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TP53 and lacZ mutagenesis induced by 3-nitrobenzanthrone in Xpa-deficient human TP53 knock-in mouse embryo fibroblasts.

Abstract：

:3-Nitrobenzanthrone (3-NBA) is a highly mutagenic compound and possible human carcinogen found in diesel exhaust. 3-NBA forms bulky DNA adducts following metabolic activation and induces predominantly G:CT:A transversions in a variety of experimental systems. Here we investigated the influence of nucleotide excision repair (NER) on 3-NBA-induced mutagenesis of the human tumour suppressor gene TP53 and the reporter gene lacZ. To this end we utilised Xpa -knockout (Xpa-Null) human TP53 knock-in (Hupki) embryo fibroblasts (HUFs). As Xpa is essential for NER of bulky DNA adducts, we hypothesized that DNA adducts induced by 3-NBA would persist in the genomes of Xpa-Null cells and lead to an increased frequency of mutation. The HUF immortalisation assay was used to select for cells harbouring TP53 mutations following mutagen exposure. We found that Xpa-Null Hupki mice and HUFs were more sensitive to 3-NBA treatment than their wild-type (Xpa-WT) counterparts. However, following 3-NBA treatment and immortalisation, a similar frequency of TP53-mutant clones arose from Xpa-WT and Xpa-Null HUF cultures. In cells from both Xpa genotypes G:CT:A transversion was the predominant TP53 mutation type and mutations exhibited bias towards the non-transcribed strand. Thirty-two percent of 3-NBA-induced TP53 mutations occurred at CpG sites, all of which are hotspots for mutation in smokers' lung cancer (codons 157, 158, 175, 245, 248, 273, 282). We also examined 3-NBA-induced mutagenesis of an integrated lacZ reporter gene in HUFs, where we again observed a similar mutant frequency in Xpa-WT and Xpa-Null cells. Our findings suggest that 3-NBA-DNA adducts may evade removal by global genomic NER; the persistence of 3-NBA adducts in DNA may be an important factor in its mutagenicity.

journal_name

DNA Repair (Amst)

journal_title

DNA repair

authors

Kucab JE,Zwart EP,van Steeg H,Luijten M,Schmeiser HH,Phillips DH,Arlt VM

doi

10.1016/j.dnarep.2015.11.004

subject

Has Abstract

pub_date

2016-03-01 00:00:00

pages

21-33

eissn

1568-7864

issn

1568-7856

pii

S1568-7864(15)30018-5

journal_volume

pub_type

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TP53 and lacZ mutagenesis induced by 3-nitrobenzanthrone in Xpa-deficient human TP53 knock-in mouse embryo fibroblasts.