Page Andrew M, Aneliunas Vicky, Lamb John R, Hieter Philip
Program in Biochemistry, Cellular, and Molecular Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Genetics. 2005 Jul;170(3):1045-62. doi: 10.1534/genetics.104.040105. Epub 2005 May 23.
We have examined the in vivo requirement of two recently identified nonessential components of the budding yeast anaphase-promoting complex, Swm1p and Mnd2p, as well as that of the previously identified subunit Apc9p. swm1Delta mutants exhibit synthetic lethality or conditional synthetic lethality with other APC/C subunits and regulators, whereas mnd2Delta mutants are less sensitive to perturbation of the APC/C. swm1Delta mutants, but not mnd2Delta mutants, exhibit defects in APC/C substrate turnover, both during the mitotic cell cycle and in alpha-factor-arrested cells. In contrast, apc9Delta mutants exhibit only minor defects in substrate degradation in alpha-factor-arrested cells. In cycling cells, degradation of Clb2p, but not Pds1p or Clb5p, is delayed in apc9Delta. Our findings suggest that Swm1p is required for full catalytic activity of the APC/C, whereas the requirement of Mnd2p for APC/C function appears to be negligible under standard laboratory conditions. Furthermore, the role of Apc9p in APC/C-dependent ubiquitination may be limited to the proteolysis of a select number of substrates.
我们研究了芽殖酵母后期促进复合体（APC）两个最近鉴定出的非必需成分Swm1p和Mnd2p以及先前鉴定出的亚基Apc9p在体内的需求情况。swm1Δ突变体与其他APC/C亚基和调节因子表现出合成致死性或条件性合成致死性，而mnd2Δ突变体对APC/C的扰动不太敏感。swm1Δ突变体，而非mnd2Δ突变体，在有丝分裂细胞周期以及α因子阻滞的细胞中，均表现出APC/C底物周转缺陷。相比之下，apc9Δ突变体在α因子阻滞的细胞中仅表现出轻微的底物降解缺陷。在循环细胞中，apc9Δ中Clb2p的降解延迟，但Pds1p或Clb5p的降解未延迟。我们的研究结果表明，Swm1p是APC/C充分催化活性所必需的，而在标准实验室条件下，Mnd2p对APC/C功能的需求似乎可以忽略不计。此外，Apc9p在依赖APC/C的泛素化中的作用可能仅限于少数特定底物的蛋白水解。
