The effect of N-nitroso carcinogens and triazenes on protein synthesis in cell-free systems

The effect of a series of carcinogenic nitrosamines, alkylnitrosoureas and alkaryltriazenes on enzymatic reactions involved in protein synthesis was studied in cell-free systems from rat liver. The addition of most compounds stimulated the formation of aminoacyl-tRNA complex in test systems from rat liver whereas analogous preparations from Escherichia coli did not show this effect. The polymerization of phenylalanine and the binding of aminoacyl-tRNA to ribosome were only slightly and apparently non-specifically inhibited in the presence of the test compounds. On the other hand, the binding of nRNA to ribosome was markedly stimulated after the addition of most carcinogens tested. It appears that the carcinogens intervene specifically with one of the early steps in peptide initiation. Since the binding of mRNA to ribosome is known to be an important rate-limiting step in protein synthesis, the N-nitroso carcinogens and triazenes may thus control the expression of genetic message at the translation level.