Cancer metastasis-associated protein 1 localizes to the nucleolus and regulates pre-rRNA synthesis in cancer cells
Cancer metastasis-associated protein 1 localizes to the nucleolus and regulates pre-rRNA synthesis in cancer cells
复制标题
癌症转移相关蛋白 1 定位于核仁并调节癌细胞中前 rRNA 的合成
DOI：
10.1002/jcb.29837
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发表时间：
2020-08-12
影响因子：
4
通讯作者：
Qian，Haili
中科院分区：
文献类型：
--
作者：
Liu，Jian;Li，Chunxiao;Qian，Haili
转移相关蛋白1(MTA1)是核小体重构和组蛋白去乙酰化酶(NuRD)复合体的重要组成部分。MTA1具有多种生物学功能，与人类癌症的恶性特性密切相关；然而，MTA1在细胞中的作用机制和亚细胞定位尚不清楚。一些初步研究表明，核仁中不存在MTA1；然而，最近发现核仁中存在几个NuRD成分，它们在那里调节胸前RNA(Pre-rRNA)转录。在本研究中，我们证明了MTA1确实定位于核仁并调节前rRNA转录，这与最近关于NuRD的报道一致。为了确定MTA1是否存在于核仁中，我们使用了以下互补的分子方法：免疫荧光、GFP标记跟踪、免疫电子显微镜和免疫沉淀(IP)。为了研究MTA1在rRNA合成中的作用，我们进行了定量聚合酶链式反应分析。我们发现，内源性和外源性MTA1都表现出明显的颗粒状核仁亚细胞定位。MTA1与两种主要的核仁蛋白--核仁蛋白和核磷蛋白相互作用。免疫荧光共定位分析表明，MTA1定位于核仁的纤维蛋白缺陷区，Co-IP实验表明MTA1与纤维蛋白没有相互作用；此外，在MTA1相互作用组中没有发现纤维蛋白。功能丧失和功能获得的研究表明，MTA1促进癌细胞中的前rRNA转录。总的来说，我们的数据确定MTA1是一种新的核仁蛋白，癌细胞中前rRNA转录的激活可能是MTA1促进恶性肿瘤的另一种机制。
Metastasis‐associated protein 1 (MTA1) is a critical component of the nucleosome remodeling and histone deacetylase (NuRD) complex. MTA1 has several biological functions, and it is closely associated with the malignant properties of human cancers; however, the mechanisms and subcellular localization of MTA1 in cells remain unclear. Some initial studies indicated that MTA1 was absent from the nucleolus; however, several NuRD components were recently found to be present in the nucleolus, where they regulate preribosomal RNA (pre‐rRNA) transcription. In this study, we demonstrated that MTA1 is definitely localized to the nucleolus and regulates pre‐rRNA transcription, which is consistent with the recent reports on NuRD. To determine if MTA1 was present in the nucleolus, we utilized the following complementary molecular approaches: immunofluorescence, GFP‐tag tracking, immunoelectron microscopy, and immunoprecipitation (IP). To examine the role of MTA1 in rRNA synthesis, we performed quantitative polymerase chain reaction analysis. We revealed that both endogenous and exogenous MTA1 showed apparent granule‐like nucleolar subcellular localization. MTA1 interacts with two major resident nucleolar proteins, nucleolin and nucleophosmin. Immunofluorescent colocalization analyses showed that MTA1 localizes to the fibrillarin‐deficient regions of the nucleolus, and Co‐IP experiments indicated that there was no interaction between MTA1 and fibrillarin; further, fibrillarin was not identified in the MTA1 interactome. Loss‐ and gain‐of‐function studies indicated that MTA1 promotes pre‐rRNA transcription in cancer cells. Collectively, our data identify MTA1 as a novel nucleolar protein, and activation of pre‐rRNA transcription in cancer cells may be an alternative mechanism by which MTA1 promotes malignancies.