Eukaryotic Chromosome Replication

描述（由申请人提供）： DNA复制对生命至关重要，因此，细胞已经进化出监测复制保真度和协调复制完成与其他细胞周期事件的机制。 该项目的目标是了解细胞如何编排其染色体的复制，以及DNA复制中的缺陷如何导致最近发现的人类疾病。真核生物中的染色体复制是一个涉及每条染色体多个起始位点（起点）调节的过程。 起源在时间上表现出变化--不是所有的起源都在S期同时放电--在效率上也是如此--不是所有的起源都必然在每个细胞周期中放电。 此外，细胞似乎保持一个备份集的起源（休眠起源）在特殊情况下使用，这些起源可能在其基本控制属性不同。 因此，了解如何调控原产地使用对于了解如何保持基因组完整性至关重要。最近描述的三种与复制缺陷有关的遗传性疾病强调了这一概念：1）Meier-Gorlin综合征，其在对原产地许可至关重要的基因中存在点突变; 2）在编码与小鼠乳腺癌和人类生长异常相关的复制解旋酶的一部分的基因中存在点突变;和3）具有可由复制叉错误解释的倒置中心拷贝的人类节段性三重复制。酵母是研究DNA复制的理想模式生物，因为它的小染色体，明确的起始序列，易于改变染色体结构，以及遗传和基因组分析的特殊系统。 该项目将应用分子，遗传和基因组学方法的组合：发现酵母中起源效率和时间的调节剂，探索/研究有序复制如何有助于基因组稳定性。利用与人类疾病有关的基因的酵母直向同源物中的点突变来了解复制缺陷的下游后果，因为它们与人类健康和疾病有关，并识别缺陷的遗传和化学抑制因子，确定DNA复制错误是否是导致特定一类反向扩增子的原因，这些反向扩增子可能导致癌症进展和先天性拷贝数变异。这个项目将解决有关染色体复制控制生物学的突出问题：为什么起点在不同的时间启动复制，是什么区分不同时间类别的起点，什么是低效起点的分子基础，以及复制叉进展中的哪些缺陷使染色体位点倾向于反向扩增？此外，这项工作将使人们深入了解染色体复制错误导致的人类疾病，并可能导致诊断或治疗的进步。

DESCRIPTION (provided by applicant): PROJECT SUMMARY DNA replication is undeniably important for life and as a consequence, cells have evolved mechanisms to monitor replication fidelity and to coordinate completion of replication with other cell cycle events. The goal of this project is to understand how cells choreograph the duplication of their chromosomes, and how defects in DNA replication may contribute to some recently discovered disorders in humans. Chromosome replication in eukaryotes is a process that involves the regulation of multiple initiation sites (origins) per chromosome. Origins show variation in timing-not all origins fire at the same time in S phase-and in efficiency-not all origins necessarily firing in every cell cycle. In addition, cells appea to maintain a backup set of origins (dormant origins) for use under special circumstances and these origins may differ in their basic control properties. Understanding how origin use is regulated is therefore critical for understanding how genome integrity is maintained. This notion is underscored by three recently described genetic disorders with links to replication defects: 1) Meier-Gorlin Syndrome with its point mutations in genes essential for origin licensing; 2) a point mutation in a gene encoding part of the replicative helicase that is associated with breast cancer in mice and growth abnormalities in humans; and 3) human segmental triplications with an inverted central copy that can be explained by a replication fork error. Yeast is an ideal model organism for studying DNA replication because of its small chromosomes, well defined origin sequences, ease of altering chromosome structure, and exceptional systems for genetic and genomic analysis. This project will apply a combination of molecular, genetic and genomics approaches to: ¿ uncover modulators of origin efficiency and timing in yeast, to explore/investigate how orderly replication contributes to genome stability ¿ use point mutations in the yeast orthologs of genes involved in human disorders to understand the downstream consequences of defects in replication as they relate to human health and disease, and to identify genetic and chemical suppressors of the defects ¿ determine whether DNA replication errors are responsible for a particular class of inverted amplicons that can contribute to cancer progression and congenital copy number variants. This project will address outstanding questions regarding the biology of chromosome replication control: why do origins initiate replication at different times, what distinguishes origins in different temporal categories, what i the molecular basis for inefficient origins, and what defects in replication fork progression predispose chromosomal loci to inverted amplification? In addition, this work will give insight int human disorders resulting from errors in chromosome replication and could lead to diagnostic or therapeutic advances.