Biological consequences of DNA damage introduced in bacteriophage PM2 DNA by hydrogen peroxide-mediated free radical reactions

Johan J.P. Gille*, Natasja M. Wientjes, M. Vincent M. Lafleur, Hans Joenje, Jan Retèl

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


In order to study the biological consequences of DNA damage induced by H2O2-mediated free radical reactions, DNA from bacteriophage PM2 was exposed to H2O2, Fe3+-citrate and ascorbate either alone or in combination. Induction of DNA lesions was determined as well as the biological activity of the phage DNA. Exposure to H2O2 alone resulted in max. 0.2 single-strand breaks per molecule; in the presence of Fe3+-citrate, the yield was ~4-fold higher. Under both conditions no double-strand breaks could be detected and the biological activity was not diminished. This indicates that low levels of single-strand breaks as generated by H2O2/Fe3+-citrate do not inactivate PM2 DNA. Exposure to ascorbate in the presence Fe3+-citrate resulted in extensive induction of single-strand breaks. However, at ascorbate concentration where ~3 single-strand breaks per molecule were induced, again no double-strand breaks could be detected and the biological activity of the DNA was not diminished. At 5 mM ascorbate, single-strand breaks were above the detection limit. Under these conditions, 0.02 double-strand breaks were induced and the biological activity was reduced to 50%. The contribution of double-strand breaks to biological inactivation was calculated to be ~3%. When PM2 DNA was exposed to H2O2 in the presence of ascorbate/Fe3+-citrate, a typical biphasic dose-effect relationship was observed both for the induction of double-strand breaks and biological inactivation, suggesting that one or more reactive species sensitive to H2O2 play a critical role. The .OH scavenger t-butanol appeared to be relatively inefficient in protecting PM2 DNA, which may indicate that other reactive species than .OH are involved. Our data suggest that other reactive species than .OH, such as the ferryl ion, are involved in H2O2-mediated DNA damage induction and biological inactivation.

Original languageEnglish
Pages (from-to)5-11
Number of pages7
Issue number1
Publication statusPublished - Jan 1996

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