PARP-1 ensures regulation of replication fork progression by homologous recombination on damaged DNA

Abstract

Poly-ADP ribose polymerase 1 (PARP-1) is activated by DNA damage and has been implicated in the repair of single-strand breaks (SSBs). Involvement of PARP-1 in other DNA damage responses remains controversial. In this study, we show that PARP-1 is required for replication fork slowing on damaged DNA. Fork progression in PARP-1−/− DT40 cells is not slowed down even in the presence of DNA damage induced by the topoisomerase I inhibitor camptothecin (CPT). Mammalian cells treated with a PARP inhibitor or PARP-1–specific small interfering RNAs show similar results. The expression of human PARP-1 restores fork slowing in PARP-1−/− DT40 cells. PARP-1 affects SSB repair, homologous recombination (HR), and nonhomologous end joining; therefore, we analyzed the effect of CPT on DT40 clones deficient in these pathways. We find that fork slowing is correlated with the proficiency of HR-mediated repair. Our data support the presence of a novel checkpoint pathway in which the initiation of HR but not DNA damage delays the fork progression.

PARP1 is activated at telomeres upon G4 stabilization: possible target for telomere-based therapy

“…Telomere uncapping was triggered in BJ-HELT cells by reducing the expression of the telomeric proteins TRF2 and POT1 and by treating the cells with the selective G4 ligand RHPS4 (Salvati et al, 2007, Supplementary Figure 1). Cells were also exposed to camptothecin (CPT), a specific TOPO1 inhibitor causing DNA damage, including at the telomere level, by interfering with telomere replication (Sugimura et al, 2008), and to ionizing radiation generating non-specific DNA damage measured by gH2AX foci formation co-localizing with TRF1 ( Supplementary Figure 1). In agreement with previous studies (Lindahl et al, 1995), the poly-ADP ribosylation level had greatly increased in cells exposed to CPT and ionizing radiation (Figures 1a and b).…”

“…The fact that both RHPS4 and CPT interfere PARP inhibition increases the efficacy of telomere-based therapy E Salvati et al with DNA replication, together with the known PARP activation by stalled replication forks, suggest that PARP1 activation is caused by telomere replication defects (Sugimura et al, 2008;Rizzo et al, 2009).…”

Common fragile sites in colon cancer cell lines: Role of mismatch repair, RAD51 and poly(ADP-ribose) polymerase-1

“…PARP-1 has also been involved in regulation of the repair of DSBs by NHEJ [22]. Moreover, PARP-1 is required for slowing replication fork progression when replication fork collapse as a result of treatment with DSBs inducing agents [23]. The slowing of replication fork progression depends on the recruitment of HR pathway to the damage sites favoured by the ability of PARP-1 to suppress the inhibitory effect of NHEJ on HR [56].…”

“…Moreover, since poly(ADP-ribose) polymerase (PARP)-1 is involved in NHEJ-mediated repair of DSBs and ensures regulation of replication fork progression by HR on damaged DNA [21][22][23], we analyzed also the sensitivity to APC of colon cancer cell lines stably silenced for PARP-1 expression.…”

BRCA1, PARP, and 53BP1: conditional synthetic lethality and synthetic viability

“…PARP1/2 binds to and is activated by stalled replication forks during S-phase and PARP1/2 activity is required for the efficient HR-mediated restart of stalled replication forks (Yang et al, 2004;Sugimura et al, 2008). Depletion of PARP1 or PARP2 results in reduced recruitment of MRE11, RPA, and RAD51 to hydroxyureainduced collapsed replication forks, and reduces hydroxyureainduced recombination and fork restart (Yang et al, 2004).…”