From G1 regulators to Replication machinery

从 G1 调节器到复制机器

基本信息

批准号：
12141101
负责人：
MASAI Hisao
金额：
$ 64.51万
依托单位：
Tokyo Metropolitan Institute of Medical Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12141101/
关键词：
G1-S transition E2F transcription factor prereplicative complex MCM complex Cdc7 kinase Cyclin-dependent kinase Nuclear Matrix Attachment Clamp-Clamp loader G1-S期移行リン酸化細胞周期 DNA複製開始 Cdcキナーゼ DNAヘリカーゼ MCM ES細胞 Cdc7-ASKキナーゼ /

项目摘要

G1 signals activate Cdk4-CyclinD, which in turn activates E2F by phosphorylation of Rb. Our results show that E2F induces not only factors required for G1-S transition but also S phase regulators, checkpoint proteins, repair factors and G2-M transition factors. This will lead to activation of growth cycle and brings about coordinated progression of S phase as well as subsequent mitotic events. Replication factors induced by E2F promote generation of prereplicative complexes on the chromatin. This process may be intimately linked to interaction of replication machinery with nuclear matrix through transcription factors. Cdk and Cdc7 phosphorylates the N-terminal tails of MCM2 and MCM4 proteins and this phosphorylation results in recruitment of additional replication factors including Cdc45. MCM helicase is activated specifically by the single-stranded thimine-rich sequences which may be exposed during this step. Multiple clamp-clamp loader systems operate during the operation of replication forks, permitting the coordinated execution of fork-related activities including DNA synthesis, sister chromatid cohesion, and chromatin assembly. Tauti-potent stem cells undergo specific cell cycle program which may be achieved by overexpression of a subset of crucial replication/ cell cycle regulators. In cancer cells, the steady-state expression levels of the replication factors are distinctively different from the normal cells, and downregulation of replication factors in cancer cells often leads to induction of cell death, raising a possibility that replication factors could be novel targets for cancer therapy. On the other hand, deregulation of some critical factors including Cdt1 leads to induced genetic instability which may results in malignant growth.

G1 信号激活 Cdk4-CyclinD，后者又通过 Rb 磷酸化激活 E2F。我们的结果表明，E2F 不仅诱导 G1-S 转变所需的因子，还诱导 S 期调节因子、检查点蛋白、修复因子和 G2-M 转变因子。这将导致生长周期的激活并带来S期以及随后的有丝分裂事件的协调进展。 E2F 诱导的复制因子促进染色质上复制前复合物的生成。这一过程可能与复制机制通过转录因子与核基质的相互作用密切相关。 Cdk 和 Cdc7 磷酸化 MCM2 和 MCM4 蛋白的 N 末端尾部，这种磷酸化导致招募其他复制因子，包括 Cdc45。 MCM 解旋酶被在此步骤中可能暴露的富含硫胺素的单链序列特异性激活。多个夹钳加载系统在复制叉运行期间运行，允许协调执行与复制叉相关的活动，包括 DNA 合成、姐妹染色单体凝聚和染色质组装。强效干细胞经历特定的细胞周期程序，这可以通过关键复制/细胞周期调节因子的子集的过度表达来实现。在癌细胞中，复制因子的稳态表达水平与正常细胞明显不同，癌细胞中复制因子的下调通常会导致细胞死亡，这增加了复制因子可能成为癌症新靶点的可能性治疗。另一方面，包括 Cdt1 在内的一些关键因素的失调会导致诱导遗传不稳定，从而可能导致恶性生长。