Kellogg D R, Murray A W
Department of Physiology, University of California, San Francisco 94143-0444, USA.
J Cell Biol. 1995 Aug;130(3):675-85. doi: 10.1083/jcb.130.3.675.
NAP1 is a 60-kD protein that interacts specifically with mitotic cyclins in budding yeast and frogs. We have examined the ability of the yeast mitotic cyclin Clb2 to function in cells that lack NAP1. Our results demonstrate that Clb2 is unable to carry out its full range of functions without NAP1, even though Clb2/p34CDC28-associated kinase activity rises to normal levels. In the absence of NAP1, Clb2 is unable to efficiently induce mitotic events, and cells undergo a prolonged delay at the short spindle stage with normal levels of Clb2/p34CDC28 kinase activity. NAP1 is also required for the ability of Clb2 to induce the switch from polar to isotropic bud growth. As a result, polar bud growth continues during mitosis, giving rise to highly elongated cells. Our experiments also suggest that NAP1 is required for the ability of the Clb2/p34CDC28 kinase complex to amplify its own production, and that NAP1 plays a role in regulation of microtubule dynamics during mitosis. Together, these results demonstrate that NAP1 is required for the normal function of the activated Clb2/p34CDC28 kinase complex, and provide a step towards understanding how cyclin-dependent kinase complexes induce specific events during the cell cycle.
NAP1是一种60-kD的蛋白质，它在芽殖酵母和青蛙中与有丝分裂周期蛋白特异性相互作用。我们研究了酵母有丝分裂周期蛋白Clb2在缺乏NAP1的细胞中的功能。我们的结果表明，即使Clb2/p34CDC28相关激酶活性升至正常水平，没有NAP1时Clb2也无法发挥其全部功能。在没有NAP1的情况下，Clb2无法有效诱导有丝分裂事件，细胞在短纺锤体阶段会经历长时间的延迟，此时Clb2/p34CDC28激酶活性处于正常水平。Clb2诱导从极性芽生长向各向同性芽生长转变的能力也需要NAP1。结果，在有丝分裂期间极性芽生长持续，导致细胞高度伸长。我们的实验还表明，Clb2/p34CDC28激酶复合物自身扩增能力需要NAP1，并且NAP1在有丝分裂期间微管动力学调节中起作用。总之，这些结果表明活化的Clb2/p34CDC28激酶复合物的正常功能需要NAP1，并为理解细胞周期蛋白依赖性激酶复合物如何在细胞周期中诱导特定事件迈出了一步。
