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Poly(ADP-ribose): spectator or participant in excision repair of DNA damage
Abstract:
Inhibition of poly(ADP-ribose) synthesis by 3-aminobenzamide in various human and hamster cell types influenced the responses to DNA damage from methyl methanesulfonate (MMS), but not from UV light. Excision of the major alkylation products and pyrimidine dimers was unaffected by 3-aminobenzamide. After exposure of cells to methyl methanesulfonate, 3-aminobenzamide increased the strand break frequency in all cell types studied, but stimulated repair replication only in lymphoid and HeLa cells, suggesting these are independent effects. 3-Aminobenzamide also inhibited the pathway for de novo synthesis of DNA purines, suggesting that some of its effects, particularly on repair replication, may be due to disturbance of precursor pathways. 3-Aminobenzamide stimulated sister chromatid exchange formation and mutagenesis but inhibited transformation, suggesting that some of these endpoints involve ADP-ribosylation by ways other than repair. Poly(ADP-ribose) synthesis appears to regulate the ligation stage of repair of alkylation damage by modulating a dynamic balance between incision and ligation, so as to minimize the frequency of DNA breaks.
Insights
3-aminobenzamide inhibits poly(ADP-ribose) synthesis, impacting DNA repair and cell responses to methyl methanesulfonate (MMS) damage. This suggests poly(ADP-ribose) synthesis regulates DNA repair ligation and other cellular processes.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Poly(ADP-ribose) polymerase (PARP) is involved in DNA repair.
- 3-aminobenzamide is a known inhibitor of PARP.
Purpose of the Study:
- To investigate the effects of 3-aminobenzamide on DNA damage responses in various cell types.
- To elucidate the role of poly(ADP-ribose) synthesis in DNA repair and other cellular processes.
Main Methods:
- Exposure of human and hamster cell lines to methyl methanesulfonate (MMS) and UV light.
- Treatment with 3-aminobenzamide to inhibit poly(ADP-ribose) synthesis.
- Assays for DNA strand breaks, repair replication, purine synthesis, sister chromatid exchange, mutagenesis, and transformation.
Main Results:
- 3-aminobenzamide inhibited poly(ADP-ribose) synthesis, affecting responses to MMS but not UV damage.
- Increased DNA strand breaks were observed after MMS exposure in the presence of 3-aminobenzamide.
- Stimulation of repair replication was cell-type specific, and purine synthesis was inhibited.
- 3-aminobenzamide stimulated sister chromatid exchange and mutagenesis but inhibited transformation.
Conclusions:
- Poly(ADP-ribose) synthesis plays a regulatory role in the ligation step of DNA alkylation repair.
- The effects of 3-aminobenzamide extend beyond DNA repair, influencing other cellular pathways.
- Poly(ADP-ribose) synthesis modulates the balance between DNA incision and ligation to minimize strand breaks.