ULTRAVIOLET LIGHT-INDUCED DNA SEQUENCE CHANGES IN A CHLORAMPHENICOL RESISTANCE GENE IN E. COLI CELLS

Abstract

We analyzed the DNA sequence changes in UV-induced mutagenesis of a chloramphenicol resistance gene of E. coli which was cloned on a plasmid. Both base change and frameshift mutations were observed after UV irradiation of the plasmid DNA. In base change mutations, GC to AT transitions were predominant. They appeared at the 3′C of 5′-Pyr-C-3′ sequences. This supports the hypothesis that the Pyr(6, 4)Pyo product is the main cause of UV-induced base-change mutations. Frameshift mutations with single-base deletion or insertion were found at sequences where the AT base pairs were repeated. This indicates that pyrimidine dimers induce frameshift mutations.