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MUTANT FREQUENCY AND MUTATIONAL SPECTRA IN THETK AND HPRT GENES OF N-ETHYL-N-NITROSOUREA TREATED MOUSE LYMPHOMA CELLS
Citation:
Chen, T., K H. Brock, AND M M. Moore. MUTANT FREQUENCY AND MUTATIONAL SPECTRA IN THETK AND HPRT GENES OF N-ETHYL-N-NITROSOUREA TREATED MOUSE LYMPHOMA CELLS. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 39(4):306-313, (2001).
Description:
Abstract
The mouse lymphoma assay (MLA) utilizing the Tk locus is widely used to identify chemical mutagens. The autosomal location of the Tk locus allows for the detection of a wide range of mutational events, from point mutations to chromosome alterations. However, the chemically induced point mutation spectra in the Tk gene of mouse lymphoma cells has not been characterized. In this study, we determined and compared the mutagenicity and mutational spectra of N-ethyl-N-nitrosourea (ENU) in the Tk and Hprt genes of mouse lymphoma cells. Treatment of L5178Y mouse lymphoma cells with 100 ug/ml ENU induced a Tkmutant frequency of 756 x 10-6 and anHprt mutant frequency of 311 x 10-6. Sequence analysis of Tk and Hprt mutant cDNAs showed a similar overall mutation pattern in the two genes with base pair substitutions accounting for 83% of mutations in the Tk gene and 75% in the Hprt gene. The most common point mutation induced by ENU was G:C -> A:T transition (36% and 28% of total independent point mutations in the Tk and Hprt genes, respectively). The mutation spectra induced by ENU in both the Tk and Hprt genes were different from the respective patterns produced in mutants from untreated cells. About 9% of Tk and 7% of Hprt mutations from control cells were in-frame deletions, whereas no such mutations were found among the ENU-induced Tk and Hprt mutations. Our results indicated that ENU produces a chemical-specific point mutational profile in the Tk gene of mouse lymphoma cells that is remarkably similar to that found in the X-linked Hprt gene. This study provides evidence that the MLA can be used not only to detect point mutagens but also for analysis of mutational spectra.
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