Increased resistance of the Chinese hamster mutant irs1 cells to monofunctional alkylating agents by transfection of the E. coli or mammalian N3-methyladenine-DNA-glycosylase genes

Mutat Res. 1993 Mar;293(3):187-95. doi: 10.1016/0921-8777(93)90069-s.


Irs1 cells are mutants of the Chinese hamster cell line V79-4, and exhibit cross-sensitivity to various DNA-damaging agents, especially to the alkylating compounds methyl methanesulfonate and ethyl methanesulfonate. To test whether this sensitivity was due to the persistence of alkylated residues in DNA, we have transfected irs1 cells with the pMSG expression vector containing two coding sequences for enzymes of different origin, either the E. coli AlkA gene, coding for 3-methyladenine-DNA-glycosylase II, or rat APDG cDNA, encoding alkylpurine-DNA-glycosylase. The two coding sequences for the repair enzymes were ligated in the pMSG vector, under the control of the MMTV-LTR promoter, which is responsive to glucocorticoid regulation. The presence of the AlkA gene or of the APDG cDNA in the transfected cells was detected by Southern blot analysis and the transcription of these foreign sequences was checked by Northern hybridization of the cellular RNA. The transfected irs1 cells treated with [3H]dimethylsulfate removed the 3-methyladenine residues more efficiently from their DNA than the control cells. Irs1 cells harboring the AlkA or the APDG gene become about 2- and 3-fold more resistant to the toxic effect of methyl methanesulfonate, respectively. However, a 3-fold resistance to ethyl methanesulfonate was only observed in irs1 cells harboring the mammalian APDG cDNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / analogs & derivatives
  • Adenine / metabolism
  • Alkylating Agents / toxicity*
  • Animals
  • Cell Line
  • Cricetinae
  • DNA / drug effects
  • DNA / metabolism
  • DNA Glycosylases*
  • DNA Repair*
  • Dexamethasone / pharmacology
  • Drug Resistance / genetics
  • Escherichia coli / genetics
  • Ethyl Methanesulfonate / pharmacology
  • Methyl Methanesulfonate / pharmacology
  • N-Glycosyl Hydrolases / genetics*
  • Rats
  • Transfection*


  • Alkylating Agents
  • 3-methyladenine
  • Dexamethasone
  • DNA
  • Ethyl Methanesulfonate
  • Methyl Methanesulfonate
  • 3-methyladenine-DNA glycosylase
  • DNA Glycosylases
  • N-Glycosyl Hydrolases
  • Adenine