Roles of chromosomal factors in chromosome segregation

描述（由申请人提供）：在细胞分裂过程中，染色体必须均匀分离。真核生物使用微管来控制染色体的定位和运动。除了着丝粒和中心体，构成染色体臂的染色质在组织纺锤体微管中起着重要作用。这项提案的长期目标是了解染色体因素如何影响当地环境并协调染色体分离。为了实现这一目标，我们使用表达筛选来鉴定新的中期染色体结合蛋白，并发现了Dasra A和Dasra B，这是脊椎动物染色体乘客复合物的两个新组分，其包含激酶Aurora B。该复合物在纺锤体检查点和胞质分裂中起作用，并且已经提出调节微管动力学。尽管Dasra B在脊椎动物中是保守的，但Dasra A同源物可以在鱼类、青蛙和鸡中找到，但在哺乳动物中没有。含有Dasra A的脊椎动物与哺乳动物的区别之一是早期胚胎细胞的快速分裂，在此期间检查点控制被抑制，这表明Dasra A可能专门用于调节这些快速细胞分裂周期中的纺锤体组装。使用爪蟾卵提取物，我们建议：1）确定染色体乘客复合体的全部成分。2)区分Dasra A和Dasra B在染色质诱导的纺锤体组装、纺锤体组装检查点的激活/维持以及Aurora B激酶活性调节中的功能。3)检查染色体乘客复合体如何在染色体上调节。染色体是否生化激活了染色体乘客复合体，或者染色体只是用来增加复合体的局部浓度？这一发现将帮助我们理解正常细胞如何准确地分离染色体，以及这一过程在癌细胞和出生缺陷中如何失败。

DESCRIPTION (provided by applicant): Chromosomes must be equally segregated during cell division. Eukaryotes use microtubules to control the positioning and movement of chromosomes. In addition to kinetochores and centrosomes, the chromatin that makes up the chromosome arms plays important roles in organizing spindle microtubules. The long-term goal of this proposal is to understand how chromosomal factors influence the local environment and coordinate chromosome segregation. To approach this goal, we used expression screening to identify new metaphase chromosome-binding proteins, and discovered Dasra A and Dasra B, two new components of the vertebrate chromosomal passenger complex, which contains the kinase Aurora B. This complex plays roles in the spindle checkpoint and cytokinesis, and it has been proposed to regulate microtubule dynamics. Whereas Dasra B is conserved among vertebrates, Dasra A homologs can be found in fishes, frogs and chicken, but not in mammals. One of the characteristics distinguishing Dasra A-containing vertebrates from mammals is the rapid early embryonic cell divisions during which the checkpoint controls are suppressed, suggesting that Dasra A may be specialized to regulate spindle assembly in these rapid cell division cycles. Using Xenopus egg extracts, we propose to: 1) Determine the full constituents of the chromosomal passenger complex. 2) Distinguish the functions of Dasra A and Dasra B in chromatin-induced spindle assembly, in activation/maintenance of the spindle assembly checkpoint, and in the regulation of the kinase activity of Aurora B. 3) Examine how the chromosomal passenger complex is regulated on chromosomes. Do chromosomes biochemically activate the chromosomal passenger complex, or are chromosomes simply used for increasing local concentration of the complex? The findings of this proposal will help us understand how normal cells segregate their chromosomes accurately and how this process fails in cancer cells and in birth defects.