Metaphase to Anaphase Transition in Mitosis and Meiosis

描述(申请人提供)：在真核细胞分裂的正常过程中，染色体在S期复制，在前期紧凑和重组，在中期对齐。当细胞随后从中期过渡到后期时，复制的染色体被分离并分离到两个子细胞中的每一个。为了避免在染色体分离中出现致命的错误，细胞仔细地调节这种中期到后期的转变，否则这种转变将被后期促进复合体(APC/C)不可逆转地向前推进，APC/C是一种多聚体E3泛素连接酶。APC/C通过标记特定的蛋白质进行蛋白水解性破坏来驱动这种转变和随后的有丝分裂退出过程；它通过促进染色体结合蛋白的破坏来促进后期；它通过直接靶向细胞周期蛋白B和有丝分裂退出网络的元件来促进有丝分裂退出。在该项目的第一阶段，在产生减数分裂1-细胞停滞胚胎的突变线虫母亲的筛选中，分离了几个不同APC/C基因的多个温度敏感(Ts)等位基因。对这些等位基因的分析表明：a)APC/C是同源和姐妹染色单体分离所必需的，b)相同的细胞周期块在不同的细胞类型中可能具有不同的发育结果，以及c)亚型突变体可用于检测APC/C的中期后功能。为了扩大这些研究的范围，以包括APC/C调节因子、APC/C底物和其他与后期相关的减数分裂和/或细胞类型特定因素，本建议的具体目的是：1)探索emb-1的分子和功能特征，emb-1是不编码APC/C亚单位的单个中期I受阻突变体，以及2)开始研究在减数分裂染色体分离和/或分离中存在缺陷的新的ts突变体，这些突变体仍然发育成多细胞胚胎。这些研究将a)确定中期到后期转换中新的和保守的角色，b)估计有多少基因在这一关键转换中发挥作用，以及c)产生一个独特的ts等位基因集合，可以并将用于不同类型的减数分裂和有丝分裂细胞分裂的比较研究。

DESCRIPTION (provided by applicant): During the normal process of eukaryotic cell division, chromosomes are replicated during S-phase, compacted and restructured during prophase, and aligned during metaphase. As cells subsequently transition from metaphase-to-anaphase, the replicated chromosomes are separated and segregated to each of two daughter cells. To avoid lethal errors in chromosome segregation, cells carefully regulate this metaphase to anaphase transition which would otherwise be driven irreversibly forward by the anaphase-promoting complex (APC/C), a multimeric E3 ubiquitin ligase. The APC/C drives both this transition and the subsequent process of mitotic exit by tagging specific proteins for proteolytic destruction; it promotes anaphase by facilitating the destruction of chromosomal cohesion proteins, and it promotes exit by directly targeting cyclin B and elements of the mitotic exit network. In the first phase of this project, multiple temperature-sensitive (ts) alleles of several different APC/C genes were isolated in screens for mutant C. elegans mothers that produce meiotic 1-cell arrested embryos. Analysis of these alleles revealed that: a) the APC/C is required for homolog as well as sister chromatid separation, b) identical cell cycle blocks can have distinct developmental consequence in different cell types, and c) hypomorphic mutants can be used to examine the post-metaphase functions of the APC/C. With the goal of extending these studies to include APC/C regulators, APC/C substrates, and other anaphase-related meiotic and/or cell type specific factors, the specific aims of this proposal are: 1) to pursue the molecular and functional characterization of emb-1, the single metaphase I arrested mutant that does not encode an APC/C subunit, and 2) to initiate studies of new ts mutants with defects in meiotic chromosome separation and/or segregation which nevertheless develop into multi-cellular embryos. These studies will a) identify novel and conserved players in the metaphase-to-anaphase transition, b) provide an estimate of how many genes function during this critical transition, and c) generate a unique collection of ts alleles that can and will be used in comparative studies of different types of meiotic and mitotic cell divisions.