Characterization of genes isolated in a novel screen for mutants with altered mitotic lifespan in yeast

导言：几个世纪以来，为什么所有的生物都在年龄上一直是一个最耐人寻味的问题。使用简单的模型系统，如苍蝇、蠕虫和酵母，已经识别出对细胞和整个动物寿命有很大影响的单一保守基因。单细胞和多细胞生物体的健康状况是衡量细胞维持寿命的能力。每个细胞都经历了一系列的分裂，直到达到分化或衰老状态。 最新进展：我们设计并实施了第一个全基因组范围的酵母突变株筛选，这些突变株在衰老之前经历了不同数量的细胞分裂。筛选出48个寿命延长的突变体和87个寿命缩短的突变体。许多已识别的突变体定义了以前没有与调节寿命相关的细胞过程，并涉及参与蛋白质运输和铁运输的基因。 目的：这项提案将重点检验我们的核心假设，即：i)蛋白质运输是酵母细胞寿命的一个不可或缺的决定因素，以及ii)铁摄取和细胞运输受损导致酵母过早衰老。 方法：采用复制寿命试验(RLS)对筛选到的突变株的寿命表型进行确认。最初的特征将包括对相互作用进行遗传分析，以确定功能途径。表征遗传相互作用和潜在的上位性被用于在分层路径中放置因素，这是我们在过去广泛依赖的一种方法。加拿大光源(CLS)的同步加速器将用于研究，旨在确定突变体中是否积累了游离铁，并表征了通常随年龄积累的铁物种。 影响：我们在酵母中发现的基因也在人类中发现，这表明我们在酵母中的发现将允许在高等真核系统的衰老研究中探索新的研究途径。

INTRODUCTION: Why all living organisms age has been a most intriguing question for centuries. Using simple model systems, such as flies, worms, and yeast, single conserved genes have been identified that greatly impact cellular and whole animal lifespan. The health of single cell and multicellular organisms is a measure of cellular capacity to maintain lifespan. Every cell undergoes a series of divisions until a differentiated or senescent state is reached. RECENT PROGRESS: We have designed and implemented the first genome-wide screen for yeast mutants that experience an altered number of cell divisions prior to senescence. The screen yielded 48 mutants with increased lifespan and 87 with reduced lifespan. Many of the identified mutants define cellular processes that have not been previously linked with regulating lifespan, and implicate genes involved in protein trafficking and iron transport. OBJECTIVES: This proposal will focus on testing our central hypotheses that i) protein trafficking is an integral determinant of cellular lifespan in yeast, and ii) that impaired iron uptake and cellular transport results in premature aging in yeast. METHODS: The lifespan phenotypes of mutants identified in the screen will be confirmed using the replicative lifespan assay (RLS). The initial characterization will involve a genetic analysis of interactions to work out functional pathways. Characterizing genetic interactions and potential epistasis is utilized for placement of factors within hierarchical pathways, an approach that we have extensively relied on in the past. The synchrotron at the Canadian Light Source (CLS) will be employed in studies aimed at determining whether free iron accumulates in the mutants and to characterize the iron species that normally accumulate with age. IMPACT: The genes we have identified in yeast are also found in humans, suggesting that our findings in yeast will allow new avenues of research to be explored in aging studies in higher eukaryotic systems.