Interaction between RNA interference and RNA editing pathways

描述（由申请人提供）：一种RNA编辑涉及通过作用于RNA的腺苷脱氨酶（ADAR）将双链RNA （dsRNA）中的腺苷残基转化为肌苷。已在人类和啮齿动物中鉴定出三个ADAR基因家族成员（ADAR1-3）。当编码序列中发生RNA编辑时，可以合成非直接由基因组编码的蛋白质，如谷氨酸受体（GluR）离子通道和5-HT2C 5-羟色胺受体的转录本。然而，最常见的a1编辑目标是非编码rna，这些rna包含位于内含子和3' utr内的重复元件的反向重复，如Alu和LINE。非编码、重复RNA编辑的生物学意义在很大程度上是未知的。该项目的总体目标是更好地理解RNA编辑的生物学意义。在过去的17年里，这笔拨款使我们能够克隆ADAR1，这是ADAR基因家族中第一个确定的成员。这反过来又导致了ADAR2和ADAR3的鉴定和克隆。此外，我们在小鼠中创建了ADAR1-/-突变，导致广泛的细胞凋亡和随之而来的胚胎致死表型。我们的研究结果表明，通过编辑一个目前未知的靶dsRNA， ADAR1对许多组织的存活至关重要。在目前的资助期内，我们发现ADAR1和ADAR2都可以编辑某些miRNA前体dsRNAs （pri-miRNAs）的特异性腺苷残基。对pri- mirna的编辑导致其加工或编辑成熟mirna的表达受到抑制，从而沉默与未编辑mirna靶向的基因不同的基因。我们的发现揭示了先前未知的RNA编辑在mirna介导的基因沉默中的作用。最后，我们的初步结果表明ADAR1与某些mirna诱导沉默复合体（miRISC）成员蛋白相关。因此，我们的研究强烈表明，RNAi和RNA编辑途径在哺乳动物细胞中相互作用。因此，在本申请中所体现的拟议工作中，我们将把我们的研究重点放在RNAi和RNA编辑的相互作用上。具体来说，我们将确定：1)在胚胎发育过程中被编辑的某些mirna对细胞凋亡的调控意义；2)重复非编码rna的I编辑对控制内源性siRNA （esiRNA）表达的意义；3) ADAR1与miRISC成员蛋白相互作用的意义。公共卫生相关性：最近的研究表明，mirna的突变和错误表达与各种人类癌症相关。某些mirna可以作为肿瘤抑制因子和癌基因。因此，目前研究A&I编辑miRNAs和sirna的效果的拨款提案与癌症生物学相关。我们的研究重点还包括细胞凋亡，它与包括癌症在内的许多人类疾病密切相关。

DESCRIPTION (provided by applicant): One type of RNA editing involves the conversion of adenosine residues into inosine in double-stranded RNA (dsRNA) through the action of adenosine deaminase acting on RNA (ADAR). Three ADAR gene family members (ADAR1-3) have been identified in humans and rodents. When A I RNA editing occurs within a coding sequence, synthesis of proteins not directly encoded by the genome can result, as demonstrated with transcripts of glutamate receptor (GluR) ion channels and 5-HT2C serotonin receptors. However, the most common targets for A I editing are non-coding RNAs that contain inverted repeats of repetitive elements such as Alu and LINE located within introns and 3' UTRs. The biological significance of non-coding, repetitive RNA editing is largely unknown. The overall goal of this project is to better understand the biological significance of A I RNA editing. During the past 17 years, this grant has enabled us to clone ADAR1, the first identified member of the ADAR gene family. This in turn has led to the identification and cloning of ADAR2 and ADAR3. Furthermore, we have created an ADAR1-/- mutation in mice that causes widespread apoptosis and consequent embryonic lethal phenotypes. Our results suggest that ADAR1 is critically important for survival of numerous tissues by editing a currently unknown target dsRNA(s). During the current grant support period, we found that both ADAR1 and ADAR2 edit specific adenosine residues of certain miRNA precursor dsRNAs (pri-miRNAs). Editing of pri- miRNAs results in inhibition of their processing or expression of edited mature miRNAs that silence genes different from those targeted by unedited miRNAs. Our findings revealed a previously unknown role for A I RNA editing in miRNA-mediated gene silencing. Finally, our preliminary results indicate that ADAR1 associates with certain miRNA-induced silencing complex (miRISC) member proteins. Thus, our studies strongly indicate that the RNAi and RNA editing pathways interact in mammalian cells. Therefore, in the proposed work embodies in this application, we will focus our research efforts on this RNAi and RNA editing interaction as our main thrust. Specifically, we will determine: 1) the significance of certain miRNAs that are edited during embryonic development for regulation of apoptosis; 2) the significance of A I editing of repetitive non-coding RNAs for control of endogenous siRNA (esiRNA) expression; and 3) the significance of ADAR1 interaction with the miRISC member proteins. PUBLIC HEALTH RELEVANCE: Recent studies indicate that mutations and mis-expression of miRNAs correlate with various human cancers. Certain miRNAs can function as tumor suppressors and oncogenes. Thus, the current grant proposal to investigate the effect of A&I editing of miRNAs and siRNAs has relevance to cancer biology. Our research focuses also on apoptosis, which is highly relevant to many human diseases including cancer.