RBR家族E3泛素连接酶RNF144A通过组蛋白及非组蛋白泛素化修饰通路抑制乳腺癌侵袭转移的机制研究

Distant metastasis to specific target organs accounts for approximate 90% of breast cancer-related deaths. Thus, elucidation of the underlying mechanism for breast cancer invasion and metastasis is one of the key scientific issues that need to be addressed urgently in the field of breast cancer research. Ring finger protein 144A (RNF144A) is a member of the ring-between-ring (RBR) family of E3 ubiquitin ligases that possess intrinsic E3 ubiquitin ligase activity. However, its biological functions and related molecular mechanisms in tumor development and progression are largely unknown. Recently, multiple lines of evidence from our preliminary experiments clearly show that RNF144A is a potential suppressor for breast cancer invasion and metastasis, but the underlying mechanisms remain to be investigated. In this study, we aimed to address the functional roles and the underlying mechanisms for RNF144A in breast cancer invasion and metastasis using a variety of experimental models and techniques. To this end, the key scientific questions to be answered in this project include what are the histone and non-histone substrates of RNF144A, how RNF144A regulates the ubiquitination of those substrates, and what is the function for RNF144A-mediated histone and non-histone protein ubiquitination pathway in the process of breast cancer invasion and metastasis. The expected findings from this project will reveal the function as well as the molecular mechanism of RNF144A protein in breast cancer invasion and metastasis, and provide a clue for discovering new methods and/or strategies for combating breast cancer invasion and metastasis.

远处靶器官转移是导致乳腺癌患者死亡的主要原因，因此阐明其分子机制是乳腺癌研究领域亟需解决的关键科学问题之一。RBR (Ring-Between-Ring) 结构域家族蛋白RNF144A具有E3泛素连接酶活性，但其在肿瘤发生发展中的作用及其机理目前知之甚少。我们前期研究结果显示，RNF144A是一个潜在乳腺癌侵袭转移抑制蛋白，但其分子机制尚不清楚。本研究拟在此基础上，采用多种实验模型和技术, 深入解析RNF144A在乳腺癌侵袭转移中的作用及其分子机制，包括系统性鉴定RNF144A的组蛋白及非组蛋白作用底物、阐明调控其底物泛素化修饰的分子机制、以及明确RNF144A介导的组蛋白及非组蛋白泛素化修饰通路在乳腺癌侵袭转移中的作用。本研究将为揭示乳腺癌侵袭转移的分子机制以及促进发现新的干预乳腺癌侵袭转移的药物靶标提供重要线索。

环指蛋白144A (RNF144A) 属于最近发现的RBR (Ring-between Ring) E3泛素连接酶家族成员，目前关于此蛋白的功能研究报道甚少，特别是其在肿瘤发生发展过程中的功能尚未见报道。我们发现：(1) RNF144A通过DNA甲基化表位沉默机制在乳腺癌细胞和组织中表达下调。(2) 功能实验证实RNF144A在体外抑制乳腺癌细胞的克隆形成、迁移与侵袭潜能，在体内抑制乳腺癌裸鼠原位移植瘤的生长和肺转移。机制研究发现RNF144A通过促进癌蛋白热休克70 kDa蛋白2 (HSPA2) 泛素化修饰和降解，从而消除HSPA2介导的致癌活性。与这些研究结果一致，临床数据也表明RNF44A表达的减少而HSPA2表达的增加与乳腺癌患者不良预后相关。(3) RNF144A可以通过其跨膜结构域与DNA修复酶PARP1结合并促进其泛素化修饰和降解，影响乳腺癌细胞对于PARP抑制剂的敏感性。同时我们还发现RNF144A分子也可以被PARP1分子下调，这样RNF144A与PARP1蛋白之间形成一个负反馈调节关系。 这些研究结果为揭示RNF144A蛋白在乳腺癌进展过程中的作用及分子机制、以及促进发现新的干预乳腺癌的潜在药物靶点提供重要的线索。