Digestion of damaged DNA by the T7 DNA polymerase-exonuclease

Biochem J. 1993 Jul 15;293 ( Pt 2)(Pt 2):451-3. doi: 10.1042/bj2930451.


We have investigated the 3'-5'-exonuclease activity of phage T7 DNA polymerase for its usefulness as an approach for the detection of lesions in DNA. Unlike the T4 DNA polymerase-exonuclease, which is commonly used to map the position and frequency of lesions in very small DNA fragments, T7 DNA polymerase-exonuclease is able to hydrolyse almost completely the large fragments from KpnI-restricted mammalian DNA. However, we found that the exonuclease was also able to hydrolyse DNA containing several kinds of lesions: cyclobutane pyrimidine dimers, thymine glycols, and mono-adducts of 4'-hydroxymethyl-4,5',8-trimethylpsoralen and 5'-methyl-isopsoralen. Modifications of the reaction conditions did not significantly alter the extent of hydrolysis. These properties distinguish the T7 DNA polymerase-exonuclease from the T4 DNA polymerase-exonuclease and make the T7 DNA polymerase-exonuclease unsuitable for detecting several types of lesions in DNA.

Publication types

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

MeSH terms

  • Animals
  • CHO Cells
  • Cricetinae
  • DNA / drug effects
  • DNA / metabolism*
  • DNA / radiation effects
  • DNA Damage*
  • DNA-Directed DNA Polymerase / metabolism*
  • Exodeoxyribonuclease V
  • Exodeoxyribonucleases / metabolism*
  • Ficusin / pharmacology
  • Hydrolysis
  • Ultraviolet Rays


  • DNA
  • bacteriophage T7 induced DNA polymerase
  • DNA-Directed DNA Polymerase
  • Exodeoxyribonucleases
  • Exodeoxyribonuclease V
  • Ficusin