BRF1泛素化修饰调控肿瘤细胞RNA聚合酶III活性的作用及机制研究

Numerous studies have demonstrated that compared to normal cells, tumor cells exhibit enhanced RNA polymerase III transcription. It has been shown that enhanced RNA polymerase III transcription is required for oncogenic transformation of normal cells, suggesting that enhanced RNA polymerase III transcription in cancer cells is actively involved in the tumor initiation and progression. However, the molecular mechanisms underlying the dysregulation of RNA polymerase III in cancer cells remain largely unclear. Our research aims to address this issue. Our preliminary data show that as an essential initiation factor for RNA polymerase III transcription, BRF1 is subjected to polyubiquitination. In addition, RNF12 is identified as a novel E3 ubiquitin ligase to mediate the polyubiquitination of BRF1. More importantly, RNF12 is capable of regulating RNA polymerase III transcription. In this study, we will further investigate the molecular mechanism whereby RNF12-mediated polyubiquitination of BRF1 regulates RNA polymerase III transcription in cancer cells. We will also evaluate the possible role of RNF12-mediated BRF1 polyubiquitination in tumor initiation and progression. This study will generate novel insights into the mechanisms of RNA polymerase III dysregulation in cancer cells. This may also implicate RNF12 as a novel potential therapeutic target for the treatment of cancer.

与正常细胞相比，肿瘤细胞中的RNA聚合酶III高度活化，并且其活性的增强被证实在正常细胞发生致癌性转化过程中发挥了关键的作用，这表明肿瘤细胞中RNA聚合酶III活性的增强主动地促进了肿瘤的发生发展，然而目前关于RNA聚合酶III在肿瘤细胞中活性增强的机制仍不明确。本项目以此为研究切入点，我们的前期研究结果表明，RNA聚合酶III特异性的转录起始因子BRF1在体内发生多聚泛素化修饰；RNF12能够结合BRF1，并作为E3泛素连接酶介导BRF1的多聚泛素化过程；并且RNF12具有调控肿瘤细胞RNA聚合酶III活性的功能。本项目将在已有的工作基础上，进一步深入研究RNF12介导的BRF1多聚泛素化调控肿瘤细胞RNA聚合酶III活性的作用及机制；同时也将研究其在肿瘤发生发展中的作用。这将从全新的角度揭示肿瘤细胞中RNA聚合酶III异常活化的分子机制，并可能为肿瘤治疗提供新的潜在靶点。

与正常细胞相比，肿瘤细胞中的RNA聚合酶III高度活化，并且其活性的增强被证实在正常细胞发生致癌性转化过程中发挥了关键的作用，这表明肿瘤细胞中RNA聚合酶III活性的增强主动地促进了肿瘤的发生发展，然而目前关于RNA聚合酶III在肿瘤细胞中活性增强的机制仍不明确。本项目以RNA聚合酶III特异性的转录起始因子BRF1为研究切入点，我们的研究发现，BRF1在体内能够发生多聚泛素化修饰，这一过程是由BRF1特异性的泛素连接酶RNF12介导的。RNF12能够结合BRF1、并催化BRF1形成Lys27和Lys33依赖的多聚泛素链。RNF12通过催化BRF1发生泛素化修饰，进而抑制BRF1定位到RNA聚合酶III靶基因的启动子区域。更为重要的是，在功能上，RNF12能够通过调节BRF1的多聚泛素化，进而抑制RNA聚合酶III的活性及肿瘤细胞的恶性增殖过程。这些结果揭示了一种RNA聚合酶III活性调控的新机制，并表明RNF12在肿瘤中的低表达可能促进了肿瘤细胞中RNA聚合酶III的活化；同时也暗示RNF12可能作为一个新的干预肿瘤的潜在分子靶标。在本项目的大力资助下，项目负责人以通讯作者的身份在PNAS、EMBO Reports和JBC等国际主流期刊上发表SCI学术论文5篇。