The DNA damage spectrum produced by simulated sunlight

J Mol Biol. 2000 Jun 9;299(3):681-93. doi: 10.1006/jmbi.2000.3771.


The mutagenic effects of ultraviolet and solar irradiation are thought to be due to the formation of DNA photoproducts, most notably cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts ((6-4)PPs). Experimental systems for determining the levels and sequence dependence of photoproduct formation in DNA have often used high doses of short-wave (UVC) irradiation. We have re-assessed this issue by using DNA sequencing technologies and different doses of UVC as well as more physiologically relevant doses of solar irradiation emitted from a solar UV simulator. It has been questioned whether hot alkali treatment can detect (6-4)PPs at all sequence positions. With high UVC doses, the sequence distribution of (6-4)PPs was virtually identical when hot alkali or UV damage endonuclease (UVDE) were used for detection, which appears to validate both methods. The (6-4)PPs form at 5'-TpC and 5'CpC sequences but very low levels are seen at all other dipyrimidines including 5'-TpT. Contrary to expectation, we find that (6-4) photoproducts form at almost undetectable levels under conditions of irradiation for up to five hours with the solar UV simulator. The same treatment produces high levels of CPDs. In addition, DNA glycosylases, which recognize oxidized and ring-opened bases, did not produce significant cleavage of sunlight-irradiated DNA. From these data, we conclude that cyclobutane pyrimidine dimers are at least 20 to 40 times more frequent than any other DNA photoproduct when DNA or cells are irradiated with simulated sunlight.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alkalies / metabolism
  • DNA Damage / genetics
  • DNA Damage / radiation effects*
  • DNA Mutational Analysis
  • Deoxyribonuclease (Pyrimidine Dimer)
  • Dose-Response Relationship, Radiation
  • Endodeoxyribonucleases / metabolism
  • Fibroblasts / metabolism
  • Fibroblasts / radiation effects
  • Genes, p53 / genetics
  • Hot Temperature
  • Humans
  • Mutagenesis / genetics
  • Mutagenesis / radiation effects
  • Neurospora crassa
  • Oligodeoxyribonucleotides / chemistry
  • Oligodeoxyribonucleotides / genetics
  • Oligodeoxyribonucleotides / metabolism
  • Oligodeoxyribonucleotides / radiation effects
  • Piperidines / metabolism
  • Plasmids / chemistry
  • Plasmids / genetics
  • Plasmids / metabolism
  • Plasmids / radiation effects
  • Pyrimidine Dimers / chemistry
  • Pyrimidine Dimers / genetics
  • Pyrimidine Dimers / metabolism
  • Pyrimidine Dimers / radiation effects*
  • Reproducibility of Results
  • Time Factors
  • Ultraviolet Rays / adverse effects*


  • Alkalies
  • Oligodeoxyribonucleotides
  • Piperidines
  • Pyrimidine Dimers
  • piperidine
  • Endodeoxyribonucleases
  • Deoxyribonuclease (Pyrimidine Dimer)