Investigation of a Meiotic Recombination Hotspot

9728557马龙 减数分裂是大多数真核生物生命周期的必要组成部分，它是产生单倍体配子所必需的。 它也具有进化的重要性，因为自然选择作用的大部分变异都是在减数分裂过程中产生的。 在减数分裂中有许多独特的步骤，其中之一是高水平的遗传重组。 正确的染色体配对和正确的第一次减数分裂染色体分离也需要双染。 本研究的重点是S.酿酒酵母（面包酵母），其中重组经常发生在减数分裂中。 与HIS 2处的减数分裂重组相关的是高水平的两个减数分裂特异性双链DNA断裂（DSB）。 减数分裂中这种断裂的分布和性质，无论是在特定的热点和沿着整个酵母染色体，是一致的，作为中间体在减数分裂重组的作用。 该项目有两个目标：1完成HIS 2所需顺式作用序列的分析，以及HIS 2上发生的断裂; 2确定和研究负责HIS 2热点的反式因子。 在研究的一部分中，关于HIS 2热点的问题包括：1多少DNA足以让一个热点在任何地方被识别？ 2转录干扰假说在HIS 2上正确吗？ 3 DSB位点是否有明确的位点特异性（而非序列特异性）？ 3天然断裂位点之间是否存在竞争，它是否发生在顺式和/或反式？ 4.在DSB区域内发生了多少次实际中断？ 5.热点处的DSB末端是否齐平，或者它们是否有5'重叠？ 来自其他热点的数据给出了两个不同的答案。6.所有断裂位点（甚至是编码区的断裂位点）是否都位于染色质的“开放”区域？ 本研究的第二部分旨在寻找影响HIS 2热点的因素，但通常不重组，即，其在HIS 2处产生（或拮抗）重组发生环境。 这些因子可能包括至少三种类型的基因产物：1区域的长距离染色质结构所需的因子，2 DSB位点的短距离染色质结构所需的因子，和3不参与染色质结构的HIS 2基因座特异性因子。 这三种类型中的任何一种都可能影响其他热点，我们将进行实验来问这个问题。

9728557 Malone Meiosis is a required part of the life cycle for most eucaryotes; it is necessary for the production of haploid gametes. It has evolutionary importance as well, since much of the variation upon which natural selection acts is created during meiosis. There are a number of unique steps in meiosis, one of which is high levels of genetic recombination. Recombination is also required for proper chromosome pairing and for a proper first meiotic chromosome segregation. This research focuses on a region (a "hotspot") around the HIS2 gene in S. cerevisiae (baker's yeast) where recombination occurs frequently in meiosis. Correlated with meiotic recombination at HIS2 are high levels of two meiosis-specific double strand DNA breaks (DSBs). The distribution and properties of such breaks in meiosis, both at specific hotspots and along whole yeast chromosomes, is consistent with their role as intermediates in meiotic recombination. This project has two aims: 1 To finish the analysis of the cis-acting sequences required, and the breaks that occur, at HIS2, and 2 To define and study the trans-factors responsible for the HIS2 hotspot. The questions asked about the HIS2 hotspot in part of the research include: 1 How much DNA is sufficient for a hotspot to be recognized wherever it is located? 2 Is the transcriptional interference hypothesis correct at HIS2? 3 Is there a clear site (not sequence) specificity for DSB sites? 3 Is there competition between natural break sites, and does it occur in cis and/or in trans? 4 How many actual breaks occur in the region of the DSB? 5 Are the ends of the DSBs at hotspots flush or do they have 5' overlaps? Data from other hotspots gives two different answers. 6 Are all break sites (even those in coding regions) located in "open" chromatin regions? The second part of this research is aimed at finding factors which affect the HIS2 hotspot, but not recombination generally i.e., which create (or antagonize) the recombinogenic environ ment at HIS2 . Such factors might include at least three types of gene products: 1 Factors required for the long range chromatin structure of the region, 2 Factors required for short range chromatin structure at the DSB sites, and 3 Factors specific to the HIS2 locus not involved in chromatin structure. Any of these three types might affect other hotspots as well, and experiments will be conducted to ask that question.