Murina O A, Moskalenko S E, Zhuravleva G A
Mol Biol (Mosk). 2010 Mar-Apr;44(2):301-10.
The variety of mechanisms providing viability of organisms bearing nonsense-mutations in the essential genes is unknown at present. In yeast Saccharomyces cerevisiae nonsense-mutants containing premature stop-codon in mRNA of the essential SUP45 gene were obtained. These strains are viable in the absence of mutant suppressor tRNA, therefore it is supposed that there are alternative mechanisms providing nonsense-suppression and mutants viability. Analysis of transformants obtained by transformation of strain bearing nonsense-mutant allele of SUP45 gene with multicopy yeast genomic library revealed three genes encoding wild type tRNA(Tyr) and four genes encoding wild type tRNA(Gln) that improve nonsense-mutants viability. Moreover, overexpression of these genes leads to the increase in the amount of full-length eRF1 protein in cell and compensates nonsense-mutants sensitivity to high temperature. Probable mechanisms of tRNA(Tyr) and tRNA(Gln) influence on the increase of viability of nonsense-mutants in SUP45 gene are discussed in this work.
目前尚不清楚在必需基因中携带无义突变的生物体保持生存能力的多种机制。在酿酒酵母中，获得了在必需的SUP45基因的mRNA中含有过早终止密码子的无义突变体。这些菌株在没有突变抑制tRNA的情况下仍能存活，因此推测存在提供无义抑制和突变体生存能力的替代机制。用多拷贝酵母基因组文库转化携带SUP45基因无义突变等位基因的菌株所获得的转化体分析表明，有三个基因编码野生型tRNA（Tyr）和四个基因编码野生型tRNA（Gln），它们可提高无义突变体的生存能力。此外，这些基因的过表达导致细胞中全长eRF1蛋白量的增加，并补偿无义突变体对高温的敏感性。本文讨论了tRNA（Tyr）和tRNA（Gln）影响SUP45基因无义突变体生存能力增加的可能机制。
