Function of Nucleophosmin/B23 in Centrosome Duplication

描述（由申请人提供）：染色体不稳定性是一种可怕的 在多步骤致癌过程中， 获得恶性表型所需的遗传病变。期间 在过去的几年里，有一个不正常的证据积累， 由于中心体复制失调而导致的中心体扩增 在人类肿瘤中很常见。中心体的有害后果 在有丝分裂期间，通过形成异常的 纺锤体由多个纺锤极组织，导致频率增加 染色体分离错误。因此，中心体过度扩增是一种 导致人类癌症中染色体不稳定的主要因素。 中心体复制由细胞周期蛋白依赖性激酶（CDK）2/细胞周期蛋白E触发 (and/或细胞周期蛋白A）。因为CDK 2/细胞周期蛋白E 也驱动细胞启动DNA合成， CDK 2/cyclin E在G1中晚期被认为是协调中心体 复制和其他细胞周期事件，包括DNA复制。我们有 最近发现，核磷蛋白（NPM）/B23是CDK 2的关键中心体靶点 在中心体复制的起始阶段。NPM/B23直接磷酸化 通过CDK 2/细胞周期蛋白E，并在CDK 2/细胞周期蛋白E E-介导的磷酸化。显微注射抗NPM/B23抗体以及 显性负性NPM/B23的表达抑制中心体复制。 这些结果表明，诱导的中心体NPM/B23的解离 CDK 2介导的磷酸化是启动细胞凋亡的关键事件。 中心体复制，构成中心体的许可系统 复制，确保中心体和DNA复制的协调， 以及限制中心体复制在单个细胞内发生一次 周期阐明NPM/B23在中心体复制中的功能作用， 特别是与CDK 2/细胞周期蛋白E（和细胞周期蛋白A）相关， 水平将提供重要的信息，以进一步了解 中心体复制的调节，这导致了设计 针对中心体复制的有效癌症干预方案。等 一种方法可能被证明是有效的，因为中心体复制，如DNA 复制，仅限于增殖细胞。此外，阻止 中心体复制过程导致染色体不稳定性的抑制 以及细胞分裂。

DESCRIPTION (provided by applicant): Chromosome instability is a formidable force in the multi-step carcinogenesis by facilitating the accumulation of genetic lesions required for the acquisition of malignant phenotypes. During last several years, there is an accumulation of evidence that abnormal amplification of centrosomes due to the deregulated duplication of centrosomes is common in human tumors. A deleterious consequence of centrosome hyperamplification is featured during mitosis by the formation of aberrant spindles organized by multiple spindle poles, leading to an increased frequency of chromosome segregation errors. Thus, centrosome hyperamplification is one major factor that contributes to chromosome instability in human cancers. Centrosome duplication is triggered by cyclin-dependent kinase (CDK)2/cyclin E (and/or cyclin A) in a kinase activity-dependent manner. Because CDK2/cyclin E also drives cells to initiate DNA synthesis, the temporal activation of CDK2/cyclin E occurring in the mid-late G1 is believed to coordinate centrosome duplication and other cell cycle events, including DNA replication. We have recently found that nucleophosmin (NPM)/B23 is a key centrosomal target of CDK2 in the initiation of centrosome duplication. NPM/B23 is directly phosphorylated by CDK2/cyclin E, and dissociates from the centrosomes upon CDK2/cyclin E-mediated phosphorylation. Microinjection of anti-NPM/B23 antibody as well as expression of a dominant negative NPM/B23 inhibits centrosome duplication. These results suggest that dissociation of centrosomal NPM/B23 induced by CDK2-mediated phosphorylation is a critical event for the initiation of centrosome duplication, constituting a licensing system for centrosome duplication, ensuring the coordination of centrosome and DNA duplication as well as restricting centrosome duplication to occur once within a single cell cycle. Elucidation of the functional role of NPM/B23 in centrosome duplication, especially in association with CDK2/cyclin E (and cyclin A), at a molecular level will provide crucial information for further understanding of the regulation of centrosome duplication, which leads to the potential of designing effective cancer intervention protocols targeting centrosome duplication. Such an approach may prove effective, since centrosome duplication, like DNA replication, is restricted to proliferating cells. Moreover, blocking the centrosome duplication process results in suppression of chromosome instability as well as cell division.