An alkylation-tolerant, mutator human cell line is deficient in strand-specific mismatch repair
- Massachusetts Institute of Technology, Cambridge (United States)
- Duke Univ. Medical Center, Durham, NC (United States)
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 GC [yields] AT transitions, while spontaneous mutations observed in this mutator cell line are single-nucleotide insertions, transversions, and AT [yields] GC 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. 22 refs., 3 figs., 1 tab.
- OSTI ID:
- 5957247
- Journal Information:
- Proceedings of the National Academy of Sciences of the United States of America; (United States), Vol. 90:14; ISSN 0027-8424
- Country of Publication:
- United States
- Language:
- English
Similar Records
Analysis of forward mutations induced by N-methyl-N'-nitro-N-nitrosoguanidine in the bacteriophage P22 mnt repressor gene
Human tumor strains defective in the repair of alkylated DNA fail to regenerate rapidly-sedimenting nucleoids after N-methyl-N'-nitro-N-nitrosoguanidine treatment
Related Subjects
ANIMAL CELLS
MUTAGENESIS
DNA
ALKYLATION
DNA MISMATCH
DNA REPAIR
DEFECTS
GUANIDINES
GENETIC EFFECTS
SPONTANEOUS MUTATIONS
BIOLOGICAL EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CARBONIC ACID DERIVATIVES
CHEMICAL REACTIONS
MUTATIONS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
REPAIR
550400* - Genetics
550200 - Biochemistry