Regulation of cell cycle transitions by cyclin-dependent kinase in trypanosomes

项目摘要 细胞周期调控研究中的一个中心问题是，如何控制细胞周期转换， 在正确的时间过渡到下一个细胞周期阶段？这种控制机制对于 保持基因组的完整性，因为过早地从细胞周期的一个阶段过渡到下一个阶段 会导致非整倍体，从而导致细胞死亡。四个主要的细胞周期转换点，G1/S转换， G2/M转换，中期/后期转换，有丝分裂/胞质分裂转换，在严格的 控制，但它们是如何在T.布鲁氏菌，一种原生动物寄生虫， 人类昏睡病的病原体，仍然知之甚少。细胞周期蛋白依赖性激酶（CDKs）是关键 真核生物细胞周期转换的调节因子，以及T.布氏杆菌利用CDK相关激酶CRK 1， CRK 2控制G1/S转换，CRK 2促进S期进展，CRK 3控制G2/M转换。 CRK 1在控制核事件、促进G1/S转变中的作用以及CRK 2在 调节S期进展的基因最近被我们发现。然而，分子机制 G2/M转换和中期/后期转换的基础仍然难以捉摸。此外，它通常 接受了T。布鲁氏菌缺乏几个细胞周期检查点，包括纺锤体组装检查点， 目前还不清楚T。布氏杆菌识别细胞周期中发生的基因组错误并防止错误 基因组复制和过早的基因组分离。我们最近发现了一种新的DNA损伤- 诱导的中期检查点提示T.布鲁塞，但 潜在的机制在很大程度上仍然未知。目前的建议旨在了解控制的 通过CRK 3介导的染色体乘客复合物的调节进行G2/M转换， CRK 3介导的着丝粒蛋白调控的中期/后期转换，以及 由KKIP 5及其相关蛋白介导的中期检查点。这些成果 这些研究不仅具有重要的生物学意义，而且可以为抗肿瘤提供新的靶点。 锥虫化疗

Project Summary A central question in the study of cell cycle regulation is, how the cell cycle transitions are controlled to allow the transition to the next cell cycle stage at a right time? Such control mechanisms are critical for maintaining genome integrity because premature transition from one stage to the next stage of the cell cycle can lead to aneuploidy and, hence, cell death. Four major cell cycle transition points, the G1/S transition, the G2/M transition, the metaphase/anaphase transition, and the mitosis/cytokinesis transition, are under stringent control, but how they are regulated at the molecular level in T. brucei, a protozoan parasite and the causative agent of human sleeping sickness, remains poorly understood. Cyclin-dependent kinases (CDKs) are key regulators of the cell cycle transitions in eukaryotes, and T. brucei employs the CDK-related kinase CRK1 to control the G1/S transition, CRK2 to promote S-phase progression, and CRK3 to govern the G2/M transition. The roles of CRK1 in controlling the nuclear events in promoting the G1/S transition and the role of CRK2 in regulating S-phase progression have been recently revealed by us. However, the molecular mechanisms underlying the G2/M transition and the metaphase/anaphase transition are still elusive. Further, it is generally accepted that T. brucei lacks several cell cycle checkpoints, including the spindle assembly checkpoint, and it is unclear how T. brucei recognizes the genomic errors occurred during the cell cycle and prevents erroneous genome duplication and premature genome segregation. Our recent discovery of a novel DNA damage- induced metaphase checkpoint suggests a kinetochore-based checkpoint machinery in T. brucei, but the underlying mechanism remains largely unknown. The current proposal aims to understand the control of the G2/M transition by CRK3-mediated regulation of the chromosomal passenger complex, the control of metaphase/anaphase transition by CRK3-mediated regulation of kinetochore proteins, and the mechanism of the metaphase checkpoint mediated by KKIP5 and its associated proteins. The outcomes from these investigations not only will have important biological significance, but also could provide novel targets for anti- trypanosomiasis chemotherapy.