The role of microRNA in oncogene-induced senescence and cancer development

描述（申请人提供）：微小RNA（miRNA）是一类小的非编码RNA，通过翻译抑制和/或mRNA降解抑制蛋白质编码基因的表达。研究表明，miRNA通过参与包括癌症发展在内的广泛的生理和病理过程，作为细胞功能的全局调节剂。在遗传筛选中，我们发现miR-30，一种在癌症中经常过表达的miRNA，破坏了一种称为癌基因诱导衰老的关键肿瘤抑制机制。进一步的研究表明，miR-30通过直接靶向CHD 7（一种转录共激活因子）和TNRC 6A（一种对miRNA功能至关重要的RNA结合蛋白）破坏致癌ras诱导的衰老。在这项资助申请中，我们将研究CHD 7和TNRC 6A在miR-30介导的致癌ras诱导衰老旁路中的作用机制，并研究miR-30-CHD 7/TNRC 6A调节回路对体内癌症发展的影响。在目标1中，我们将研究CHD 7作为转录共激活因子诱导关键衰老效应子p16 INK 4A转录的假设，以及通过抑制CHD 7，miR-30抑制ras诱导的p16 INK 4A表达，从而抑制衰老诱导。提出了进行ChIP-seq分析的替代方法，以系统地鉴定参与衰老的CHD 7的其他直接转录靶点。在目标2中，将测试以下假设：通过抑制TNRC 6A，miR-30全面下调miRNA的功能，这反过来导致ras诱导的衰老的破坏。在目标3中，我们将使用miR-30转基因小鼠和小鼠癌症模型分析miR-30对体内衰老诱导和癌症发展的影响。此外，将在人类肿瘤样品中测定miR-30、CHD 7和TNRC 6A的表达水平，以确定miR-30通过抑制其直接靶点CHD 7和TNRC 6A而促进人类癌症发展。这项研究将为miR-30在癌基因诱导的衰老中的新功能提供机制性见解。通过对这些miR-30靶点的分析，我们将确定介导癌基因诱导的衰老和肿瘤抑制的新机制和新信号组分，这将为靶向细胞衰老的癌症治疗提供新的机会。

DESCRIPTION (provided by applicant): microRNA (miRNA) is a class of small non-coding RNAs that suppress the expression of protein-encoding genes via translational repression and/or mRNA degradation. Studies indicate that miRNAs act as global regulators of cellular functions, through their involvement in a wide range of physiological and pathological processes including cancer development. In a genetic screen, we found that miR-30, a miRNA frequently overexpressed in cancer, disrupts a critical tumor suppressing mechanism called oncogene-induced senescence. Further studies demonstrated that miR-30 disrupts oncogenic ras-induced senescence by directly targeting CHD7, a transcriptional co-activator, and TNRC6A, an RNA-binding protein essential for miRNA functionality. In this grant application, we will investigate te mechanisms underlying the roles of CHD7 and TNRC6A in miR-30-mediated bypass of oncogenic ras-induced senescence, and examine the impact of the miR-30-CHD7/TNRC6A regulatory circuit on cancer development in vivo. In Aim 1, we will investigate the hypothesis that CHD7 acts as a transcriptional coactivator to induce the transcription of a key senescence effector p16INK4A, and that by suppressing CHD7, miR-30 inhibits ras-induced p16INK4A expression and hence senescence induction. Alternative approaches are proposed to perform ChIP-seq analysis to systematically identify additional direct transcriptional targets of CHD7 involved in senescence. In Aim 2, the hypothesis will be tested that by suppressing TNRC6A, miR-30 globally down-regulates the functionality of miRNAs, which in turn leads to disruption of ras-induced senescence. In Aim 3, we will analyze the effect of miR-30 on senescence induction and cancer development in vivo using miR-30 transgenic mice and a mouse cancer model. In addition, the expression levels of miR-30, CHD7 and TNRC6A will be determined in human tumor samples, in order to establish that miR-30 contributes to human cancer development by suppressing its direct targets CHD7 and TNRC6A. Studies proposed in this grant will provide mechanistic insights into the novel function of miR-30 in oncogene-induced senescence. Through analyses of these miR-30 targets, we will identify novel mechanisms and novel signaling components that mediate oncogene-induced senescence and tumor suppression, which will offer new opportunities for cancer therapies targeting cellular senescence.