PARP inhibition versus PARP-1 silencing: different outcomes in terms of single-strand break repair and radiation susceptibility

Nucleic Acids Res. 2008 Aug;36(13):4454-64. doi: 10.1093/nar/gkn403. Epub 2008 Jul 4.

Abstract

The consequences of PARP-1 disruption or inhibition on DNA single-strand break repair (SSBR) and radio-induced lethality were determined in synchronized, isogenic HeLa cells stably silenced or not for poly(ADP-ribose) polymerase-1 (PARP-1) (PARP-1(KD)) or XRCC1 (XRCC1(KD)). PARP-1 inhibition prevented XRCC1-YFP recruitment at sites of 405 nm laser micro irradiation, slowed SSBR 10-fold and triggered the accumulation of large persistent foci of GFP-PARP-1 and GFP-PCNA at photo damaged sites. These aggregates are presumed to hinder the recruitment of other effectors of the base excision repair (BER) pathway. PARP-1 silencing also prevented XRCC1-YFP recruitment but did not lengthen the lifetime of GFP-PCNA foci. Moreover, PARP-1(KD) and XRCC1(KD) cells in S phase completed SSBR as rapidly as controls, while SSBR was delayed in G1. Taken together, the data demonstrate that a PARP-1- and XRCC1-independent SSBR pathway operates when the short patch repair branch of the BER is deficient. Long patch repair is the likely mechanism, as GFP-PCNA recruitment at photo-damaged sites was normal in PARP-1(KD) cells. PARP-1 silencing elicited hyper-radiosensitivity, while radiosensitization by a PARP inhibitor reportedly occurs only in those cells treated in S phase. PARP-1 inhibition and deletion thus have different outcomes in terms of SSBR and radiosensitivity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 1-Naphthylamine / analogs & derivatives
  • 1-Naphthylamine / pharmacology
  • DNA / radiation effects
  • DNA Breaks, Single-Stranded*
  • DNA Repair* / drug effects
  • DNA-Binding Proteins / antagonists & inhibitors
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Enzyme Inhibitors / pharmacology
  • G1 Phase
  • Gamma Rays
  • HeLa Cells
  • Humans
  • Lasers
  • Naphthalimides / pharmacology
  • Poly (ADP-Ribose) Polymerase-1
  • Poly(ADP-ribose) Polymerase Inhibitors*
  • Poly(ADP-ribose) Polymerases / genetics
  • Poly(ADP-ribose) Polymerases / metabolism
  • Proliferating Cell Nuclear Antigen / metabolism
  • Quinolones / pharmacology
  • RNA Interference
  • Radiation Tolerance*
  • S Phase
  • X-ray Repair Cross Complementing Protein 1

Substances

  • DNA-Binding Proteins
  • Enzyme Inhibitors
  • Naphthalimides
  • Poly(ADP-ribose) Polymerase Inhibitors
  • Proliferating Cell Nuclear Antigen
  • Quinolones
  • X-ray Repair Cross Complementing Protein 1
  • XRCC1 protein, human
  • 4-amino-1,8-naphthalimide
  • DNA
  • 1-Naphthylamine
  • PARP1 protein, human
  • Poly (ADP-Ribose) Polymerase-1
  • Poly(ADP-ribose) Polymerases