Bembenek Joshua, Kang Jungseog, Kurischko Cornelia, Li Bing, Raab Jesse R, Belanger Kenneth D, Luca Francis C, Yu Hongtao
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
Cell Cycle. 2005 Jul;4(7):961-71. doi: 10.4161/cc.4.7.1798. Epub 2005 Jul 10.
The mitotic exit network (MEN) controls the exit from mitosis in budding yeast. The proline-directed phosphatase, Cdc14p, is a key component of MEN and promotes mitotic exit by activating the degradation of Clb2p and by reversing Cdk-mediated mitotic phosphorylation. Cdc14p is sequestered in the nucleolus during much of the cell cycle and is released in anaphase from the nucleolus to the nucleoplasm and cytoplasm to perform its functions. Release of Cdc14p from the nucleolus during anaphase is well understood. In contrast, less is known about the mechanism by which Cdc14p is released from the nucleus to the cytoplasm. Here we show that Cdc14p contains a leucine-rich nuclear export signal (NES) that interacts with Crm1p physically. Mutations in the NES of Cdc14p allow Clb2p degradation and mitotic exit, but cause abnormal morphology and cytokinesis defects at non-permissive temperatures. Cdc14p localizes to the bud neck, among other cytoplasmic structures, following its release from the nucleolus in late anaphase. This bud neck localization of Cdc14p is disrupted by mutations in its NES and by the leptomycin B-mediated inhibition of Crm1p. Our results suggest a requirement for Crm1p-dependent nuclear export of Cdc14p in coordinating mitotic exit and cytokinesis in budding yeast.
有丝分裂退出网络（MEN）控制着芽殖酵母中从有丝分裂的退出。脯氨酸定向磷酸酶Cdc14p是MEN的关键组分，它通过激活Clb2p的降解以及逆转Cdk介导的有丝分裂磷酸化来促进有丝分裂退出。在细胞周期的大部分时间里，Cdc14p被隔离在核仁中，并在后期从核仁释放到核质和细胞质中以履行其功能。Cdc14p在后期从核仁的释放已得到充分了解。相比之下，关于Cdc14p从细胞核释放到细胞质的机制了解较少。在这里，我们表明Cdc14p含有一个富含亮氨酸的核输出信号（NES），它与Crm1p发生物理相互作用。Cdc14p的NES突变允许Clb2p降解和有丝分裂退出，但在非允许温度下会导致异常形态和胞质分裂缺陷。在后期晚期从核仁释放后，Cdc14p定位于芽颈以及其他细胞质结构中。Cdc14p的这种芽颈定位被其NES突变以及雷帕霉素B介导的Crm1p抑制所破坏。我们的结果表明，在芽殖酵母中协调有丝分裂退出和胞质分裂时，需要Crm1p依赖的Cdc14p核输出。
