Friedman H, Snyder M
Department of Biology, Yale University, New Haven, CT 06511.
Proc Natl Acad Sci U S A. 1994 Mar 15;91(6):2031-5. doi: 10.1073/pnas.91.6.2031.
Proteasomes are ubiquitous complexes exhibiting proteolytic activity in vitro. The function(s) of these enzymes in vivo is not known. To investigate the in vivo role of proteasomes, four temperature-sensitive alleles of the Saccharomyces cerevisiae proteasome-related gene, PRG1, were constructed and analyzed. At both the permissive and restrictive temperatures, many prg1 cells have a large bud, contain replicated DNA, and have their nucleus positioned at the neck with a short spindle. These different phenotypes indicate a defect in nuclear division. Consistent with a nuclear division defect, prg1 mutant strains lose a dispensable chromosome at a higher frequency than wild-type cells. Importantly, deletion of CLB2, a gene encoding a mitotic cyclin, suppresses the temperature-sensitive growth phenotype of prg1 mutant strains. Our results indicate that proteasomes are important for nuclear division and suggest that they participate in degradation of the Clb2 protein (Clb2p).
蛋白酶体是在体外具有蛋白水解活性的普遍存在的复合物。这些酶在体内的功能尚不清楚。为了研究蛋白酶体在体内的作用，构建并分析了酿酒酵母蛋白酶体相关基因PRG1的四个温度敏感等位基因。在允许温度和限制温度下，许多prg1细胞都有一个大芽，含有复制的DNA，并且细胞核位于颈部，纺锤体较短。这些不同的表型表明核分裂存在缺陷。与核分裂缺陷一致，prg1突变菌株比野生型细胞以更高的频率丢失一条可有可无的染色体。重要的是，编码有丝分裂周期蛋白的基因CLB2的缺失抑制了prg1突变菌株的温度敏感生长表型。我们的结果表明蛋白酶体对核分裂很重要，并表明它们参与Clb2蛋白（Clb2p）的降解。
