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HGPRT- mutants of V79 cells that revert specifically by base pair substitution and frameshift mutations
Abstract:
In order to determine the mutagenic specificity of mutagenic and carcinogenic agents in mammalian cells, a reversion system capable of distinguishing between frameshift mutations and various kinds of base pair substitutions would be useful. We report here a method for the isolation and characterization of HGPRT- Chinese hamster V79 cell mutants that might form the basis for such a system. Two mutants of different specificity have been partially characterized. DEW-1, isolated following N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment, is revertible by the base pair substitution mutagens MNNG and ethyl methanesulfonate (EMS), but not by frameshift mutagens. DSW-3, isolated following ICR-191 treatment, is specifically reverted by frameshift mutagens, but not by EMS or MNNG. With the further characterization of these and other mutants, it should be feasible to determine not only whether an agent is mutagenic in V79 cells, but also to determine the type(s) of mutation(s) it produces.
Insights
Researchers developed a new cell system to identify mutagenic and carcinogenic agents. This system distinguishes between frameshift mutations and base pair substitutions in mammalian cells.
Area of Science:
- Mammalian cell genetics
- Mutagenesis research
- Toxicology
Background:
- Determining the mutagenic specificity of chemical agents is crucial for assessing their carcinogenic potential.
- Existing reversion systems often lack the ability to differentiate between various mutation types, limiting their utility.
Purpose of the Study:
- To develop and characterize a novel reversion system in Chinese hamster V79 cells.
- To create a method for distinguishing between frameshift mutations and base pair substitutions induced by mutagens.
Main Methods:
- Isolation and characterization of hypoxanthine-guanine phosphoribosyltransferase-deficient (HGPRT-) Chinese hamster V79 cell mutants.
- Treatment of cells with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and ICR-191 to induce mutations.
- Testing mutant revertibility using base pair substitution mutagens (MNNG, ethyl methanesulfonate) and frameshift mutagens.
Main Results:
- Two distinct mutants, DEW-1 and DSW-3, were partially characterized.
- DEW-1 reverts via base pair substitutions (MNNG, EMS) but not frameshift mutations.
- DSW-3 specifically reverts via frameshift mutations, not base pair substitutions (MNNG, EMS).
Conclusions:
- The characterized HGPRT- V79 cell mutants form the basis of a system to determine mutagenic specificity.
- This system can differentiate between frameshift and base pair substitution mutations.
- Further characterization will enable the identification of mutagenic agents and the types of mutations they produce in mammalian cells.