Effect of nucleotide substitutions in N-acetyltransferase-1 on N-acetylation (deactivation) and O-acetylation (activation) of arylamine carcinogens: implications for cancer predisposition

Genetic polymorphism in N-acetyltransferase-1 (NAT1) is associated with increased risk of various cancers, but epidemiological investigations are compromised by poor understanding of the relationship between NAT1 genotype and phenotype. Human reference NAT1∗4 and 12 known human NAT1 allelic variants possessing nucleotide polymorphisms in the NAT1 coding region were cloned and expressed in yeast (Schizosaccharomyces pombe). Large reductions in the N-acetylation of 4-aminobiphenyl and the O-acetylation of N-hydroxy-2-aminofluorene were observed for recombinant NAT1 allozymes encoded by NAT1∗14B, NAT1∗15, NAT1∗17, NAT1∗19, and NAT1∗22. Each of these alleles exhibited substantially lower expression of NAT1 protein than the reference NAT1∗4 and the other NAT1 alleles. These results show an important effect of the NAT1 genetic polymorphism on the N- and O-acetylation of arylamine carcinogens, suggesting modification of cancer susceptibility following exposures to arylamine carcinogens.