背景:丝裂原激活的蛋白激酶(MAPK)通过将环境的物理化学波动转化为多种适应性反应来维持细胞稳态。这些反应涉及转录重新连接和细胞周期转换的调节,在其他人中。然而,应激条件如何影响有丝分裂的进展在很大程度上是未知的。有丝分裂检查点是一种监视机制,可以在染色体捕获缺陷的情况下抑制有丝分裂的退出,从而防止非整倍体的产生。在这项研究中,我们研究了MAPKPmk1在应激时有丝分裂退出的调节中的作用。
结果:我们表明,裂殖酵母细胞缺乏Pmk1,细胞完整性途径(CIP)的MAP激酶效应,对微管损伤过敏,并且在维持中期停滞方面存在缺陷。Epistasis分析表明,Pmk1参与维持主轴装配检查点(SAC)信号,并且它的删除是由于缺少Mad2和Mad3等核心SAC组件。引人注目的是,在不受干扰的生长过程中,pmk1Δ细胞的后期促进复合物(APC/C)激活剂Cdc20Slp1的水平增加了两倍。我们证明了Pmk1通过规范的MAPK对接位点与Cdc20Slp1N端物理相互作用。最重要的是,Cdc20Slp1池通过需要MAPK活性的机制在经历有丝分裂的应激细胞中快速降解,Mad3和蛋白酶体,从而导致延迟的有丝分裂退出。
结论:我们的数据揭示了MAPK在防止有丝分裂退出和胞质分裂激活方面的新功能。MAPKPmk1对Cdc20Slp1周转的调节提供了一个关键机制,通过该机制可以相对于环境条件调整有丝分裂退出的时间。
BACKGROUND: Mitogen-activated protein kinases (MAPKs) preserve cell homeostasis by transducing physicochemical fluctuations of the environment into multiple adaptive responses. These responses involve transcriptional rewiring and the regulation of cell cycle transitions, among others. However, how stress conditions impinge mitotic progression is largely unknown. The mitotic checkpoint is a surveillance mechanism that inhibits mitotic exit in situations of defective chromosome capture, thus preventing the generation of aneuploidies. In this study, we investigate the role of MAPK Pmk1 in the regulation of mitotic exit upon stress.
RESULTS: We show that Schizosaccharomyces pombe cells lacking Pmk1, the MAP kinase effector of the cell integrity pathway (CIP), are hypersensitive to microtubule damage and defective in maintaining a metaphase arrest. Epistasis analysis suggests that Pmk1 is involved in maintaining spindle assembly checkpoint (SAC) signaling, and its deletion is additive to the lack of core SAC components such as Mad2 and Mad3. Strikingly, pmk1Δ cells show up to twofold increased levels of the anaphase-promoting complex (APC/C) activator Cdc20Slp1 during unperturbed growth. We demonstrate that Pmk1 physically interacts with Cdc20Slp1 N-terminus through a canonical MAPK docking site. Most important, the Cdc20Slp1 pool is rapidly degraded in stressed cells undergoing mitosis through a mechanism that requires MAPK activity, Mad3, and the proteasome, thus resulting in a delayed mitotic exit.
CONCLUSIONS: Our data reveal a novel function of MAPK in preventing mitotic exit and activation of cytokinesis in response to stress. The regulation of Cdc20Slp1 turnover by MAPK Pmk1 provides a key mechanism by which the timing of mitotic exit can be adjusted relative to environmental conditions.