A highly purified phenylalanine transfer RNA (tRNAPhe) was isolated from normal rat liver and from livers of male and female rats fed a semisynthetic diet containing 0.06% 3′-methyl-4-dimethylaminoazobenzene for 3 weeks. Absorption spectral analysis on tRNAPhe from normal and carcinogen-fed rats indicated an unusual absorption above 335 nm by tRNAPhe isolated from the latter group. Ribonuclease T1 digestion followed by chromatography on diethylaminoethyl cellulose columns indicated the existence of a major peak of covalently bound oligonucleotide-azo complex. Microcrystalline cellulose thin-layer chromatography resolved the peak into one major and four minor components, all with similar absorption spectra. Enzymatic digestion of the major peak obtained from diethylaminoethyl cellulose chromatography to ribonucleosides, followed by chromatography on cellulose thin layer, resulted in one major and three minor components. A higher uridine:cytidine base ratio was also observed in the tRNAPhe isolated from the carcinogenfed animals. These findings suggest that certain transfer RNA's may be major targets for this azo carcinogen.
Supported by Grants from the American Cancer Society and The Robert A. Welch Foundation (G-035).