Effect of p53 Genotype on Gene Expression and DNA Adducts in ENU-Exposed Mice

P53, the tumour suppressor protein, plays a crucial role in the maintenance of genomic stability and is regarded as the ‘guardian of the genome’. To study tissue differences in p53 loss-of-function mutations, we investigated the effect of N-ethyl-N-nitrosourea (ENU), a highly potent mutagen, on gene expression at 4 and 24 h after exposure in the liver of p53+/+, p53+/− and p53−/− mice. Quantitative PCR and a targeted array were used to analyse the expression of 84 genes known to be involved in the p53 pathway at each time point. In addition, the levels of O6-ethyldeoxyguanosine, a major mutagenic DNA adduct, and the expression of Mgmt were determined at the 4- and 24-h time points. Significant differences were found among the three genotypes for the expression of the functional gene groupings of apoptosis, cell cycle, cell growth and proliferation and DNA repair. Furthermore, the loss of O6-ethyldeoxyguanosine from the DNA paralleled the expression of Mgmt in p53+/+ and p53+/− mice. The data from this study will aid in understanding variation in the DNA damage response across tissues and the biological effects of loss of function in p53. Keywords: P53; ENU; gene expression; DNA Adducts