An alkylation-tolerant, mutator human cell line is deficient in strand-specific mismatch repair.

Journal Article (Journal Article)

The human lymphoblastoid MT1 B-cell line was previously isolated as one of a series of mutant cells able to survive the cytotoxic effects of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). MT1 cells nevertheless remain sensitive to mutagenesis by MNNG and display a mutator phenotype. These phenotypes have been attributed to a single genetic alteration postulated to confer a defect in strand-specific mismatch repair, a proposal that attributes the cytotoxic effect of DNA alkylation in wild-type cells to futile attempts to correct mispairs that arise during replication of alkylated template strands. Our results support this view. MNNG-induced mutations in the HPRT gene of MT1 cells are almost exclusively G.C-->A.T transitions, while spontaneous mutations observed in this mutator cell line are single-nucleotide insertions, transversions, and A.T-->G.C transitions. In vitro assay has demonstrated that the MT1 line is in fact deficient in strand-specific correction of all eight base-base mispairs. This defect, which is manifest at or prior to the excision stage of the reaction, is due to simple deficiency of a required activity because MT1 nuclear extracts can be complemented by a partially purified HeLa fraction to restore in vitro repair. These findings substantiate the idea that strand-specific mismatch repair contributes to alkylation-induced cytotoxicity and imply that this process serves as a barrier to spontaneous transition, transversion, and insertion/deletion mutations in mammalian cells.

Full Text

Duke Authors

Cited Authors

  • Kat, A; Thilly, WG; Fang, WH; Longley, MJ; Li, GM; Modrich, P

Published Date

  • July 15, 1993

Published In

Volume / Issue

  • 90 / 14

Start / End Page

  • 6424 - 6428

PubMed ID

  • 8341649

Pubmed Central ID

  • PMC46944

International Standard Serial Number (ISSN)

  • 0027-8424

Digital Object Identifier (DOI)

  • 10.1073/pnas.90.14.6424


  • eng

Conference Location

  • United States