Lew D J, Reed S I
Department of Molecular Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
J Cell Biol. 1995 May;129(3):739-49. doi: 10.1083/jcb.129.3.739.
Checkpoint controls are regulatory pathways that inhibit cell cycle progression in cells that have not faithfully completed a prior step in the cell cycle. In the budding yeast Saccharomyces cerevisiae, DNA replication and spindle assembly are monitored by checkpoint controls that prevent nuclear division in cells that have failed to complete these processes. During the normal cell cycle, bud formation is temporally coincident with DNA replication and spindle assembly, and the nucleus divides along the mother-bud axis in mitosis. In this report, we show that inhibition of bud formation also causes a dramatic delay in nuclear division. This allows cells to recover from a transient disruption of cell polarity without becoming binucleate. The delay occurs after DNA replication and spindle assembly, and results from delayed activation of the master cell cycle regulatory kinase, Cdc28. Cdc28 activation is inhibited by phosphorylation of Cdc28 on tyrosine 19, and by delayed accumulation of the B-type cyclins Clb1 and Clb2. These results suggest the existence of a novel checkpoint that monitors cell morphogenesis in budding yeast.
关卡控制是一种调节途径，可抑制那些未忠实地完成细胞周期中前一步骤的细胞的细胞周期进程。在出芽酵母酿酒酵母中，DNA复制和纺锤体组装由关卡控制进行监测，这些控制可防止未完成这些过程的细胞进行核分裂。在正常细胞周期中，芽的形成在时间上与DNA复制和纺锤体组装同时发生，并且细胞核在有丝分裂时沿母细胞-芽轴分裂。在本报告中，我们表明抑制芽的形成也会导致核分裂显著延迟。这使细胞能够从细胞极性的短暂破坏中恢复过来而不会变成双核。这种延迟发生在DNA复制和纺锤体组装之后，是由主细胞周期调节激酶Cdc28的延迟激活导致的。Cdc28的激活受到酪氨酸19位点上Cdc28磷酸化以及B型细胞周期蛋白Clb1和Clb2延迟积累的抑制。这些结果表明存在一种监测出芽酵母细胞形态发生的新型关卡。
