Functional analysis of human MLH1 and MSH2 missense variants and hybrid human-yeast MLH1 proteins in Saccharomyces cerevisiae
Functional analysis of human MLH1 and MSH2 missense variants and hybrid human-yeast MLH1 proteins in Saccharomyces cerevisiae
复制标题
DOI：
10.1093/hmg/10.18.1889
复制
发表时间：
2001-09-01
影响因子：
3.5
通讯作者：
Bitter, GA
中科院分区：
文献类型：
--
作者：
Ellison, AR;Lofing, J;Bitter, GA
遗传性非息肉病性结直肠癌（Hereditary non-polyposis colorectal cancer，HNPCC）是一种由DNA错配修复（DNA mismatch repair，MMR）过程缺陷引起的常染色体显性遗传疾病，大多数HNPCC是由hMLH 1或hMSH 2基因突变引起的。除了由编码序列中的无义或移码改变或剪接变体赋予的明确的功能丧失突变之外，遗传筛选还揭示了大量具有不太明显的功能后果的错义密码子。区分功能丧失突变和沉默多态性的能力对于遗传性疾病（如HNPCC）的基因检测非常重要，因为HNPCC有机会进行早期诊断和预防性干预。在这项研究中，在酵母酿酒酵母中进行定量体内DNA MMR测定，以确定在人群中观察到的氨基酸替换的功能意义。在酵母hMLH 1或MSH 2基因的同源残基上引入了以前在人类基因中观察到的错义密码子。本研究还证明了构建编码功能性杂合体人-酵母MLH 1蛋白的基因的可行性。发现三类错义密码子：（i）功能完全丧失，即突变;（ii）与野生型蛋白质不可区分的变体，即沉默多态性;和（iii）以降低的效率支持MMR的功能变体，即效率多态性。在酵母中的功能结果与关于错义密码子的突变的可用人类临床数据之间存在良好的相关性。本文报道的结果提出了一种有趣的可能性，即由于共同的多态性，人类群体中个体之间存在DNA MMR效率的差异。
Hereditary non-polyposis colorectal cancer (HNPCC) is an autosomal dominant inherited disease caused by defects in the process of DNA mismatch repair (MMR), and mutations in the hMLH1 or hMSH2 genes are responsible for the majority of HNPCC. In addition to clear loss-of-function mutations conferred by nonsense or frameshift alterations in the coding sequence or by splice variants, genetic screening has revealed a large number of missense codons with less obvious functional consequences. The ability to discriminate between a loss-of-function mutation and a silent polymorphism is important for genetic testing for inherited diseases like HNPCC where the opportunity exists for early diagnosis and preventive intervention. In this study, quantitative in vivo DNA MMR assays in the yeast Saccharomyces cerevisiae were performed to determine the functional significance of amino acid replacements observed in the human population. Missense codons previously observed in human genes were introduced at the homologous residue in the yeast hMLH1 or MSH2 genes. This study also demonstrated feasibility of constructing genes that encode functional hybrid human-yeast MLH1 proteins. Three classes of missense codons were found: (i) complete loss of function, i.e. mutations; (ii) variants indistinguishable from wild-type protein, i.e. silent polymorphisms; and (iii) functional variants which support MMR at reduced efficiency, i.e. efficiency polymorphisms. There was a good correlation between the functional results in yeast and available human clinical data regarding penetrance of the missense codon. The results reported here raise the intriguing possibility that differences in the efficiency of DNA MMR exist between individuals in the human population due to common polymorphisms.