Functions of mir-34 microRNAs in the p53 tumor suppressor pathway

描述（申请人提供）：p53是最常突变的肿瘤抑制因子，被认为是基因组的守护者。过去三十年的深入研究已经将p53置于一个复杂分子网络的中心，该网络调节对癌症相关应激信号的多种生理反应。在以前的研究中，p53网络的组成部分仅由蛋白质编码基因组成，包括上游作用于调节p53活性的基因，下游作用于介导p53效应的基因，以及形成调节p53活性动力学的调节反馈环的基因。我们小组和其他人最近的研究已经确定了一个家族的microRNAs（miRNAs），mir-34 a，B和c，作为p53真正的转录靶点。这些发现首次揭示了蛋白质和非编码RNA在这一最重要的肿瘤抑制途径中的相互作用。miRNAs是一类新型的小的、调节性的非编码RNA，其介导大量靶mRNA的转录后基因沉默。mir-34 miRNAs的异位表达模拟了p53在生长停滞和凋亡中的生物学作用，可能是通过它们抑制促增殖和促存活基因表达的能力。鉴于这些初步发现，我们假设内源性mir-34 miRNAs是介导许多p53下游效应的关键效应子，并且mir-34的功能对肿瘤发生和肿瘤维持具有深远影响。利用细胞培养研究和小鼠遗传学研究，我们建议确定mir-34 miRNAs是否介导p53诱导的生长停滞和凋亡，以及mir-34 miRNAs在多大程度上有助于p53介导的肿瘤抑制和肿瘤消退。公共卫生相关性：p53是已确定的最重要的肿瘤抑制因子之一，正如其在人类癌症中的频繁突变所示。响应于各种癌症相关的应激信号，p53可以在细胞核内迅速积累，分别激活和抑制许多靶点的转录。通过这些下游效应物的功能，p53发挥抗增殖作用，诱导细胞凋亡，阻断血管生成和促进DNA修复，这些共同防止肿瘤形成并排除肿瘤维持。大量的文献致力于调节p53激活或介导p53效应的关键分子事件。然而，迄今为止，大多数p53研究都集中在p53通路中的蛋白质组分上，不幸的是，这些研究忽略了非编码RNA，特别是microRNA（miRNAs）的潜在影响。miRNAs在基因组中表现出丰富的表达，并具有很强的基因调控和信号转导能力。近年来，miRNAs作为一类小分子调控RNA，参与了几乎所有与恶性转化相关的细胞改变，包括增殖、复制能力、凋亡、转移和血管生成。很明显，这个基因家族紧密地整合到通常在转化过程中被破坏的调控过程中。本文提出的研究源于我们最初的观察，即mir-34家族miRNAs是p53介导的转录的直接靶点，并且强制mir-34表达概括了p53的一些功能。我们提出的研究旨在阐明mir-34 miRNAs在p53肿瘤抑制网络中的功能。将这些miRNA组分放入众所周知的p53肿瘤抑制网络中将有助于阐明p53通路的分子基础和分子电路，也可能为我们探索miRNA与癌基因和肿瘤抑制网络之间的功能性串扰提供一个范例。鉴于miRNA的小尺寸，这些小RNA分子可以容易地作为治疗剂在体内递送。miRNAs具有开发成为诊断标志物或治疗剂的巨大潜力。阐明mir-34家族在p53信号通路中的作用，有助于评价该家族的治疗潜力，为临床肿瘤的治疗和诊断提供参考。

DESCRIPTION (provided by applicant): p53, the most frequently mutated tumor suppressor, is regarded as the guardian of the genome. Intensive studies over the past three decades have placed p53 in the center of a complex molecular network regulating diverse physiological responses to cancer- related stress signals. In previous studies, the components of the p53 network solely consist of protein coding genes, including those acting upstream to regulate p53 activity, those functioning downstream to mediate p53 effects, and those forming a regulatory feedback loop regulating the dynamics of the p53 activity. Recent studies from our group and others have identified a family microRNAs (miRNAs), mir-34a, b and c, as bona fide transcriptional targets of p53. These findings, for the first time, revealed the interplay between proteins and non-coding RNAs in this most important tumor suppressor pathway. miRNAs are a novel class of small, regulatory non-coding RNAs that mediate post-transcriptional gene silencing of a large number of target mRNAs. The ectopic expression of mir-34 miRNAs mimics the biological effects of p53 in growth arrest and apoptosis, possibly through their ability to dampen the expression of pro-proliferation and pro-survival genes. Given these preliminary findings, we hypothesize that the endogenous mir-34 miRNAs are key effectors to mediate many of the p53 downstream effects, and that the functions of mir-34 have profound impacts on tumorigenesis and tumor maintenance. Using cell culture studies and mouse genetic studies, we propose to determine whether mir-34 miRNAs mediate p53 induced growth arrest and apoptosis, and to what extent mir-34 miRNAs contribute to p53 mediated tumor suppression and tumor regression. PUBLIC HEALTH RELEVANCE: p53 is among the most important tumor suppressors identified, as indicated by its frequent mutations in human cancers. In response to a variety of cancer related stress signals, p53 can quickly accumulate inside the nucleus to activate and repress transcription of a number of targets, respectively. Through the functions of these downstream effectors, p53 exert anti-proliferative effects, induce apoptosis, block angiogenesis and promote DNA repair, which collectively prevent tumor formation and preclude tumor maintenance. A huge body of literature has been devoted to the key molecular events that regulate p53 activation or mediate p53 effects. However, most p53 research so far has focused on the protein components in the p53 pathway, which, unfortunately, neglected the potential impacts from non-coding RNAs, in particular, microRNAs (miRNAs). miRNAs exhibit abundance in the genome and possess great capacity for gene regulation and signaling transduction. In recent years, miRNAs, as a class of small regulatory RNAs, have emerged to be involved in nearly all of the essential cellular alterations associated with malignant transformation, including proliferation, replication potential, apoptosis, metastasis, and angiogenesis. It is clear that this family of genes is intimately integrated into the regulatory processes that are normally disrupted during transformation. Studies proposed here stem from our initial observations that mir-34 family miRNAs are direct targets of the p53 mediated transcription, and that enforced mir-34 expression recapitulate some of p53 functions. Our proposed studies presented here aim to elucidate the functions of mir-34 miRNAs in the p53 tumor suppressor network. The placement of these miRNA components into the well known p53 tumor suppressor network will help to elucidate the molecular basis and the molecular circuitry of the p53 pathway, and may also provide a paradigm for us to explore the functional cross talk between miRNAs and the oncogene and tumor suppressor network in general. Given the small size of miRNAs, these small RNA molecules can be easily delivered in vivo as a therapeutic agent. miRNAs have substantial potentials to be developed into diagnostic markers or therapeutical agents. Elucidating the roles of mir-34 family of miRNAs in the p53 pathway may also help us to evaluate the therapeutical potentials of this miRNA family, and may contribute to the cancer treatment and diagnosis in clinics.