The effect of genetic background on the function of Saccharomyces cerevisiae mlh1 alleles that correspond to HNPCC missense mutations.
The effect of genetic background on the function of Saccharomyces cerevisiae mlh1 alleles that correspond to HNPCC missense mutations.
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DOI：
10.1093/hmg/ddl479
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发表时间：
2007-02
影响因子：
3.5
通讯作者：
Jennifer J. Wanat;Nikhil Singh;E. Alani
中科院分区：
文献类型：
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作者：
Jennifer J. Wanat;Nikhil Singh;E. Alani
DNA错配修复（MMR）基因MLH 1的种系突变与大部分遗传性非息肉病性结直肠癌相关。在MLH 1中有大约250种已知的人类突变。其中，三分之一是错义变体，通常难以表征致病性。我们分析了面包酵母MLH 1的28个等位基因，这些等位基因对应于在线HNPCC数据库中列出的非截短人类突变等位基因，其中13个先前未在功能测定中进行过研究。使用高灵敏度的lys 2：：InsE-A（14）回复率测定法，我们确定了酿酒酵母S288 c菌株中每个等位基因赋予的MMR能力。7个等位基因赋予无效表型的MMR和其他8个表现出显着的MMR缺陷，这表明所有15个可能是人类的致病性。此外，我们观察到这些结果之间的强相关性，来自先前功能测定和临床数据的有限结果。为了测试某些等位基因的潜在致病性是否取决于宿主的遗传背景，我们研究了第二种酵母菌株SK 1中mlh 1等位基因所赋予的突变率，SK 1与S288 c的差异约为0.7%。许多等位基因表现出不同菌株背景之间的MMR效率差异，随着MMR缺陷严重程度的增加，差异逐渐减小。这些发现表明，遗传背景可以发挥重要作用，在确定致病性的MMR等位基因，并可能解释非典型大肠癌遗传的情况下。
Germline mutations in the DNA mismatch repair (MMR) gene MLH1 are associated with a large percentage of hereditary non-polyposis colorectal cancers. There are approximately 250 known human mutations in MLH1. Of these, one-third are missense variants that are often difficult to characterize with regards to pathogenicity. We analysed 28 alleles of baker's yeast MLH1 that correspond to non-truncating human mutant alleles listed in online HNPCC databases, 13 of which had not been previously studied in functional assays. Using the highly sensitive lys2::InsE-A(14) reversion rate assay, we determined the MMR proficiency conferred by each allele in the S288c strain of Saccharomyces cerevisiae. Seven alleles conferred a null phenotype for MMR and eight others showed significant MMR defects, suggesting that all 15 are likely to be pathogenic in humans. In addition, we observed a strong correlation between these results, limited results from previous functional assays and clinical data. To test whether the potential pathogenicity of certain alleles depends on the genetic background of the host, we examined the mutation rates conferred by the mlh1 alleles in a second yeast strain, SK1, which is approximately 0.7% divergent from S288c. Many alleles displayed a difference in MMR efficiency between strain backgrounds with decreasing differences as the severity of the MMR defect increased. These findings suggest that genetic background can play an important role in determining the pathogenicity of MMR alleles and may explain cases of atypical colorectal cancer inheritance.