ENDONUCLEOLYTIC INCISION OF UVB‐IRRADIATED DNA

Publisher Website
Google Scholar
Abstract
Ultraviolet irradiation of DNA produces a variety of pyrimidine damage. In addition to the well‐known photoproducts, pyrimidine dimers and 6‐4′(pyrimidin‐2'one)pyrimidines, DNA sequence analysis has shown that E. coli endonuclease III incises broad‐spectrum UV‐irradiated DNA at cytosines. The same enzyme incises DNA oxidized by osmium tetroxide at damaged thymines. The wavelength dependence of endonuclease III incision of irradiated DNA was examined. DNA substrates were irradiated by monochromatic light ranging from 250 to 320 nm. Maximal enzymic cleavage was obtained with substrates irradiated by wavelengths between 265 and 285 nm, with peak activity against DNA irradiated at 280 nm. Therefore, these photoproducts are optimally formed at biologically significant wavelengths and may be involved in actinic carcinogenesis.