Poly(ADP-RIBOSE) polymerase-1 (Parp-1) antagonizes topoisomerase I-dependent recombination stimulation by P53

摘要

PARP-1 interacts with and poiy(ADP-ribosyf)ates p53 and topoisomerase E, which both participate in DMA recombination. Previously, we showed that PARP-1 downregulates homology-directed double-strand break (DS8) repair. We also discovered that, despitethe well-established role of p53 as a global suppressor of error-prone recombination, p53 enhances homologous recombination (HR) at trie RAR alpha breakpoint cluster region (ber) comprising topoisomerase I recognition sites. Using an SV40-based assay andisogenic ceil lines differing in the p53 and PARP-1 status we demonstrate that PARP-1 counteracts HR enhancement by p53, although DNA replication was largely unaffected. When the same DNA element was integrated in an episomal recombination plasmid, bothp53 and PARP-1 exerted anti-reeomblnogenic rather than stimulatory activities. Strikingly, with DNA substrates integrated into cellular chromosomes, enhancement of HR by p53 and antagonistic PARP-1 action was seen, very similar to the HR of viral minichromosomes. siRNA-mediated knockdown revealed the essential role of topoisomerase I in this regulatory mechanism. However, after I-Scel-meganucleasemediated cleavage of the chromosomslly integrated substrate, no topoisomerase I-dependent effects by p53 and PARP-1 were observed. Our data further indicate that PARP-1, probably through topoisomerase I interactions rather than poly(ADP-ribosyl)ation, prevents p53 from stimulating spontaneous HR on chromosomes via topoisomerase I activity.