Loss of mtSIRT3, Decreased MnSOD Activity, and IR Induced Genomic Instability

描述（由申请人提供）：核基因组不稳定是癌症的一个标志，被认为是肿瘤发生的早期事件，包括偶然暴露或继发于治疗的红外诱导的恶性肿瘤。哺乳动物细胞含有保真蛋白，似乎可以保护动物免受内源性和外源性的基因毒性应激，包括电离辐射（IR）诱导的基因组不稳定性。这个想法是基于生物学的一个基本范式：哺乳动物细胞含有保真蛋白，可以识别特定的条件，包括细胞损伤，并随后启动信号级联，维持细胞的稳态平衡。此外，这些保真度蛋白的功能丧失或基因突变已被证明会产生肿瘤允许细胞表型，这表明这些蛋白也具有肿瘤抑制因子（TS）的功能。我们实验室的初步数据表明SIRT3是一种基因组表达的线粒体定位蛋白，是TS，缺乏SIRT3的细胞表现出IR诱导的基因组不稳定性增加。因此，本研究的首要目标是确定SIRT3、线粒体代谢，特别是超氧化物水平、IR基因组不稳定性以及IR诱导的癌症之间的机制联系。在本研究中，我们假设SIRT3通过调节MnSOD活性和可逆乙酰赖氨酸的翻译后修饰来防止ir诱导的基因组不稳定性和致癌作用。此外，我们还提出赖氨酸乙酰化可能是用于调节线粒体蛋白的主要翻译后修饰。为了研究SIRT3、MnSOD和ir诱导的基因组不稳定性之间的机制联系，将使用一系列体外和体内模型系统。

DESCRIPTION (provided by applicant): Nuclear genome instability, a hallmark of cancer, is thought to be an early event in tumorigenesis including malignancies induced from IR either from incidental exposure or secondary to therapy. It is well established that mammalian cells contain fidelity proteins that appear to protect against both endogenous and exogenous forms of genotoxic stress including ionizing radiation (IR)-induced genomic instability. This idea is based on one of the fundamental paradigms in biology: that is mammalian cells contain fidelity proteins that recognize specific conditions, including cell damage, and subsequently initiate signaling cascades that maintain cellular homeostatic poise. In addition, loss of function or genetic mutation of these fidelity proteins has been shown to create tumor permissive cellular phenotype suggesting that these proteins also function as tumors suppressors (TS). Preliminary data in our laboratory suggests that SIRT3, which is a genomically expressed, mitochondrial localized protein, is TS and cells lacking SIRT3 exhibit increased IR- induced genomic instability. Thus, the overarching goal of this proposal is to determine a mechanistic connection between SIRT3, mitochondrial metabolism, specifically superoxide levels, and IR genomic instability as well as IR-induced cancers. In this proposal we hypothesize that SIRT3 protects against IR-induced genomic instability and carcinogenesis via the regulation of MnSOD activity and the post translation modification of a reversible acetyl lysine. In addition, we are also proposing that lysine acetylation may be a primary posttranslational modification employed to regulate mitochondrial proteins. To investigate a mechanistic connection between SIRT3, MnSOD, and IR-induced genomic instability a series of in vitro and in vivo model systems will be used.