A functional assay for mutations in tumor suppressor genes caused by mismatch repair deficiency.
The coding sequences of multiple human tumor suppressor genes include microsatellite sequences that are prone to mutations. Saccharomyces cerevisiae strains deficient in DNA mismatch repair (MMR) can be used to determine de novo mutation rates of these human tumor suppressor genes as well as any other gene sequence. Microsatellites in human TGFBR2, PTEN and APC genes were placed in yeast vectors and analyzed in isogenic yeast strains that were wild-type or deletion mutants for MSH2 or MLH1. In MMR-deficient strains, the vector containing the (A)(10) microsatellite sequence of TGFBR2 had a mutation rate (mutations/cell division) of 1.4 x 10(-4), compared to a mutation rate of 1.7 x 10(-6) in the wild-type strain. In MMR-deficient strains, mutation rates in PTEN and APC were also elevated above background levels. PTEN mutation rates were higher in both msh2 (4.4 x 10-5) and mlh1 strains (2.3 x 10-5). APC mutation rates in the msh2 strain (2.4 x 10-6) and the mlh1 strain (1.7 x 10-6) were also significantly, but less dramatically, elevated over background. Mutations selected for in the yeast screen were identical to those previously observed in human tumor samples with microsatellite instability (MSI). This functional assay has applicability in providing quantitative data about microsatellite mutation rates caused by MMR deficiency in any human tumor suppressor gene sequence. It can also be applied as a genetic screen to identify new genes that are vulnerable to such microsatellite mutations and thus may be involved in the neoplastic development of tumors with MSI.
Ji
H P
HP
Department of Medicine, Division of Medical Genetics, University of Washington, Seattle, WA 98195-7720, USA.
King
M C
MC
D048868:Adaptor Proteins, Signal Transducing; D025601:Adenomatous Polyposis Coli Protein / Q000235:genetics; D001681:Biological Assay; D004252:DNA Mutational Analysis / Q000379:methods*; D004260:DNA Repair / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D016147:Genes, Tumor Suppressor; D006801:Humans; D018895:Microsatellite Repeats; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009154:Mutation; D051059:PTEN Phosphohydrolase; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics; D010957:Plasmids; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D025521:Tumor Suppressor Proteins / Q000235:genetics
D048868:Adaptor Proteins, Signal Transducing; D025601:Adenomatous Polyposis Coli Protein; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C088859:MLH1 protein, S cerevisiae; D018125:Receptors, Transforming Growth Factor beta; D029701:Saccharomyces cerevisiae Proteins; D025521:Tumor Suppressor Proteins; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D010744:Phosphoric Monoester Hydrolases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; C489751:MSH2 protein, S cerevisiae; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein