Dissecting the mechanism of increased genomic instability in aging yeast

项目总结 年龄是最大的致癌物，然而癌症发病率急剧增加的机制是 人类的年龄尚不清楚。为了更好地了解这一现象，我们在酵母中开发了一个系统 酿酒酵母概括了癌症的特征之一-基因组不稳定-作为一种 细胞年龄的作用。具体地说，我们研究了衰老和基因组不稳定之间的关系 酵母复制老化过程中不同染色体杂合性丢失(LOH)的监测。我们 发现老化的酵母母细胞在其体内的杂合性缺失增加了近100倍 后代。 最近，我们对这一现象有了更好的理解，并提出了一个工作假说。 这将与年龄相关的LOH分解为一系列相互关联的事件。它以损失或损坏开始， 线粒体DNA。这会导致线粒体膜内电位降低，进而导致 铁-硫簇(ISC)生物合成和/或组装成蛋白质所需的铁-硫簇(ISC)缺陷 保持基因组的完整性。这些基因组完整蛋白的功能减弱会导致 LOH水平增加。这一假设作为一个工作模型来阐述我们的问题和 接近了。 我们现在建议使用强大的资源和工具集合来测试这个假设中的步骤 在酿酒酵母中有售。作为这种方法的一部分，我们开发了一种可诱导的遗传系统，母亲 扩增计划(MEP)，首次允许复制老化的S. 用于生化、细胞生物学和遗传分析的啤酒细胞。这将使我们能够获得更多 了解衰老中最早的事件，最终导致与年龄相关的LOH。因为每一个 在这个进展到年龄相关的LOH的过程中是保守的，我们相信我们在 拟议的计划最终将可翻译为识别人类的候选基因和过程 同样受到衰老的影响，并导致与年龄相关的肿瘤发生。

PROJECT SUMMARY Age is the greatest carcinogen, yet the mechanism by which the incidence of cancer dramatically increases as humans age is unclear. In an effort to better understand this phenomenon, we developed a system in the yeast Saccharomyces cerevisiae that recapitulates one of the hallmarks of cancer - genomic instability - as a function of cellular age. Specifically, we examined the relationship between aging and genomic instability by monitoring loss of heterozygosity (LOH) on different chromosomes during replicative aging in yeast. We discovered that aging yeast mother cells underwent a switch to a nearly 100-fold increase in LOH in their progeny. Recently, we gained a better understanding of this phenomenon and have developed a working hypothesis that breaks the age-associated LOH into a series of connected events. It begins with a loss of, or damage to, the mtDNA. This leads to a reduction in the inner mitochondrial membrane potential ( ¿), which in turn leads to a defect in iron-sulfur cluster (ISC) biosynthesis and/or assembly of the ISCs into proteins required for maintenance of genome integrity. The reduced function of these genome integrity proteins then leads to increased levels of LOH. This hypothesis serves as a working model to formulate our questions and approaches. We now propose to test the steps in this hypothesis using the powerful collection of resources and tools available in S. cerevisiae. As part of this approach, we developed an inducible genetic system, the Mother Enrichment Program (MEP), which permits for the first time the facile isolation of replicatively aged S. cerevisiae cells for biochemical, cell biological and genetic analysis. This will permit us to gain further understanding of the earliest events in aging that ultimately lead to age-associated LOH. Because each of the processes in this progression to age-associated LOH are conserved, we believe that what we learn in the proposed plan will ultimately be translatable to identifying candidate genes and processes in humans that are similarly affected by aging and lead to age-related oncogenesis.