Functional Analysis of Recombination Proteins in Eukaryotes

在减数分裂过程中，单倍体配子是由二倍体亲本细胞产生的。在大多数生物中，染色体的减少分离伴随着同源染色体之间的遗传重组。减数分裂前期1发生的重组为染色体的合理分布和基因组多样性的产生提供了条件。在减数分裂过程中，染色体通过重组蛋白形成的各种复合体进行突触和重组，并表现出一系列的形态变化。为了了解重组的机制，我们研究了参与重组和修复受损DNA的复合体中的每一种蛋白质的作用机制。以小鼠和百合减数分裂中的染色体为材料，我们研究了染色体形态变化与重组蛋白定位的关系。我们发现RAD51和LIM 15蛋白在特定的时间定位于特定的位置。RAD51和LIM 15蛋白具有搜索和配对同源DNA序列的一般特性。百合减数分裂染色体上的这两个蛋白都表明，这些蛋白参与了细线期同源染色体的寻找，并导致了合线期的染色体配对。在小鼠减数分裂染色体中，Rad 51蛋白成为粗线期染色体联会复合体核心的组成部分，参与了双线期的交叉形成Lim15蛋白仅存在于粗线期至双线期的粗线期核心的两端，而不参与交叉的形成，而是参与端粒区的重组和前期1对染色体的分离。因此，RAD51和Lim15在减数分裂重组的后期阶段发挥着不同的作用。

In meiosis, haploid gametes are produced from diploid parental cells.In most organisms, this reductional segregation of chromosomes accompanies with genetic recombination between homologous chromosomes.The recombination that occurs in meiotic prophase 1 provides for proper distribution of chromosomes and for generation of genomic diversity.During meiosis, chromosomes synapse and recombine using various complexes formed by recombination proteins and show a series of morphological changes.To understand the mechanisms of the recombination, we are studying the mechanisms of action of each protein that constitutes in the complexes involved in recombination and repair of damaged DNA in yeast.By using the mouse and lily chromosomes in meiosis, we studied the relationships between morphological changes of chromosomes and the localization of the recombination proteins.We found that the Rad51 and Lim 15 proteins, that have general properties of searching and pairing of homologous DNA sequences, localize at specific positions at specific time.Both proteins on meiotic chromosomes of lily showed that these proteins participate in searching for homologous chromosomes on the leptotene stage and lead to chromosome pairing in zygotene stage.In mouse meiotic chromosomes, the Rad 51 protein becomes a component of the synaptonemal complex core in pachytene chromosomes and is involved in chiasma formation in the diplotene.On the other hand, the Lim15 protein is present only at both ends of cores in the pachytene through diplotene chromosomes even in diakinesis.The Lim15 protein is not involved in chiasma formation and instead, is involved in recombination in the telomeric region and in segregation of paired chromosomes in prophase 1.thus, it is evident that Rad51 and Lim15 play different roles in the late stages of meiotic recombination.