Mutator phenotypes conferred by MLH1 overexpression and by heterozygosity for mlh1 mutations

Polina V. Shcherbakova, Thomas A. Kunkel

Research output: Contribution to journalArticle

140 Citations (Scopus)

Abstract

Loss of DNA mismatch repair due to mutation or diminished expression of the MLH1 gene is associated with genome instability and cancer. In this study, we used a yeast model system to examine three circumstances relevant to modulation of MLH1 function. First, overexpression of wild-type MLH1 was found to cause a strong elevation of mutation rates at three different loci, similar to the mutator effect of MLH1 gene inactivation. Second, haploid yeast strains with any of six mlh1 missense mutations that mimic germ line mutations found in human cancer patients displayed a strong mutator phenotype consistent with loss of mismatch repair function. Five of these mutations affect amino acids that are homologous to residues suggested by recent crystal structure and biochemical analysis of Escherichia coli MutL to participate in ATP binding and hydrolysis. Finally, using a highly sensitive reporter gene, we detected a mutator phenotype of diploid yeast strains that are heterozygous for mlh1 mutations. Evidence suggesting that this mutator effect results not from reduced mismatch repair in the MLH1/mlh1 cells but rather from loss of the wild-type MLH1 allele in a fraction of cells is presented. Exposure to bleomycin or to UV irradiation strongly enhanced mutagenesis in the heterozygous strain but had little effect on the mutation rate in the wild-type strain. This damage-induced hypermutability may be relevant to cancer in humans with germ line mutations in only one MLH1 allele.

Original languageEnglish (US)
Pages (from-to)3177-3183
Number of pages7
JournalMolecular and cellular biology
Volume19
Issue number4
DOIs
StatePublished - Apr 1999

Fingerprint

DNA Mismatch Repair
Germ-Line Mutation
Yeasts
Mutation Rate
Phenotype
Mutation
Alleles
Neoplasms
Genomic Instability
Haploidy
Bleomycin
Gene Silencing
Missense Mutation
Diploidy
Reporter Genes
Mutagenesis
Hydrolysis
Adenosine Triphosphate
Escherichia coli
Gene Expression

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

Cite this

Mutator phenotypes conferred by MLH1 overexpression and by heterozygosity for mlh1 mutations. / Shcherbakova, Polina V.; Kunkel, Thomas A.

In: Molecular and cellular biology, Vol. 19, No. 4, 04.1999, p. 3177-3183.

Research output: Contribution to journalArticle

@article{13f530301f2a46b08a398ec2e8772c65,
title = "Mutator phenotypes conferred by MLH1 overexpression and by heterozygosity for mlh1 mutations",
abstract = "Loss of DNA mismatch repair due to mutation or diminished expression of the MLH1 gene is associated with genome instability and cancer. In this study, we used a yeast model system to examine three circumstances relevant to modulation of MLH1 function. First, overexpression of wild-type MLH1 was found to cause a strong elevation of mutation rates at three different loci, similar to the mutator effect of MLH1 gene inactivation. Second, haploid yeast strains with any of six mlh1 missense mutations that mimic germ line mutations found in human cancer patients displayed a strong mutator phenotype consistent with loss of mismatch repair function. Five of these mutations affect amino acids that are homologous to residues suggested by recent crystal structure and biochemical analysis of Escherichia coli MutL to participate in ATP binding and hydrolysis. Finally, using a highly sensitive reporter gene, we detected a mutator phenotype of diploid yeast strains that are heterozygous for mlh1 mutations. Evidence suggesting that this mutator effect results not from reduced mismatch repair in the MLH1/mlh1 cells but rather from loss of the wild-type MLH1 allele in a fraction of cells is presented. Exposure to bleomycin or to UV irradiation strongly enhanced mutagenesis in the heterozygous strain but had little effect on the mutation rate in the wild-type strain. This damage-induced hypermutability may be relevant to cancer in humans with germ line mutations in only one MLH1 allele.",
author = "Shcherbakova, {Polina V.} and Kunkel, {Thomas A.}",
year = "1999",
month = "4",
doi = "10.1128/MCB.19.4.3177",
language = "English (US)",
volume = "19",
pages = "3177--3183",
journal = "Molecular and Cellular Biology",
issn = "0270-7306",
publisher = "American Society for Microbiology",
number = "4",

}

TY - JOUR

T1 - Mutator phenotypes conferred by MLH1 overexpression and by heterozygosity for mlh1 mutations

AU - Shcherbakova, Polina V.

AU - Kunkel, Thomas A.

PY - 1999/4

Y1 - 1999/4

N2 - Loss of DNA mismatch repair due to mutation or diminished expression of the MLH1 gene is associated with genome instability and cancer. In this study, we used a yeast model system to examine three circumstances relevant to modulation of MLH1 function. First, overexpression of wild-type MLH1 was found to cause a strong elevation of mutation rates at three different loci, similar to the mutator effect of MLH1 gene inactivation. Second, haploid yeast strains with any of six mlh1 missense mutations that mimic germ line mutations found in human cancer patients displayed a strong mutator phenotype consistent with loss of mismatch repair function. Five of these mutations affect amino acids that are homologous to residues suggested by recent crystal structure and biochemical analysis of Escherichia coli MutL to participate in ATP binding and hydrolysis. Finally, using a highly sensitive reporter gene, we detected a mutator phenotype of diploid yeast strains that are heterozygous for mlh1 mutations. Evidence suggesting that this mutator effect results not from reduced mismatch repair in the MLH1/mlh1 cells but rather from loss of the wild-type MLH1 allele in a fraction of cells is presented. Exposure to bleomycin or to UV irradiation strongly enhanced mutagenesis in the heterozygous strain but had little effect on the mutation rate in the wild-type strain. This damage-induced hypermutability may be relevant to cancer in humans with germ line mutations in only one MLH1 allele.

AB - Loss of DNA mismatch repair due to mutation or diminished expression of the MLH1 gene is associated with genome instability and cancer. In this study, we used a yeast model system to examine three circumstances relevant to modulation of MLH1 function. First, overexpression of wild-type MLH1 was found to cause a strong elevation of mutation rates at three different loci, similar to the mutator effect of MLH1 gene inactivation. Second, haploid yeast strains with any of six mlh1 missense mutations that mimic germ line mutations found in human cancer patients displayed a strong mutator phenotype consistent with loss of mismatch repair function. Five of these mutations affect amino acids that are homologous to residues suggested by recent crystal structure and biochemical analysis of Escherichia coli MutL to participate in ATP binding and hydrolysis. Finally, using a highly sensitive reporter gene, we detected a mutator phenotype of diploid yeast strains that are heterozygous for mlh1 mutations. Evidence suggesting that this mutator effect results not from reduced mismatch repair in the MLH1/mlh1 cells but rather from loss of the wild-type MLH1 allele in a fraction of cells is presented. Exposure to bleomycin or to UV irradiation strongly enhanced mutagenesis in the heterozygous strain but had little effect on the mutation rate in the wild-type strain. This damage-induced hypermutability may be relevant to cancer in humans with germ line mutations in only one MLH1 allele.

UR - http://www.scopus.com/inward/record.url?scp=0032915375&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0032915375&partnerID=8YFLogxK

U2 - 10.1128/MCB.19.4.3177

DO - 10.1128/MCB.19.4.3177

M3 - Article

C2 - 10082584

AN - SCOPUS:0032915375

VL - 19

SP - 3177

EP - 3183

JO - Molecular and Cellular Biology

JF - Molecular and Cellular Biology

SN - 0270-7306

IS - 4

ER -