Iouk Tatiana, Kerscher Oliver, Scott Robert J, Basrai Munira A, Wozniak Richard W
Department of Cell Biology, University of Alberta, Edmonton, Alberta, T6G 2H7 Canada.
J Cell Biol. 2002 Dec 9;159(5):807-19. doi: 10.1083/jcb.200205068.
Aphysical and functional link between the nuclear pore complex (NPC) and the spindle checkpoint machinery has been established in the yeast Saccharomyces cerevisiae. We show that two proteins required for the execution of the spindle checkpoint, Mad1p and Mad2p, reside predominantly at the NPC throughout the cell cycle. There they are associated with a subcomplex of nucleoporins containing Nup53p, Nup170p, and Nup157p. The association of the Mad1p-Mad2p complex with the NPC requires Mad1p and is mediated in part by Nup53p. On activation of the spindle checkpoint, we detect changes in the interactions between these proteins, including the release of Mad2p (but not Mad1p) from the NPC and the accumulation of Mad2p at kinetochores. Accompanying these events is the Nup53p-dependent hyperphosphorylation of Mad1p. On the basis of these results and genetic analysis of double mutants, we propose a model in which Mad1p bound to a Nup53p-containing complex sequesters Mad2p at the NPC until its release by activation of the spindle checkpoint. Furthermore, we show that the association of Mad1p with the NPC is not passive and that it plays a role in nuclear transport.
在酿酒酵母中已建立了核孔复合体（NPC）与纺锤体检查点机制之间的物理和功能联系。我们发现，纺锤体检查点执行所需的两种蛋白质Mad1p和Mad2p在整个细胞周期中主要位于NPC处。在那里，它们与包含Nup53p、Nup170p和Nup157p的核孔蛋白亚复合体相关联。Mad1p-Mad2p复合体与NPC的关联需要Mad1p，并且部分由Nup53p介导。在纺锤体检查点激活时，我们检测到这些蛋白质之间相互作用的变化，包括Mad2p（而非Mad1p）从NPC释放以及Mad2p在动粒处积累。伴随这些事件的是Mad1p的Nup53p依赖性过度磷酸化。基于这些结果以及双突变体的遗传分析，我们提出了一个模型，其中与含Nup53p复合体结合的Mad1p将Mad2p隔离在NPC处，直到纺锤体检查点激活将其释放。此外，我们表明Mad1p与NPC的关联并非被动的，并且它在核运输中发挥作用。
