Molecular characterization of mutations in the hprt gene of normal human skin keratinocytes treated with N-ethyl-N-nitrosourea: Influence of O6-alkylguanine alkyltransferase
✍ Scribed by Hua Hua Tong; Jeong Hae Park; Tonya Brady; Christopher M. Weghorst; Steven M. D`Ambrosio
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 116 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0893-6692
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✦ Synopsis
O 6 -Alkylguanine-DNA alkyltransferase (AGT) is re-group (14/31) was twice that in the group treated sponsible for repairing the O 6 -alkylguanine lesion with ENU alone, consistent with the loss of AGT in DNA. There is wide variation in the levels of AGT activity in these cells. There was no strand specibetween organ and cell types, which appears to ficity of GC to AT and AT to GC transitions in both correlate with cell and tissue type sensitivity to the groups. Base transversions accounted for 28% of mutagenic and carcinogenic effects of alkylating total base substitutions. A lower than expected agents. In order to investigate the role of AGT in proportion of AT to TA transversions were obmodulating the frequency and types of mutations served in both cell lines, which decreased in the induced in one type of normal human parenchymal O 6 -BZ pretreated group. A strand bias was obcells, we examined the types and frequency of muta-served for GC to TA and AT to TA transversions. tions in the hypoxanthine (guanine) phosphoribosyl-Most of the G to A and G to T base substitutions transferase (hprt) gene in 116 mutants derived from had one or more purines flanking 3 to the mutated two N-ethyl-N-nitrosourea (ENU)-treated normal hu-deoxyguanosines. There were more deletion muman skin keratinocyte cell lines. O 6 -Benzylguanine tants with the deletion of exon 1, 4, 6, and 8 in (O 6 -BZ; 5 mM 1 2 hours) was used to specifically the BZ group than in the control group. These data, inhibit AGT activity before ENU treatment (0 to 5 characterizing the mutational spectra of ENU in mM 1 1 hour). O 6 -BZ increased both the cytotoxic normal human keratinocytes treated in vitro, indiand mutagenic effects of ENU by 1.8-and 3-to 5-cate that GC to AT and AT to GC transition mutafold, respectively. In both treatment groups, most of tions predominate in these cells depleted or not the mutations were base substitutions (72%). The depleted of AGT. Environ. Mol. Mutagen. 29: proportion of GC to AT transitions in the O 6 -BZ 168 -179, 1997