Small Toxic Protein Encoded on Chromosome VII of Saccharomyces cerevisiae

In a previous study, we found an unknown element that caused growth inhibition after its copy number increased in the 3′ region of DIE2 in Saccharomyces cerevisiae. In this study, we further identified this element and observed that overexpression of a small protein (sORF2) of 57 amino acids encoded in this region caused growth inhibition. The transcriptional response and multicopy suppression of the growth inhibition caused by sORF2 overexpression suggest that sORF2 overexpression inhibits the ergosterol biosynthetic pathway. sORF2 was not required in the normal growth of S. cerevisiae, and not conserved in related yeast species including S. paradoxus. Thus, sORF2 (designated as OTO1) is an orphan ORF that determines the specificity of this species.在既往研究中，我们于酿酒酵母（Saccharomyces cerevisiae）的DIE2基因3′区域发现了一种未知元件，当其拷贝数升高时会引发生长抑制。本研究中，我们进一步鉴定了该元件，并观察到该区域编码的、由57个氨基酸组成的小蛋白（sORF2）过表达会导致生长抑制。针对sORF2过表达引发的生长抑制所开展的转录响应分析与多拷贝抑制实验结果表明，sORF2过表达会抑制麦角固醇生物合成途径。sORF2并非酿酒酵母正常生长所必需，且在包括帕拉酵母（Saccharomyces paradoxus）在内的相关酵母物种中均无保守性。综上，sORF2（命名为OTO1）是一种决定该物种特异性的孤儿开放阅读框。