The PCNA-associated protein PARI negatively regulates homologous recombination via the inhibition of DNA repair synthesis

Nucleic Acids Res. 2016 Apr 20;44(7):3176-89. doi: 10.1093/nar/gkw024. Epub 2016 Jan 20.


Successful and accurate completion of the replication of damage-containing DNA requires mainly recombination and RAD18-dependent DNA damage tolerance pathways. RAD18 governs at least two distinct mechanisms: translesion synthesis (TLS) and template switching (TS)-dependent pathways. Whereas TS is mainly error-free, TLS can work in an error-prone manner and, as such, the regulation of these pathways requires tight control to prevent DNA errors and potentially oncogenic transformation and tumorigenesis. In humans, the PCNA-associated recombination inhibitor (PARI) protein has recently been shown to inhibit homologous recombination (HR) events. Here, we describe a biochemical mechanism in which PARI functions as an HR regulator after replication fork stalling and during double-strand break repair. In our reconstituted biochemical system, we show that PARI inhibits DNA repair synthesis during recombination events in a PCNA interaction-dependent way but independently of its UvrD-like helicase domain. In accordance, we demonstrate that PARI inhibits HR in vivo, and its knockdown suppresses the UV sensitivity of RAD18-depleted cells. Our data reveal a novel human regulatory mechanism that limits the extent of HR and represents a new potential target for anticancer therapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • DNA / biosynthesis
  • DNA Polymerase III / antagonists & inhibitors
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / metabolism*
  • DNA-Binding Proteins / physiology
  • HEK293 Cells
  • Humans
  • Recombinational DNA Repair*
  • Ubiquitin-Protein Ligases / physiology
  • Ultraviolet Rays


  • DNA-Binding Proteins
  • PARPBP protein, human
  • RAD18 protein, human
  • DNA
  • Ubiquitin-Protein Ligases
  • DNA Polymerase III