Chromosome pairing and condensins

描述（由申请人提供）：我们工作的长期目标是了解不同染色体物理相互作用的分子机制。在本提案中，我们特别关注反式相互作用是如何被负调控的。在包括人类在内的许多物种的体细胞和减数分裂细胞中都存在染色体反式相互作用。目前对染色体反式相互作用的观点认为，蛋白质使染色体紧密接近，并允许基因表达或染色体分离的协调。例如，染色体反式相互作用对于小鼠嗅觉受体基因和小鼠TH 2 LCR基因座中的基因活化是重要的。在果蝇中也观察到各种反式相互作用，无论是在体细胞（例如transvection，trans-silencing，多线染色体）和减数分裂细胞中，广泛的相互作用配对同源染色体在其整个长度。减数分裂配对对于染色体的正确分离和表观遗传过程如X失活、印记和哺乳动物、植物和真菌中配对敏感的减数分裂基因沉默是重要的。体细胞和减数分裂配对都可以通过完全独立于DNA重组和修复蛋白的机制发生。在任何生物体中，染色体如何配对和解除配对在很大程度上都是未知的。虽然少数蛋白质已被描述为介导重组独立的减数分裂配对，有什么调控体细胞染色体配对一无所知。体细胞染色体和减数分裂染色体配对是否在结构上相似，或者它们是否受相同的因子调控，目前还不清楚。本实验室最近的工作表明，体细胞二倍体染色体配对、多线染色体配对和减数分裂染色体配对都受到凝聚素II复合体的拮抗。冷凝蛋白是如何做到这一点的尚不清楚。然而，我们的观察提供了第一个分子洞察体细胞配对机制，我们证明了一种新的染色体反配对功能的凝聚素。从细菌到人类，凝聚蛋白是保守的，因此了解它们如何调节染色体相互作用将揭示可能在所有物种中都很重要的基本功能。这一建议建立在我们最近对凝聚素的研究基础上。首先，我们将利用遗传学来鉴定与凝聚素合作调节多线染色体解配对的蛋白质。其次，我们将确定凝聚素调节二倍体体细胞中染色体配对敏感基因表达的机制。第三，我们将确定凝聚素的功能，以及它们的相互作用蛋白质，在调节减数分裂染色体配对。公共卫生相关性：我们试图了解不同染色体物理相互作用的分子机制。在这个建议中，我们特别关注反式相互作用是如何负调控的一组多蛋白质复合物称为凝聚素。染色体间的相互作用导致同源序列的配对对于减数分裂中的基因调控和染色体分离是重要的。我们提出的实验，将确定染色体反配对因子的凝聚素的分子功能。本资助申请中提出的实验将对生物医学研究和人类健康的进步产生直接和重大的影响。

DESCRIPTION (provided by applicant): The long term goal of our work is to understand the molecular mechanisms through which different chromosomes physically interact. In this proposal we focus specifically on how trans-interactions are negatively regulated. Chromosomal trans-interactions have been seen in somatic cells and meiotic cells of many species, including human. A current view of chromosome trans-interactions posits that proteins bring chromosomes into intimate proximity and allow coordination of gene expression or chromosome segregation. For example, chromosome trans-interactions are important for gene activation in the mouse olfactory receptor gene and the mouse TH2 LCR locus. A variety of trans-interactions also have been observed in Drosophila, both in somatic cells (e.g.transvection, trans-silencing, polytene chromosomes) and in meiotic cells where extensive interactions pair homologous chromosomes throughout their lengths. Meiotic pairing is important for proper chromosome segregation and for epigenetic processes such as X-inactivation, imprinting, and pairing-sensitive meiotic gene silencing in mammals, plants and fungi. Both somatic and meiotic pairing can occur by mechanisms that are completely independent of DNA recombination and repair proteins. How chromosomes pair and unpair is largely unknown in any organism. Although a handful of proteins have been described to mediate recombination independent meiotic pairing, there is nothing known about what regulates somatic chromosome pairing. It is not known whether somatic and meiotic chromosome pairing are structurally similar or if they are regulated by the same factors. Work from my laboratory has recently demonstrated that pairing of somatic diploid chromosomes, polytene chromosome pairing and meiotic chromosome pairing are all antagonized by the condensin II complex. How condensins do this is unclear. However, our observations provide the first molecular insight into a somatic pairing mechanism, and we demonstrate a novel chromosome anti-pairing function for condensins. Condensins are conserved from bacteria to humans, therefore understanding how they regulate chromosome interactions will reveal basic functions likely to be important in all species. This proposal builds on our recent work on condensin. First, we will use genetics to identify the proteins that cooperate with condensins to regulate polytene chromosome unpairing. Second, we will determine the mechanism(s) through which condensins regulate chromosome pairing sensitive gene expression in diploid somatic cells. Third, we will determine the function of condensins, and their interacting proteins, in regulating meiotic chromosome pairing. PUBLIC HEALTH RELEVANCE: We seek to understand the molecular mechanisms through which different chromosomes physically interact. In this proposal we focus specifically on how trans- interactions are negatively regulated by a set of multi-protein complexes known as condensins. Chromosome interactions leading to pairing of homologous sequences is important for gene regulation and chromosome segregation in meiosis. We propose experiments that will determine the molecular function of condensins as chromosome anti-pairing factors. The experiments proposed in this grant application will have a direct and significant impact on the advancement of biomedical research and human health.