细胞分裂起始与细胞核去组装的分子调控机理研究

Cell proliferation, or the cell division cycle, is fundamental to existence of life. It is a well-coordinated process regulated by a variety of factors through distinct passways. The mitotic entry is part of this process under a well-organized and yet to be recognized mechanism, although many aspects of it have been extensively studied and found that a number of the mitotic kinases take crucial roles. Furthermore, during the mitotic entry, the cell nucleus with duplicated genomes undergoes disassembly, the nuclear envelope breaks down, the nuclear pore complex and the nuclear lamina disassemble, the chromatin condenses into chromosomes and the mitotic spindle assembles, all of which are essential for the proper cell division, although the mechanisms of these processes largely remain to be elucidated. Over the past decade, we have focused our study on the cell cycle regulation, especially on the mitotic entry and exit under the regulation of mitotic kinases such as CDKs, Auroras and PLKs and the nuclear reconstruction, and have achieved many progresses. In this study, we will focus on the mechanisms of mitotic entry and the nuclear disassembly through using the established approaches such as cell-free and in vivo systems in the lab to investigate the important signal transduction pathways and regulatory networks. The final goal of this project will be to get insight into a deep understanding of the mechanisms underlying the mitotic entry and the nuclear disassembly and contribute to the understanding of the related diseases therapy.

细胞分裂增殖是生物界赖以存在的最基本生命活动。在细胞分裂之前，已完成基因组复制的细胞核需要去组装，核膜崩解，染色质凝聚，纺锤体装配，为细胞分裂奠定基础。有关细胞分裂起始机制和细胞核去组装的机制研究一直是国际生物学研究领域最前沿的课题，也是相关医学领域的研究基础。深入了解其分子机理，不仅对深入认识生命活动的实质有着极其重要的理论意义，同时对深入认识相关疾病的发生发展和相关药物的筛选等至关重要。我们以往在细胞增殖调控和肿瘤发生机理研究方面已做了不少开创性研究工作，在细胞分裂起始和细胞核去组装方面做了许多深入研究，获得了一些比较深入的认识，尤其在细胞分裂调控关键性蛋白激酶如CDKs、Aurora和PLK激酶等酶活性调控机制以及激酶信号传递通路研究方面取得了实质性研究进展。本项目拟在以往工作的基础上，应用自己建立的爪蟾卵非细胞体系和细胞体系等实验手段，深入研究细胞分裂起始和细胞核去组装的分子机理。

细胞分裂起始机制和细胞核去组装的机制研究一直是国际生物学研究领域最前沿的课题。本项目对核膜崩解、染色质凝聚、纺锤体装配等细胞分裂起始阶段所发生的一系列事件进行了深入研究。研究结果显示：1）Aurora A 和Aurora B作为调节细胞分裂起始的关键激酶，可以通过空间定位调控来分别实现各自功能的精细化调节，从而促进纺锤体装配合染色体凝集。而在纺锤体组装过程中，微管结合蛋白EML3通过调节非中心体依赖的微管组装参与了纺锤体装配，同时细胞核转运受体蛋白Importin α1受到CDK1激酶的磷酸化，也有利于维持纺锤体的形态；2）调控DNA复制起始的蛋白Cdc6与中心体激酶Plk4拮抗性地调节了中心体的复制，CDC6还会参与调控rDNA的转录的起始。中心体蛋白Dzip1在细胞周期激酶Plk1调控下介导BBSome蛋白复合体在中心体微卫星处定位。纤毛作为中心体的附属结构，GSK3beta-Dzip1-Rab8通路可以调控细胞纤毛生长和进入有丝分裂之间的拮抗过程。PLK1激酶可以磷酸化Hh通路下游蛋白Gli1，关闭Hh通路在G2期的活性。而在下一个G0期，PKA激酶磷酸化Inversin蛋白，促进Smo蛋白到纤毛中定位，进而激活下游信号通路。3）当细胞进入有丝分裂后期，环形片层结构参与了核膜和核孔复合体的组装，而CDK4会快速降解，进入G1 期又重新合成，并来回穿梭于细胞核与细胞质之间，并由此促进了cyclinD1 逐渐集中定位到细胞核。细胞核内的cyclinD1 逐渐累计会进一步激活CDK4。综上，本项目顺利完成了计划书中所设定的目标，加深了对细胞增殖代谢的调控重要信号通路的理解，建立起关于中心体成熟、染色体凝集、细胞核崩解与纤毛解聚等重要的细胞事件的信号通路和网络模型。