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

描述(申请人提供)：microRNA(MiRNA)是一类小的非编码RNA，通过翻译抑制和/或mRNA降解来抑制蛋白质编码基因的表达。研究表明，miRNAs通过参与包括癌症发生在内的广泛的生理和病理过程，发挥着细胞功能的全球调节作用。在基因筛查中，我们发现miR-30，一种经常在癌症中过度表达的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通过直接靶向转录共激活因子CHD7和对miRNA功能至关重要的RNA结合蛋白TNRC6A来干扰致癌ras诱导的衰老。在这项拨款申请中，我们将研究CHD7和TNRC6A在miR-30介导的绕过ras诱导的致癌衰老中的作用的TE机制，并检测miR-30-CHD7/TNRC6A调节电路在体内癌症发展中的影响。在目标1中，我们将研究CHD7作为转录辅助激活因子诱导关键衰老效应因子p16INK4A转录的假设，以及通过抑制CHD7，miR-30抑制ras诱导的p16INK4A表达，从而抑制衰老诱导。另一种方法是进行芯片序列分析，以系统地识别参与衰老的CHD7的其他直接转录靶点。在目标2中，将检验这一假设，即通过抑制TNRC6A，miR-30全局下调miRNAs的功能，从而导致中断ras诱导的衰老。在目标3中，我们将利用miR-30转基因小鼠和一个小鼠肿瘤模型来分析miR-30在体内诱导衰老和肿瘤发展的作用。此外，还将测定miR-30、CHD7和TNRC6A在人类肿瘤样本中的表达水平，以确定miR-30通过抑制其直接靶点CHD7和TNRC6A在人类癌症发展中的作用。这项资助中提议的研究将为miR-30在癌基因诱导的衰老中的新功能提供机制方面的见解。通过对miR-30靶点的分析，我们将发现介导癌基因诱导的衰老和肿瘤抑制的新机制和新的信号成分，这将为针对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.