Human proliferating cell nuclear antigen, poly(ADP-ribose) polymerase-1, and p21waf1/cip1. A dynamic exchange of partners

J Biol Chem. 2003 Oct 10;278(41):39265-8. doi: 10.1074/jbc.C300098200. Epub 2003 Aug 19.


We addressed the analysis of the physical and functional association of proliferating cell nuclear antigen (PCNA), a protein involved in many DNA transactions, with poly(ADP-ribose) polymerase (PARP-1), an enzyme that plays a crucial role in DNA repair and interacts with many DNA replication/repair factors. We demonstrated that PARP-1 and PCNA co-immunoprecipitated both from the soluble and the DNA-bound fraction isolated from S-phase-synchronized HeLa cells. Immunoprecipitation experiments with purified proteins further confirmed a physical association between PARP-1 and PCNA. To investigate the effect of this association on PARP-1 activity, an assay based on the incorporation of radioactive NAD was performed. Conversely, the effect of PARP-1 on PCNA-dependent DNA synthesis was assessed by a DNA polymerase delta assay. A marked inhibition of both reactions was found. Unexpectedly, PARP-1 activity also decreased in the presence of p21waf1/cip1. By pull-down experiments, we provided the first evidence for an association between PARP-1 and p21, which involves the C-terminal part of p21 protein. This association was further demonstrated to occur also in vivo in MNNG (N-methyl-N'-nitro-N-nitrosoguanidine)-treated human fibroblasts. These observations suggest that PARP-1 and p21 could cooperate in regulating the functions of PCNA during DNA replication/repair.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cells, Cultured
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins / metabolism*
  • DNA Polymerase III / antagonists & inhibitors
  • DNA Repair
  • DNA Replication
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism
  • HeLa Cells
  • Humans
  • Methylnitronitrosoguanidine / pharmacology
  • Poly(ADP-ribose) Polymerase Inhibitors
  • Poly(ADP-ribose) Polymerases / isolation & purification
  • Poly(ADP-ribose) Polymerases / metabolism*
  • Precipitin Tests
  • Proliferating Cell Nuclear Antigen / isolation & purification
  • Proliferating Cell Nuclear Antigen / metabolism*
  • Recombinant Proteins / metabolism


  • CDKN1A protein, human
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins
  • Poly(ADP-ribose) Polymerase Inhibitors
  • Proliferating Cell Nuclear Antigen
  • Recombinant Proteins
  • Methylnitronitrosoguanidine
  • Poly(ADP-ribose) Polymerases
  • DNA Polymerase III