The role of the proteins Kar9 and Myo2 in orienting the mitotic spindle of budding yeast
The role of the proteins Kar9 and Myo2 in orienting the mitotic spindle of budding yeast
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DOI：
10.1016/s0960-9822(00)00837-x
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发表时间：
2000-11-30
期刊：
影响因子：
9.2
通讯作者：
Bloom, K
中科院分区：
文献类型：
--
作者：
Beach, DL;Thibodeaux, J;Bloom, K
背景：两种遗传“途径”有助于酵母芽殖过程中核分离的保真度。早期的途径，包括Kar9p和其他蛋白质，使有丝分裂纺锤体沿着母芽轴定向。在后期开始时，细胞质动力蛋白为细胞核进入芽提供动力。任何一条通路的缺失都会导致核迁移缺陷；失去两者都是致命的。在这里，为了可视化导致正确纺锤体沿母芽轴方向的功能步骤，我们将表达Kar9p和dynein的活酵母细胞成像为绿色荧光蛋白融合体。结果：Kar9p在芽内的转运需要肌球蛋白Myo2p。Kar9p通过微管结合蛋白Bim1p与微管相互作用，促进微管渗透到芽中。一旦微管进入芽，Kar9p就为在芽皮层捕获微管提供了平台。在芽中微管缩短的部位也观察到Kar9p，表明Kar9p将微管缩短与核迁移结合在一起。结论：因此，Kar9p在细胞周期早期提供了肌动蛋白细胞骨架和微管之间的关键链接。Kar9p和Myo2p之间的合作机制促进了纺锤体的前期定位。随后，Kar9p将微管分解与核迁移结合在一起。
Background: Two genetic 'pathways' contribute to the fidelity of nuclear segregation during the process of budding in the yeast Saccharomyces cerevisiae. An early pathway, involving Kar9p and other proteins, orients the mitotic spindle along the mother-bud axis. Upon the onset of anaphase, cytoplasmic dynein provides the motive force for nuclear movement into the bud. Loss of either pathway results in nuclear-migration defects; loss of both is lethal. Here, to visualize the functional steps leading to correct spindle orientation along the mother-bud axis, we imaged live yeast cells expressing Kar9p and dynein as green fluorescent protein fusions.Results: Transport of Kar9p into the bud was found to require the myosin Myo2p. Kar9p interacted with microtubules through the microtubule-binding protein Bim1p and facilitated microtubule penetration into the bud. Once microtubules entered the bud, Kar9p provided a platform for microtubule capture at the bud cortex. Kar9p was also observed at sites of microtubule shortening in the bud, suggesting that Kar9p couples microtubule shortening to nuclear migration.Conclusions: Thus, Kar9p provides a key link between the actin cytoskeleton and microtubules early in the cell cycle. A cooperative mechanism between Kar9p and Myo2p facilitates the pre-anaphase orientation of the spindle. Later, Kar9p couples microtubule disassembly with nuclear migration.