靶标信息
The entry of eukaryotic cells into mitosis is regulated by cdc2/CDK1 kinase activation, a process controlled at several steps including cyclin B1 nuclear accumulation and binding, and phosphorylation of cdc2/CDK1 at Thr161. At the end of mitosis, cyclin B1 is targeted for degradation by the anaphase-promoting complex (APC), allowing for cell cycle progression. A critical regulatory step in activating cdc2 during progression into mitosis is dephosphorylation of cdc2/CDK1 at Thr14 and Tyr15 . Phosphorylation of Histone H3 at Ser10 is tightly correlated with chromosome condensation during both mitosis and meiosis. Overcoming the G1/S checkpoint to commence DNA replication requires cyclin E, traversing the G2/M checkpoint to initiate mitosis requires cyclin B, and cyclin A is required for both S-phase and M-phase . Cyclin A availability is apparently the rate-limiting step for entry into mitosis, and cyclin A is required for completion of prophase. Thymidine kinases play a critical role in generating the DNA synthetic precursor deoxythymidine triphosphate (dTTP). Cytoplasmic thymidine kinase 1 (TK1) expression and activity are regulated in a cell cycle-dependent manner, accumulating during G1-phase to peak levels in S-phase before being degraded prior to cell division . The initiation of S phase begins with the formation of the pre-replication complex (pre-RC) in late mitosis/early G1 phase. CDT1 and cdc6 bind to the origin of DNA replication, which allows binding of the MCM2-7 complex. In order to ensure that replication occurs only once per cell cycle, geminin inhibits and destabilizes CDT1 during the S, G2 and M phases. At the metaphase/anaphase transition, geminin is degraded by the anaphase-promoting complex (APC) allowing for the formation of new pre-RC .
