PMID:11555625

Citation	Ellison, AR, Lofing, J and Bitter, GA (2001) Functional analysis of human MLH1 and MSH2 missense variants and hybrid human-yeast MLH1 proteins in Saccharomyces cerevisiae. Hum. Mol. Genet. 10:1889-900
Abstract	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 MLH1 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.
Links	PubMed
Keywords	Adaptor Proteins, Signal Transducing; Amino Acid Sequence; Base Pair Mismatch; Carrier Proteins; DNA Repair; DNA-Binding Proteins; Gene Frequency; Humans; Molecular Sequence Data; MutS Homolog 2 Protein; Mutagenesis, Site-Directed; Mutation, Missense; Neoplasm Proteins/genetics; Neoplasm Proteins/physiology; Nuclear Proteins; Plasmids/genetics; Proto-Oncogene Proteins/genetics; Proto-Oncogene Proteins/physiology; Recombinant Fusion Proteins/genetics; Saccharomyces cerevisiae/genetics; Sequence Homology, Amino Acid
edit table

Annotations

Gene product	Qualifier	GO ID	GO term name	Evidence Code	with/from	Aspect	Notes	Status
edit table

References

See Help:References for how to manage references in GONUTS.