同人类肿瘤的七个不产生BRM蛋白的细胞系。在这里，我们发现这些BRM缺陷细胞系通过核连续转录实验检测到BRM基因的有效转录，而通过反转录-聚合酶c-am反应分析检测不到BRM mRNA和BRM hnRNA。这些结果表明，BRM的表达在转录后水平、通过初级转录本的加工和运输或通过成熟BRM mRNA的稳定而被强烈而迅速地抑制。用HDAC抑制剂短暂处理这些细胞系，这种抑制作用可能是通过间接机制减弱的。重要的是，在去除HDAC抑制剂后，所有处理的细胞都显示出长时间的BRM表达诱导，并获得了维持逆转录病毒基因表达的能力。这些结果表明，这些BRM缺陷的人类肿瘤细胞株携带有功能的BRM基因。用HDAC抑制剂处理或将外源BRM引入BRM缺失的细胞系显著降低致癌潜力，通过软琼脂中的克隆形成活性或对胶原凝胶的侵袭来评估，表明BRM与BRG1一样，参与了肿瘤抑制。
The mammalian SWI/SNF chromatin remodeling complex is composed of more than 10 protein subunits, and plays important roles in epigenetic regulation. Each complex includes a single BRG1 or Brm molecule as the catalytic subunit. We previously reported that loss of Brm, but not BRG1, causes transcriptional gene silencing of murine leukemia virus-based retrovirus vectors. To understand the biological function and biogenesis of Brm protein, we examined seven cell lines derived from various human tumors that do not produce Brm protein. We show here that these Brm-deficient cell lines transcribe the Brm genes efficiently as detected by nuclear run-on transcription assay, whereas Brm mRNA and Brm hnRNA were undetectable by reverse transcription-polymerase c am reaction analysis. These results indicate that expression of Brm is strongly and promptly suppressed at the posttranscriptional level, through processing and transport of the primary transcript or through stability of mature Brm mRNA. This suppression was attenuated by transient treatment of these cell tines with HDAC inhibitors probably through indirect mechanism. Importantly, all of the treated cells showed prolonged induction of Brm expression after the removal of HDAC inhibitors, and acquired the ability to maintain retroviral gene expression. These results indicate that these Brm-deficient human tumor cell tines carry a functional Brm gene. Treatment with HDAC inhibitors or introduction of exogenous Brm into Brm-deficient cell lines significantly reduced the oncogenic potential as assessed by colony-forming activity in soft agar or invasion into collagen gel, indicating that, like BRG1, Brm is involved in tumor suppression.