Molecular Organization of Yeast Chromosome I - Control of Meiotic Pairing and Recombination

酵母 I 号染色体的分子组织 - 减数分裂配对和重组的控制

• 批准号: 0821900
• 负责人: David Kaback
• 金额: --
• 依托单位: Rutgers, The State University of New Jersey-RBHS-New Jersey Med
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-01 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0821900&HistoricalAwards=false
• 关键词: Molecular; Organization; Yeast; Chromosome; Control

Reciprocal recombination (crossing over) between homologous chromosomes (homologues) is believed to be required for proper meiosis I segregation. The mechanisms that control recombination so that each pair of homologues undergoes crossing over are not known. In Saccharomyces cerevisiae and humans, small chromosomes have higher meiotic reciprocal recombination rates (cM/kb) than large chromosomes, and in S. cerevisiae, rates of reciprocal recombination have been shown to respond directly to chromosome size. One set of recent experiments, however, suggested that size-dependent control of crossing over was not a general feature in all strains or on all chromosomes. As it has been proposed that size-dependent control of recombination is an essential feature of the mechanism guaranteeing crossing over between homologues, the investigator plans to find out if it indeed occurs in all strains and chromosomes and, if it does not, to begin to determine why it might not be occurring. The decreased rates of recombination on large chromosomes have been proposed to be due to increased crossover interference. Interference is defined by the apparent inhibition of additional meiotic reciprocal recombination events observed near the site of a crossover. The molecular mechanism of interference and how it might respond to chromosome size are not known. It has been suggested that the density of meiotic recombination-inducing double-strand break (DSB) sites is greater on small chromosomes than on large ones. If this is indeed the case, then chromosome size-dependent control of recombination (and, perhaps, interference) might act by controlling DSB formation. To test this idea, the investigator plans to analyze DSB formation on chromosome I constructs of different sizes. The investigator has also discovered that the most distal euchromatic DNA undergoes meiotic recombination at a higher rate than more interior sequences, suggesting that chromosome position also regulates recombination. The investigator will determine whether chromosome position does actually affect recombination rates. The next part of this project involves the meiotic synaptonemal complex (SC). The precise function of this structure is not known, but it has been proposed that it may serve as a regulator of meiotic recombination. The investigator has produced a functional, fluorescent ZIP1-GFP fusion protein that labels SCs in living cells. He has used this protein to show that SCs undergo dynamic movements and changes in their distribution. The role of these movements is unknown but they could play a role in facilitating recombination. He now proposes to label axial elements with REC8-CFP and, through the use of fluorescence video microscopy, examine the dynamics of pairing and SC movements. These studies should provide new insights into the molecular mechanisms controlling recombination and chromosome synapsis, processes that lead to proper meiotic chromosome segregation.In most species, proper chromosome segregation is essential for the production of normal gametes (e.g. sperm, eggs, pollen, and ascospores). Identifying mechanisms that ensure proper chromosome segregation will provide a better understanding of how meiotic divisions occur. A better understanding of these mechanisms could lead to greatly improved plant breeding and animal husbandry. Having this research carried out at UMDNJ in Newark will also be important for the scientific education of both graduate and medical students at that institution, and for the undergraduates from neighboring institutions (NJIT, Rutgers) who will actively participate in the project. Furthermore, UMDNJ's location has been instrumental in the investigator's significant success in enabling gifted underrepresented minority students to participate in research. He will continue this effort with the aim of producing outstanding scientists from UMDNJ's environs. The opening of Newark's Science High School one block from his laboratory should further increase his and his laboratory's impact upon Newark's secondary school population as well.

据信同源染色体（同源物）之间的相互重组（交叉）被认为是适当的减数分裂I分离所必需的。控制重组的机制以使每对同源物都经过交叉，尚不清楚。在酿酒酵母和人类中，小染色体比大染色体具有更高的减数分裂相互重组率（CM/kb），而在酿酒酵母中，互惠重组的发生率已被证明可以直接响应染色体对大小。然而，一组最新的实验表明，在所有菌株或所有染色体上，对交叉的大小依赖性控制并不是一般特征。由于已经提出，重组的大小依赖性控制是确保同源物之间跨越的机制的重要特征，因此研究者计划找出它是否确实发生在所有菌株和染色体中，如果没有，则开始确定为什么不会发生这种情况。 大型染色体上的重组率降低是由于交叉干扰增加所致。干扰是通过明显抑制了在交叉部位附近观察到的其他减数分裂相互重组事件的明显抑制。尚不清楚干扰分子机制及其对染色体大小的反应。有人提出，小染色体上的减数分裂重组诱导双链破裂（DSB）位点的密度大于大染色体。 如果确实如此，那么染色体大小依赖性控制重组（也许是干扰）可能会通过控制DSB的形成来起作用。为了测试这一想法，研究者计划分析DSB的染色体I构造的DSB形成。 研究者还发现，最远端的正式DNA以比更多内部序列更高的速率进行减数分裂重组，这表明染色体位置也调节重组。 研究者将确定染色体位置是否确实影响重组率。该项目的下一部分涉及减数分裂的突触综合体（SC）。 该结构的确切功能尚不清楚，但已提出它可以作为减数分裂重组的调节剂。研究者生产了一种功能性的荧光Zip1-GFP融合蛋白，该蛋白在活细胞中标记SC。他使用这种蛋白质表明SC经历了动态运动及其分布的变化。这些运动的作用尚不清楚，但它们可以在促进重组中发挥作用。他现在建议将轴向元素用REC8-CFP标记，并通过使用荧光视频显微镜检查配对和SC运动的动力学。这些研究应提供有关控制重组和染色体突触的分子机制的新见解，这些过程会导致适当的减数分裂染色体隔离。在大多数物种中，适当的染色体分离对于产生正常配子是必不可少的（例如精子，鸡蛋，花粉和腹部）。 确定确保正确的染色体分离的机制将更好地了解减数分裂分裂的发生方式。 更好地了解这些机制可能会大大改善植物育种和畜牧业。 在纽瓦克的Umdnj进行的这项研究对于该机构的研究生和医学生的科学教育以及将积极参与该项目的邻近机构（NJIT，RUTGERS）的本科生也很重要。此外，Umdnj的位置在调查人员的巨大成功方面发挥了作用，使有天赋的人数不足的少数族裔学生能够参加研究。他将继续这项努力，目的是从Umdnj的周围生产杰出的科学家。纽瓦克科学高中（Newark's Science High School）离实验室一个街区的开放应进一步增加他和他的实验室对纽瓦克（Newark）中学人口的影响。