Coding properties of ultraviolet photoproducts of uracil: II. Phenotypic reversion of the amber mutation: Implication of the uracil hydrate

Abstract

We have observed ultraviolet-induced phenotypic reversion of an amber mutation in vivo, a phenomenon predicted on the basis of studies in vitro of code changes brought about by ultraviolet irradiation of the RNA base uracil. Mathematical analysis indicated that the rate of production of reversion by ultraviolet light is of the same magnitude as the rate of production of uracil hydrate upon irradiation of poly U. Furthermore, the results lead to the conclusion that an amino acid with codon containing a uracil hydrate can be added to the growing polypeptide chain in vivo. Moreover, protein synthesis can proceed past this ultraviolet lesion.