Dissection of the feedback inhibition of c-Myc by L11

描述(申请人提供)：c-Myc癌蛋白是一个非常感兴趣的细胞靶标，因为它的适当生理水平对于正常的细胞生长和增殖是必不可少的，而它的非调控过表达与许多人类癌症密切相关。因此，必须在细胞内严格控制c-Myc的水平和活性。为了了解c-Myc的调控，我最近发现核糖体大亚基的一种成分核糖体蛋白L11可以抑制c-Myc的反式激活活性和诱导细胞增殖。由于L11是由c-Myc转录诱导的，这些结果导致了一个重要的假设，即L11可能是c-Myc的关键自我调节反馈抑制因子。我目前的研究重点是通过进一步研究L11-c-Myc蛋白-蛋白相互作用、L11蛋白-c-myc mRNA相互作用以及L11对c-Myc促进的核糖体生物发生的抑制作用来了解这种L11-c-Myc反馈抑制作用。 我在独立阶段应用这项技术的广泛、长期的目标是研究L11如何抑制c-Myc功能，以及L11是否抑制c-Myc在细胞中的转化活性和体内的致癌活性。为了研究L11抑制c-Myc活性的机制，我将分析L11是否隐藏了其靶基因启动子上的c-Myc反式激活结构域；2)为了研究L11是否通过microRNA引导的途径调节c-myc的mRNA水平和翻译，我将研究L11是否通过RNA干扰沉默复合体(RISC)与c-myc mRNA的3‘-UTR结合来降解c-myc mRNA和/或沉默其翻译；3)为了探讨L11对c-Myc的抑制作用的生理学意义，我将确定L11-c-Myc环是否在正常细胞生长反应和某些类型的细胞应激反应中发挥作用，以及L11是否抑制c-Myc诱导的细胞转化和小鼠肿瘤形成。 通过生物化学、细胞和分子生物学以及遗传学方法实现这些目标，将证明L11通过抑制c-Myc而具有一种新的肿瘤抑制功能。由于阻断c-Myc的表达可导致多个组织中c-Myc诱导的肿瘤的消退，因此L11‘S抑制c-Myc的机制研究结果将为开发针对癌症患者c-Myc的抗肿瘤药物提供有用的信息。

DESCRIPTION (provided by applicant): The c-Myc oncoprotein is a cellular target of great interest because its proper physiological level is essential for normal cell growth and proliferation, while its deregulated overexpression is closely related to many human cancers. Thus c-Myc level and activity must be tightly controlled in cells. In an attempt to understand the regulation of c-Myc, I have recently identified that ribosomal protein L11, a component of the large subunit of the ribosome, inhibits c-Myc transactivation activity and induction of cell proliferation. As L11 is transcriptionally induced by c-Myc, these results lead to an important hypothesis that L11 may act as a critical auto-regulatory feedback inhibitor of c-Myc. My current research focuses on understanding this L11-c-Myc feedback inhibition by further characterizing L11-c-Myc protein-protein interaction, L11 protein-c-myc mRNA interaction, and the inhibitory effect of L11 on c-Myc-enhanced ribosomal biogenesis. My broad, long-term objectives of this application in the independent phase are to study how L11 inhibits c-Myc function and whether L11 suppresses c-Myc's transformation activity in cells and oncogenic activity in vivo. Three specific aims are proposed: 1) To investigate the mechanisms underlying the inhibitory role of L11 on c-Myc activity, I will analyze whether L11 conceals c-Myc transactivation domain on its target gene promoters; 2) To investigate whether L11 regulates c-myc mRNA level and translation through microRNA-guided pathways, I will investigate whether L11 binds to 3'-UTR of c-myc mRNA with RNA interference silencing complex (RISC) to degrade c-myc mRNA and/or silence its translation; 3) To investigate the physiological significance of the inhibitory effect of L11 on c-Myc, I will determine whether L11-c-Myc loop plays a role in normal cellular growth response and also in response to certain types of cellular stress, and whether L11 suppresses c-Myc-induced transformation in cells and tumor formation in mice. Achieving these aims from this project using biochemical, cellular and molecular biological, and genetic approaches would demonstrate a novel tumor suppressive function of L11 by inhibiting c-Myc. Since ablating c-Myc expression leads to regression of c-Myc-induced tumors in multiple tissues, results from the mechanistic studies on L11's inhibitory effect on c-Myc would offer useful information for developing antitumor drugs that target c-Myc in cancer patients.