Checkpoints and Double Strand Breaks in S. Pombe Meiosis

描述（由申请人提供）：忠实的染色体分离对于产生有活力的减数分裂产物至关重要。虽然对未受干扰的减数分裂染色体分离的调节已经被很好地理解，但当细胞在意想不到的DNA损伤的情况下试图减数分裂时会发生什么却鲜为人知。本研究利用分裂酵母模型系统研究减数分裂过程中DNA损伤的反应。裂变酵母是分析细胞周期损伤反应的一个强大系统，与人类共享许多调控基因。先前的研究表明，在增殖细胞中起作用的检查点系统在DNA损伤时阻断细胞周期，但在减数分裂中不起作用。导致复制分叉崩溃的条件似乎与减数分裂过程是相容的。减数分裂过程和增殖细胞对烷基化损伤的反应之间存在遗传联系，这表明翻译合成聚合酶可能在减数分裂中起作用。这些观察结果表明，减数分裂对DNA损伤的反应在分化过程中基本上是重新编程的。这是当前项目的更新，该项目已获得ARRA（刺激）资金资助1年。第一个目的是解决损伤检查点激酶Chk1如何在减数分裂中被重编程，使其在S期对损伤不作出反应的问题。第二个目标是研究减数分裂细胞如何适应在增殖过程中可能致命的复制分叉。第三个目标提出了跨损伤合成（TLS）聚合酶在减数分裂中的新作用。这是基于两个观察结果：第一，在S期起作用的DDK激酶也调节减数分裂和TLS，第二，激酶中功能等位基因的分离特异性地破坏减数分裂和TLS。长期目标是了解在meiS阶段损伤反应的调节如何被修改以使后期减数分裂事件发生。目的是利用裂变酵母来剖析减数分裂细胞对复制应激和s期损伤的不同反应的分子机制。其基本原理是，了解促进减数分裂中基因组稳定性的机制，将有助于确定影响人类流产和出生缺陷的遗传和环境风险因素。核心假设是，通常保护基因组的保守活动在减数分裂中被选中，以允许程序性遗传损伤。该项目的预期成果是鉴定和表征新的分子途径。这些将包括潜在的新因素，可能在高等真核生物中保守。积极的影响将是理解分化细胞对DNA损伤和基因组稳定性的反应的根本进步，并更好地了解减数分裂过程中的危险因素。

DESCRIPTION (provided by applicant): Faithful chromosome segregation is essential to the production of viable meiotic products. While the regulation of unperturbed meiotic chromosome segregation is well understood, it is less known what happens when cells attempt meiosis in the presence of unexpected DNA damage. This proposal investigates the response to DNA damage in meiosis, using a fission yeast model system. Fission yeast is a powerful system in the analysis of damage response in the cell cycle, sharing many regulatory genes with humans. Previous studies have shown that the checkpoint system that works in proliferating cells to block the cell cycle in response to DNA damage is not functional in meiosis. Conditions that cause replication fork collapse appear to be compatible with meiotic progression. There is a genetic link between meiotic progression and the response of proliferating cells to alkylation damage that suggest translation synthesis polymerases may play a role in meiosis. These observations suggest that the meiotic response to DNA damage is substantially reprogrammed during differentiation. This is a renewal of a current project that has been funded for 1 year from ARRA (stimulus) funding. The first aim addresses the question of how the damage checkpoint kinase, Chk1, is reprogrammed in meiosis so that it does not respond to damage during S phase. The second aim asks how meiotic cells accommodate collapsing replication forks, which would be lethal during proliferation. The third aim proposes a novel role for trans-lesion synthesis (TLS) polymerases in meiosis. This is based on two observations: first, that the DDK kinase which functions during S phase also regulation meiosis and TLS, and second, that a separation of function allele in the kinase specifically disrupts meiotic divisions and TLS. The long term goal is to understand how the regulation of the damage response during meiS phase is modified to enable later meiotic events. The objective is to use fission yeast to dissect the molecular mechanisms that differ in the response to replication stress and S-phase damage in meiotic cells. The rationale is that knowledge of mechanisms that promote genome stability in meiosis will allow identification of genetic and environmental risk factors that impact human miscarriages and birth defects. The central hypothesis is that conserved activities that normally function to protect the genome are co-opted in meiosis to allow programmed genetic damage. The expected outcomes of this project are the identification and characterization of new molecular pathways. These will include potentially novel factors, likely to be conserved in higher eukaryotes. The positive impact will be a fundamental advance in understanding of the response of differentiating cells to DNA damage and genome stability, and a better understanding of risk factors during meiosis.