Chromosome structure, duplication and stability in yeast

项目总结/摘要 真核基因组复制需要每个染色体碱基对被有效复制， 准确地说，每个细胞分裂只有一次，这是一个巨大的需求，因为数百万到数十亿的 组成真核生物基因组的碱基对，以及形成 并维持有机体。DNA复制的严重缺陷与生命不相容。然而，在这方面， 在这一过程中的轻微扰动，同时仍然能够支持细胞分裂， 使用生物化学方法识别具有挑战性，可能会损害发育， 在多次细胞分裂过程中保持健康。调控的第一步，DNA的起始 发生在染色体位置称为起点的复制，在 真核细胞，因为它们的染色体需要多个空间和时间分布 准确和有效的复制的起源。原点数或分布的扰动可以 促进癌症、干细胞老化或发育障碍。而原始结合蛋白 以及确定起源的分子步骤是已知的， 染色体起源数目和分布不清楚。一个挑战是染色质 作为基因组功能的固有部分， organization.因此，来源结合蛋白必须在不同的细胞内充分发挥作用。 染色质环境，以实现平衡竞争的起源分布水平， 对细胞增殖和基因组稳定性的需求。福克斯博士的实验室解决了 了解天然染色质结构如何调节起源功能， 遗传学和基因组学，以揭示染色质介导的机制，影响结构 和功能的酿酒酵母（酵母）的起源。重点放在第一步 起源形成，起源许可反应，发生在细胞周期的G1期， 在S期之前，起源执行其实际功能， 新的DNA合成。积累的证据表明，许可证的步骤是 特别是与基因组稳定性和细胞命运决定有关，但缺乏 关于它如何在体内调节以实现染色体起源的分子机制 分布起源结合蛋白的进化保守性及其多重特征 染色质允许福克斯实验室利用酵母的实验优势来定义 染色质和起始结合蛋白协作形成的基本机制 并在基因组中分配起源。

Project Summary/Abstract Eukaryotic genome duplication requires that each chromosomal base pair is copied efficiently, accurately and only once per cell division, a monumental demand given the millions to billions of base pairs that comprise eukaryotic genomes and the countless cell divisions required to form and sustain organisms. Severe defects in DNA replication are incompatible with life. However, mild perturbations in this process, while still capable of supporting cell division, and which can be challenging to identify using biochemical approaches, can compromise development and health over the course of multiple cell divisions. Regulation of the first step, the initiation of DNA replication that occurs at chromosomal positions called origins, is particularly critical in eukaryotic cells because their chromosomes require multiple spatially and temporally distributed origins for accurate and efficient duplication. Perturbations in origin number or distribution can promote cancer, stem cell aging, or developmental disorders. While the origin-binding proteins and molecular steps that define an origin are known, the mechanisms that regulate chromosomal origin number and distribution are unclear. A challenge is that chromatin heterogeneity exists across chromosomes as an intrinsic part of genome functional organization. Thus, the origin-binding proteins must work sufficiently enough within distinct chromatin environments to achieve a level of origin distribution that balances the competing demands for cell proliferation and genome stability. Dr. Fox's lab addresses the gaps in understanding how native chromatin structures regulate origin function by combining rigorous genetics and genomics to reveal chromatin-mediated mechanisms that impinge on the structure and function of Saccharomyces cerevisiae (yeast) origins. Emphasis is placed on the first step of origin formation, the origin licensing reaction, which occurs in G1-phase of the cell cycle that precedes the S-phase where origins perform their actual function, unwinding of the parental DNA for new DNA synthesis. Accumulating evidence reveals that the licensing step is particularly relevant to both genome stability and cell-fate decisions, but there is a paucity of molecular mechanisms regarding how it is regulated in vivo to achieve chromosomal origin distribution. Evolutionary conservation of the origin-binding proteins and multiple features of chromatin allow the Fox laboratory to leverage the experimental strengths of yeast to define fundamental mechanisms by which chromatin and the origin-binding proteins collaborate to form and distribute origins over the genome.