Repair of single-strand DNA interruptions by redundant pathways and its implication in cellular sensitivity to DNA-damaging agents.
Single-strand DNA interruptions (SSIs) are produced during the process of base excision repair (BER). Through biochemical studies, two SSI repair subpathways have been identified: a pathway mediated by DNA polymerase beta (Pol beta) and DNA ligase III (Lig III), and a pathway mediated by DNA polymerase delta/epsilon (Pol delta/epsilon) and DNA ligase I (Lig I). In addition, the existence of another pathway, mediated by Pol beta and DNA Lig I, has been suggested. Although each pathway may play a unique role in cellular DNA damage response, the functional implications of SSI repair by these three pathways are not clearly understood. To obtain a better understanding of the functional relevance of SSI repair by these pathways, we investigated the involvement of each pathway by monitoring the utilization of DNA ligases in cell-free extracts. Our results suggest that the majority of SSIs produced during the repair of alkylated DNA bases are repaired by the pathway mediated by Pol beta and either Lig I or Lig III, although some SSIs are repaired by Pol delta/epsilon and Lig I. At a cellular level, we found that Lig III over-expression increased the resistance of cells to DNA-damaging agents, while Lig I over-expression had little effect. Thus, repair pathways mediated by Lig III may have a role in the regulation of cellular sensitivity to DNA-damaging agents.
Ho
Erick L Y
EL
Laboratory of DNA Repair, Health and Environment Unit, Laval University Medical Center, CHUQ, Faculty of Medicine, Laval University, 2705 Boulevard Laurier, Ste-Foy, Quebec G1V 4G2, Canada.
Satoh
Masahiko S
MS
D000249:Adenosine Monophosphate / Q000378:metabolism; D000478:Alkylation / Q000187:drug effects; D016590:Aphidicolin / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002474:Cell-Free System; D004249:DNA Damage / Q000187:drug effects; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism*; D004257:DNA Polymerase II / Q000378:metabolism; D004258:DNA Polymerase III / Q000378:metabolism; D019951:DNA Polymerase beta / Q000378:metabolism*; D004260:DNA Repair; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology; D008863:Microspheres; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D000075223:Poly-ADP-Ribose Binding Proteins; D029867:Xenopus Proteins
D004277:DNA, Single-Stranded; C000607892:LIG1 protein, human; D000075223:Poly-ADP-Ribose Binding Proteins; D029867:Xenopus Proteins; D008769:Methylnitronitrosoguanidine; D016590:Aphidicolin; D000249:Adenosine Monophosphate; D004257:DNA Polymerase II; D004258:DNA Polymerase III; D019951:DNA Polymerase beta; D011088:DNA Ligases; D000072481:DNA Ligase ATP; C000618816:DNA ligase III alpha protein, Xenopus; C000618817:LIG3 protein, human