Mda-5: Novel Apoptosis Inducing Gene

说明(申请人提供)：干扰素(干扰素)具有广泛的细胞类型特异性作用，包括抑制生长、抗病毒活性、调节分化、诱导或抑制细胞程序性死亡(凋亡)以及调节免疫系统基因和表达。I型干扰素包括干扰素-α和干扰素-β，其生长抑制和/或凋亡作用是通过蛋白激酶R、2‘-5’寡腺苷合成酶和附加的干扰素诱导的核糖核酸酶介导的。RNA解旋酶由一系列蛋白质组成，参与RNA新陈代谢的各种过程，包括降解、翻译和编辑。干扰素诱导的RNA解旋酶在介导细胞生理变化中的相关性尚不清楚。消减杂交证实黑色素瘤分化相关基因-5(MDA-5)是一个新的干扰素-β诱导基因，其编码蛋白含有半胱氨酸天冬氨酸酶招募结构域(CARD)和RNA解旋酶基序。纯化的MDA-5融合蛋白具有dsRNA依赖的ATPase活性，由于同时存在CARD和RNA解旋酶结构域，因此是RNA解旋酶基因家族中一个独特的成员。此外，MDA-5的RNA解旋酶基序与生长抑制蛋白和/或RNaseIII解旋酶蛋白有某些共同的特性。这些发现，包括哺乳动物细胞中丙二醛-5的生长抑制活性，支持了丙二醛-5是一种独特的RNA解旋酶的假设，该酶参与了干扰素诱导的生长抑制/凋亡的RNA代谢。由于RNA代谢在细胞凋亡过程中的潜在参与是独一无二的，对MDA-5的分析可能代表一个首次连接这些重要过程的分子，为确定凋亡RNA代谢和干扰素的作用提供了一个非同寻常的机会。这些信息可能被证明与理解干扰素抵抗病毒攻击的细胞防御机制以及干扰素在介导抗肿瘤反应中的作用有关。实验将确定MDA-5在干扰素诱导的生长抑制和/或凋亡中的生物学作用，寻找参与介导MDA-5作用的潜在蛋白质伙伴，并鉴定MDA-5的RNA底物和表征MDA-5的ATPase活性。了解MDA-5的功能可以提供对RNA的重要见解，具有新的凋亡处理潜力，定义治疗方法，界定感染性和发病机制。此外，基于其染色体位置2q24，本研究还可以阐明MDA-5在特定癌症病因中的潜在作用，并增强我们对致癌过程的认识。

DESCRIPTION (provided by applicant): Interferons (IFN) have broad cell-type specific effects, including growth inhibition, antiviral activity, modulation of differentiation, induction or inhibition of programmed cell death (apoptosis) and regulation of immune system genes and expression. The growth inhibitory and/or apoptotic effects of type I IFNs, which include IFN-alpha and IFN-beta, are mediated by protein kinase R, 2'-5' oligoadenylate syntase and additional IFN-inducible RNases. The RNA helicases comprise a family of proteins implicated in diverse processes of RNA metabolism, including degradation, translation and editing. The relevance of IFN-induced RNA helicases in mediating changes in cellular physiology is not understood. Subtraction hybridization identified melanoma differentiation associated gene-5 (mda-5) as a novel IFN-beta induced gene whose encoded protein contains a caspase recruitment domain (CARD) and RNA helicase motif. Purified MDA-5 fusion protein exhibits dsRNA-dependent ATPase activity and because of the presence of both CARD and RNA helicase domains represents a unique member of the RNA helicase gene family. Moreover, the RNA helicase motif of MDA-5 shares certain peculiarities with growth inhibitory and/or RNase III helicase proteins. These findings, including the growth suppressing activity of mda-5 in mammalian cells, support the hypothesis that MDA-5 is a unique RNA helicase involved in growth inhibitory/apoptotic RNA metabolism elicited by IFN treatment. Since a potential involvement of RNA metabolism in the apoptotic process is unique, analysis of MDA-5, which may represent a molecule that for the first time links these important processes, provides an extraordinary opportunity to define the role of apoptotic RNA metabolism and IFN action. This information could prove relevant in understanding the mechanism of cellular defense conferred by IFN against viral attack as well as the role of interferons in mediating antitumor responses. Experiments will be performed to define the biological role of mda-5 in IFN-induced growth inhibition and/or apoptosis, identify potential protein partners of MDA-5 involved in mediating mda-5 action, and identify RNA substrates of MDA-5 and characterize the ATPase activity of MDA-5. Understanding MDA-5 function could provide significant insights into RNA with novel apoptotic processing potential defining therapeutics delimiting infectivity and pathogenesis. Additionally, based on its chromosomal location, 2q24, the present studies could also shed light on a potential role of mda-5 in specific cancer etiologies as well as enhance our appreciation of the carcinogenic process.