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首页> 外文期刊>Molecular and Cellular Biology >SCS1, a multicopy suppressor of hsp60-ts mutant alleles, does not encode a mitochondrially targeted protein.
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SCS1, a multicopy suppressor of hsp60-ts mutant alleles, does not encode a mitochondrially targeted protein.

机译：SCS1，hsp60-ts突变等位基因的多拷贝抑制剂，不编码线粒体靶向蛋白。

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We identified and isolated a Saccharomyces cerevisiae gene which, when overexpressed, suppressed the temperature-sensitive phenotype of cells expressing a mutant allele of the gene encoding the mitochondrial chaperonin, Hsp60. This gene, SCS1 (suppressor of chaperonin sixty-1), encodes a 757-amino-acid protein of as yet unknown function which, nonetheless, has human, rice, and Caenorhabditis elegans homologs with high degrees (ca. 60%) of amino acid sequence identity. SCS1 is not an essential gene, but SCS1-null strains do not grow above 37 degrees C and show some growth-related defects at 30 degrees C as well. This gene is expressed at both 30 and 38 degrees C, producing little or no differences in mRNA levels at these two temperatures. Overexpression of SCS1 could not complement an HSP60-null allele, indicating that suppression was not due to the bypassing of Hsp60 activity. Of 10 other hsp60-ts alleles tested, five could also be suppressed by SCS1 overexpression. There were no common mutant phenotypes of the strains expressing these alleles that give any clue as to why they were suppressible while others were not. An epitope (influenza virus hemagglutinin)-tagged form of SCS1 in single copy complemented an SCS1-null allele. The Scs1-hemagglutinin protein was found to be at comparable levels and in similar multiply modified forms in cells growing at both 30 and 38 degrees C. Surprisingly, when localized either by cell fractionation procedures or by immunocytochemistry, these proteins were found not in mitochondria but in the cytosol. The overexpression of SCS1 had significant effects on the cellular levels of mRNAs encoding the proteins Cpn10 and Mgel, two other mitochondrial protein cochaperones, but not on mRNAs encoding a number of other mitochondrial or cytosolic proteins analyzed. The implications of these findings are discussed.
机译：我们鉴定并分离了酿酒酵母基因，该基因在过度表达时能抑制表达线粒体伴侣蛋白Hsp60基因突变等位基因的细胞的温度敏感性表型。该基因SCS1（伴侣蛋白60-1的抑制剂）编码一个功能未知的757个氨基酸蛋白质，尽管如此，它具有人类，水稻和秀丽隐杆线虫的同源性，其氨基酸高度（约60％）酸序列同一性。 SCS1不是必需的基因，但无SCS1的菌株不会在37摄氏度以上生长，并且在30摄氏度时也会显示一些与生长相关的缺陷。该基因在30和38摄氏度下表达，在这两个温度下mRNA水平几乎没有差异。 SCS1的过表达不能补充HSP60-null等位基因，表明抑制不是由于绕过Hsp60活性。在测试的其他10个hsp60-ts等位基因中，有5个也可以被SCS1过表达抑制。表达这些等位基因的菌株没有常见的突变表型，这些突变表型提供了为什么它们可被抑制而另一些却不能被抑制的线索。单拷贝的SCS1的表位（流感病毒血凝素）标记形式补充了SCS1空等位基因。发现在30和38摄氏度下生长的细胞中，Scs1-血凝素蛋白处于可比较的水平，并且具有相似的多重修饰形式。令人惊讶的是，当通过细胞分级分离程序或通过免疫细胞化学进行定位时，发现这些蛋白不在线粒体中，而是在线粒体中。在细胞质中SCS1的过表达对编码蛋白Cpn10和Mgel，其他两种线粒体蛋白伴侣蛋白的mRNA的细胞水平具有显着影响，但对编码许多其他分析的线粒体或胞质蛋白的mRNA则没有影响。讨论了这些发现的含义。

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