Diet- and age-dependent modulation of O6-methylguanine-DNA methyltransferase levels in mouse tissues

Methylation of guanine in the O6 position by N-nitrosodimethylamine is higher in liver DNA of mice fed a diet restricted in essential amino acids than in controls. A diminished content of the repair enzyme O6-methylguanine-DNA methyltransferase (AAT) may be responsible for the elevated level of O6-methylguanine observed after amino acid deficiency. A delayed repair of O6-methylguanine can be ascribed to diminished AAT activity in amino-acid-restricted mice. In adults, but not in subadults, the diminished AAT activity in liver correlated well with a 40% decrease in overall protein synthesis.