title: Poly (ADP-ribose) polymerase (PARP) is essential for sulfur mustard-induced DNA damage repair, but has no role in DNA ligase activation.
abstract: Concurrent activation of poly (ADP-ribose) polymerase (PARP) and DNA ligase was observed in cultured human epidermal keratinocytes (HEK) exposed to the DNA alkylating compound sulfur mustard (SM), suggesting that DNA ligase activation could be due to its modification by PARP. Using HEK, intracellular 3H-labeled NAD+ (3H-adenine) was metabolically generated and then these cells were exposed to SM (1 mM). DNA ligase I isolated from these cells was not 3H-labeled, indicating that DNA ligase I is not a substrate for (ADP-ribosyl)ation by PARP. In HEK, when PARP was inhibited by 3-amino benzamide (3-AB, 2 mM), SM-activated DNA ligase had a half-life that was four-fold higher than that observed in the absence of 3-AB. These results suggest that DNA repair requires PARP, and that DNA ligase remains activated until DNA damage repair is complete. The results show that in SM-exposed HEK, DNA ligase I is activated by phosphorylation catalysed by DNA-dependent protein kinase (DNA-PK). Therefore, the role of PARP in DNA repair is other than that of DNA ligase I activation. By using the DNA ligase I phosphorylation assay and decreasing PARP chemically as well as by PARP anti-sense mRNA expression in the cells, it was confirmed that PARP does not modify DNA ligase I. In conclusion, it is proposed that PARP is essential for efficient DNA repair; however, PARP participates in DNA repair by altering the chromosomal structure to make the DNA damage site(s) accessible to the repair enzymes.
authors.affiliation: Department of Chemistry, Lincoln University, Lincoln University PA-19352-0999, USA. radharaman.ray@us.army.mil
authors.forename: K Ramachandra
authors.initials: KR
authors.lastname: Bhat
authors.forename: Betty J
authors.initials: BJ
authors.lastname: Benton
authors.forename: Radharaman
authors.initials: R
authors.lastname: Ray
mesh_terms: D017209:Apoptosis; D001549:Benzamides / Q000494:pharmacology; D002478:Cells, Cultured; D002619:Chemical Warfare Agents / Q000633:toxicity*; D004249:DNA Damage; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism*; D004260:DNA Repair; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000078404:Epidermal Cells; D004817:Epidermis / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000201:enzymology; D009151:Mustard Gas / Q000633:toxicity*; D010766:Phosphorylation; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism*; D016372:RNA, Antisense / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D001549:Benzamides; D002619:Chemical Warfare Agents; D004791:Enzyme Inhibitors; C000607892:LIG1 protein, human; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D016372:RNA, Antisense; C025160:3-aminobenzamide; D011065:Poly(ADP-ribose) Polymerases; D011088:DNA Ligases; D000072481:DNA Ligase ATP; D009151:Mustard Gas