Interaction between RNA interference and RNA editing pathways

描述（由申请人提供）：一种类型的RNA编辑涉及通过作用于RNA的腺苷脱氨酶（阿达尔）的作用将双链RNA（dsRNA）中的腺苷残基转化为肌苷。在人类和啮齿类动物中已鉴定出三个阿达尔基因家族成员（ADAR 1 -3）。当A1 RNA编辑发生在编码序列内时，可以导致不直接由基因组编码的蛋白质的合成，如谷氨酸受体（GluR）离子通道和5-HT 2C血清素受体的转录物所证明的。然而，A1编辑的最常见靶标是非编码RNA，其含有位于内含子和3'UTR内的重复元件如Alu和LINE的反向重复序列。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A1 RNA编辑的生物学意义。在过去的17年里，这项资助使我们能够克隆ADAR 1，这是阿达尔基因家族的第一个成员。这反过来又导致了ADAR 2和ADAR 3的鉴定和克隆。此外，我们已经在小鼠中产生了ADAR 1-/-突变，导致广泛的细胞凋亡和随后的胚胎致死表型。我们的研究结果表明，ADAR 1通过编辑目前未知的靶dsRNA对许多组织的存活至关重要。在目前的资助期间，我们发现ADAR 1和ADAR 2都编辑某些miRNA前体dsRNA（pri-miRNAs）的特定腺苷残基。pri-miRNA的编辑导致抑制其加工或编辑的成熟miRNA的表达，所述成熟miRNA沉默与未编辑的miRNA靶向的基因不同的基因。我们的发现揭示了A1 RNA编辑在miRNA介导的基因沉默中的先前未知的作用。最后，我们的初步结果表明，ADAR 1与某些miRNA诱导的沉默复合物（miRISC）成员蛋白。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，在本申请所体现的拟议工作中，我们将把我们的研究努力集中在这种RNAi和RNA编辑的相互作用上作为我们的主要推力。具体地，我们将确定：1）在胚胎发育期间编辑的某些miRNA对于调节细胞凋亡的意义; 2）重复非编码RNA的A1编辑对于控制内源siRNA（esiRNA）表达的意义;和3）ADAR 1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，miRNAs的突变和错误表达与各种人类癌症相关。某些miRNAs可以作为肿瘤抑制因子和癌基因发挥作用。因此，目前研究miRNA和siRNA的A&I编辑效果的拨款提案与癌症生物学相关。我们的研究也集中在细胞凋亡，这是高度相关的许多人类疾病，包括癌症。

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.