Evidence that a burst of DNA depurination in SENCAR mouse skin induces error-prone repair and forms mutations in the H-ras gene

Oncogene. 2001 Nov 29;20(55):7945-53. doi: 10.1038/sj.onc.1204969.


Treatment of SENCAR mouse skin with dibenzo[a,l]pyrene results in abundant formation of abasic sites that undergo error-prone excision repair, forming oncogenic H-ras mutations in the early preneoplastic period. To examine whether the abundance of abasic sites causes repair infidelity, we treated SENCAR mouse skin with estradiol-3,4-quinone (E(2)-3,4-Q) and determined adduct levels 1 h after treatment, as well as mutation spectra in the H-ras gene between 6 h and 3 days after treatment. E(2)-3,4-Q formed predominantly (> or =99%) the rapidly-depurinating 4-hydroxy estradiol (4-OHE(2))-1-N3Ade adduct and the slower-depurinating 4-OHE(2)-1-N7Gua adduct. Between 6 h and 3 days, E(2)-3,4-Q induced abundant A to G mutations in H-ras DNA, frequently in the context of a 3'-G residue. Using a T.G-DNA glycosylase (TDG)-PCR assay, we determined that the early A to G mutations (6 and 12 h) were in the form of G.T heteroduplexes, suggesting misrepair at A-specific depurination sites. Since G-specific mutations were infrequent in the spectra, it appears that the slow rate of depurination of the N7Gua adducts during active repair may not generate a threshold level of G-specific abasic sites to affect repair fidelity. These results also suggest that E(2)-3,4-Q, a suspected endogenous carcinogen, is a genotoxic compound and could cause mutations.

Publication types

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

MeSH terms

  • Animals
  • Artifacts
  • Base Sequence
  • DNA Adducts / chemistry
  • DNA Adducts / drug effects
  • DNA Adducts / genetics*
  • DNA Damage / drug effects
  • DNA Damage / genetics*
  • DNA Mutational Analysis
  • DNA Repair / drug effects
  • DNA Repair / genetics*
  • Estradiol / analogs & derivatives*
  • Estradiol / chemistry
  • Estradiol / pharmacology
  • Female
  • Genes, ras / genetics*
  • Mice
  • Mice, Inbred SENCAR
  • Mutagenesis / genetics*
  • Mutagens / chemistry
  • Mutagens / pharmacology
  • Nucleic Acid Heteroduplexes / drug effects
  • Nucleic Acid Heteroduplexes / genetics
  • Point Mutation / genetics
  • Polymerase Chain Reaction
  • Skin / drug effects
  • Skin / metabolism*


  • DNA Adducts
  • Mutagens
  • Nucleic Acid Heteroduplexes
  • estradiol-2,3-O-quinone
  • Estradiol