Poly(ADP-ribose) polymerase (PARP-1) is not involved in DNA double-strand break recovery.
BACKGROUND
The cytotoxicity and the rejoining of DNA double-strand breaks induced by gamma-rays, H2O2 and neocarzinostatin, were investigated in normal and PARP-1 knockout mouse 3T3 fibroblasts to determine the role of poly(ADP-ribose) polymerase (PARP-1) in DNA double-strand break repair.


RESULTS
PARP-1-/- were considerably more sensitive than PARP-1+/+ 3T3s to induced cell kill by gamma-rays and H2O2. However, the two cell lines did not show any significant difference in the susceptibility to neocarzinostatin below 1.5 nM drug. Restoration of PARP-1 expression in PARP-1-/- 3T3s by retroviral transfection of the full PARP-1 cDNA did not induce any change in neocarzinostatin response. Moreover the incidence and the rejoining kinetics of neocarzinostatin-induced DNA double-strand breaks were identical in PARP-1+/+ and PARP-1-/- 3T3s. Poly(ADP-ribose) synthesis following gamma-rays and H2O2 was observed in PARP-1-proficient cells only. In contrast neocarzinostatin, even at supra-lethal concentration, was unable to initiate PARP-1 activation yet it induced H2AX histone phosphorylation in both PARP1+/+ and PARP-1-/- 3T3s as efficiently as gamma-rays and H2O2.


CONCLUSIONS
The results show that PARP-1 is not a major determinant of DNA double-strand break recovery with either strand break rejoining or cell survival as an endpoint. Even though both PARP-1 and ATM activation are major determinants of the cell response to gamma-rays and H2O2, data suggest that PARP-1-dependent poly(ADP-ribose) synthesis and ATM-dependent H2AX phosphorylation, are not inter-related in the repair pathway of neocarzinostatin-induced DNA double-strand breaks.
Noël
Georges
G
Unité 350 INSERM, Institut Curie-Recherche, Bâts, 110-112, Centre Universitaire, 91405 Orsay Cedex, France. noel@ipno.in2p3.fr
Giocanti
Nicole
N
Fernet
Marie
M
Mégnin-Chanet
Frédérique
F
Favaudon
Vincent
V
D000818:Animals; D004249:DNA Damage; D004260:DNA Repair; D005455:Fluorescent Antibody Technique; D005720:Gamma Rays; D006861:Hydrogen Peroxide / Q000633:toxicity; D051379:Mice; D018345:Mice, Knockout; D041681:NIH 3T3 Cells; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000502:physiology*; D009353:Zinostatin / Q000633:toxicity
D009353:Zinostatin; D006861:Hydrogen Peroxide; D011065:Poly(ADP-ribose) Polymerases