Poly (ADP-Ribose) Polymerase is Involved in the Repair of DNA Damage Due to Sulfur Mustard by a Mechanism Other Than DNA Ligase I Activation
Abstract
Poly (ADP-ribose) polymerase (PARP) modulates several cellular functional proteins by a mechanism in which the proteins are poly-ADP-ribosylated by transferring the ADP-ribose moieties from the enzyme substrate NAD+ to the proteins. PARP is activated following damage to cellular DNA by alkylating agents including sulfur mustard (SM). We observed concurrent activation of PARP and DNA ligase in SM-exposed human epidermal keratinocytes (HEK). Previous reports from other laboratories suggested that DNA ligase activation could be due to its modification by PARP. In humans, there are three distinct DNA ligases, I, II and IV of which DNA ligase I participates in DNA replication and repair. By metabolically labeling HEK using 3H-adenosine (adenosine 2,8-3H) to generate intracellularly radiolabeled NAD+ (3H-adenine) and then exposing the cells containing 3H-NAD+ to 1 mM SM, we found that isolated DNA ligase I was not 3H-labeled. This result indicates that DNA ligase I is not a substrate for ADP-ribosylation by PARP. Interestingly, our results show an effect of PARP inhibition on the decay of activated DNA ligase following exposure of HEK to SM. In the presence of 2 mM 3-amino benzamide (3-AB), a PARP inhibitor, the activated DNA ligase has a half-life that is four-fold higher than that observed in the absence of 3-AB. SM-induced DNA damage repair is dependent on DNA ligase I activation, which we have found to occur via phosphorylation catalyzed by DNA-dependent protein kinase (DNA-PK). The longer half-life of DNA ligase I observed when PARP is inhibited suggests that DNA repair requires PARP, and that DNA ligase I remains activated until DNA damage repair is complete. Therefore, PARP is involved in DNA repair mechanisms other than that of DNA ligase I activation. PARP inhibitors have been suggested as prospective SM antidotes.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 16, 2004
- Accession Number
- ADA449692
Entities
People
- Betty J. Benton
- K. Ramachandra Bhat
- Radharaman Ray
Organizations
- University of Lincoln