Inhibition of poly(ADP-ribose) synthesis may affect DNA repair prior to ligation

Publisher Website
Google Scholar
Abstract
The effects of modification of poly(ADP-ribosyl)ation reactions have been examined in normal (F107) and ataxia telangiectasia (AT23) fibroblasts following damage by methyl methanesulphonate (MMS) and u.v. light. The technique of benzoylated DEAE (BD)-cellulose chromatography was utilized to estimate both the extent and nature of the damage to DNA induced by these agents and to examine the effects of an inhibitor of poly(ADP-ribose) synthetase, 3-aminobenzamide (3AB), on these parameters. Single strand breakage, determined by nucleoid sedimentation, and levels of poly ADP(ribose) synthesis were monitored. Increase in the proportion of DNA containing single-stranded regions, as measured by stepwise elution from BD-cellulose, was observed following MMS damage in both cell types. In the presence of 3AB, a further accumulation of DNA containing single-stranded regions occurred, with the effect being more prominent in AT23 fibroblasts. U.v. light damage did not induce the increased binding to BD-cellulose in normal cells, and the increase observed in AT23 cells was much less than that seen following alkylation damage. Examination of the nature of single-stranded damage by caffeine gradient elution from BD-cellulose following MMS treatment revealed discrete structural lesions, which were enhanced in the presence of 3AB. A similar effect was exerted by arabinofuranosyl cytosine. The behaviour of these intermediates, which could be associated with repair, was not in accord with the suggestion that 3AB inhibits only the ligation stage of the repair process. Our results suggest that specific intermediate stages in DNA repair are sensitive to 3AB, and it seems likely that these stages occur prior to ligation.
Keywords