Fujimura T, Wickner R B
Mol Cell Biol. 1986 Feb;6(2):404-10. doi: 10.1128/mcb.6.2.404-410.1986.
pet18 mutations in Saccharomyces cerevisiae confer on the cell the inability to maintain either L-A or M double-stranded RNAs (dsRNAs) at the nonpermissive temperature. In in vitro experiments, we examined the effects of pet18 mutations on the RNA-dependent RNA polymerase activity associated with virus-like particles (VLPs). pet18 mutations caused thermolabile RNA polymerase activity of L-A VLPs, and this thermolability was found to be due to the instability of the L-A VLP structure. The pet18 mutations did not affect RNA polymerase activity of M VLPs. Furthermore, the temperature sensitivity of wild-type L-A RNA polymerase differed substantially from that of M RNA polymerase. From these results, and from other genetic and biochemical lines of evidence which suggest that replication of M dsRNA requires the presence of L-A dsRNA, we propose that the primary effect of the pet18 mutation is on the L-A VLP structure and that the inability of pet18 mutants to maintain M dsRNA comes from the loss of L-A dsRNA.
酿酒酵母中的pet18突变使细胞在非允许温度下无法维持L-A或M双链RNA（dsRNA）。在体外实验中，我们研究了pet18突变对与病毒样颗粒（VLP）相关的RNA依赖性RNA聚合酶活性的影响。pet18突变导致L-A VLP的RNA聚合酶活性不耐热，并且发现这种热不稳定性是由于L-A VLP结构的不稳定性。pet18突变不影响M VLP的RNA聚合酶活性。此外，野生型L-A RNA聚合酶的温度敏感性与M RNA聚合酶的温度敏感性有很大差异。根据这些结果，以及其他遗传和生化证据表明M dsRNA的复制需要L-A dsRNA的存在，我们提出pet18突变的主要影响是对L-A VLP结构，并且pet18突变体无法维持M dsRNA是由于L-A dsRNA的丧失。
