Lai L A, Morabito L, Holloway S L
Department of Biochemistry and Molecular Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA.
Mol Genet Genomics. 2003 Nov;270(2):156-64. doi: 10.1007/s00438-003-0912-5. Epub 2003 Aug 19.
The accurate segregation of sister chromatids at the metaphase to anaphase transition in Saccharomyces cerevisiae is regulated by the activity of the anaphase-promoting complex or cyclosome (APC/C). In the event of spindle damage or monopolar spindle attachment, the spindle checkpoint is activated and inhibits APC/C activity towards the anaphase inhibitor Pds1p, resulting in a cell cycle arrest at metaphase. We have identified a novel allele of a gene for an APC/C subunit, cdc16-183, in S. cerevisiae. cdc16-183 mutants arrest at metaphase at 37 degrees C, and are supersensitive to the spindle-damaging agent nocodazole, which activates the spindle checkpoint, at lower temperatures. This supersensitivity to nocodazole cannot be explained by impairment of the spindle checkpoint pathway, as cells respond normally to spindle damage with a stable metaphase arrest and high levels of Pds1p. Despite showing metaphase arrest at G2/M at 37 degrees C, cdc16-183 mutants are able to perform tested G1 functions normally at this temperature. This is the first demonstration that a mutation in a core APC/C subunit can result in a MAD2-dependent arrest at the restrictive temperature. Our results suggest that the cdc16-183 mutant may have a novel APC/C defect(s) that mimics or activates the spindle checkpoint pathway.
酿酒酵母在中期到后期转换过程中姐妹染色单体的准确分离受后期促进复合物或周期体（APC/C）活性的调控。在纺锤体受损或单极纺锤体附着的情况下，纺锤体检查点被激活，并抑制APC/C对后期抑制因子Pds1p的活性，导致细胞周期在中期停滞。我们在酿酒酵母中鉴定出了一个APC/C亚基基因的新等位基因cdc16-183。cdc16-183突变体在37℃时停滞在中期，并且在较低温度下对激活纺锤体检查点的纺锤体损伤剂诺考达唑超敏感。对诺考达唑的这种超敏感性不能用纺锤体检查点途径的损伤来解释，因为细胞对纺锤体损伤的反应是正常的，会稳定地停滞在中期且Pds1p水平较高。尽管cdc16-183突变体在37℃时在G2/M期停滞在中期，但在这个温度下它们能够正常执行所测试的G1期功能。这是首次证明核心APC/C亚基的突变可导致在限制温度下依赖MAD2的停滞。我们的结果表明，cdc16-183突变体可能存在一种新的APC/C缺陷，该缺陷模拟或激活了纺锤体检查点途径。
