Functional Interaction between Poly(ADP-Ribose) Polymerase 2 (PARP-2) and TRF2: PARP Activity Negatively Regulates TRF2

Abstract

The DNA damage-dependent poly(ADP-ribose) polymerase-2 (PARP-2) is, together with PARP-1, an active player of the base excision repair process, thus defining its key role in genome surveillance and protection. Telomeres are specialized DNA-protein structures that protect chromosome ends from being recognized and processed as DNA strand breaks. In mammals, telomere protection depends on the T₂AG₃ repeat binding protein TRF2, which has been shown to remodel telomeres into large duplex loops (t-loops). In this work we show that PARP-2 physically binds to TRF2 with high affinity. The association of both proteins requires the N-terminal domain of PARP-2 and the myb domain of TRF2. Both partners colocalize at promyelocytic leukemia bodies in immortalized telomerase-negative cells. In addition, our data show that PARP activity regulates the DNA binding activity of TRF2 via both a covalent heteromodification of the dimerization domain of TRF2 and a noncovalent binding of poly(ADP-ribose) to the myb domain of TRF2. PARP-2^−/− primary cells show normal telomere length as well as normal telomerase activity compared to wild-type cells but display a spontaneously increased frequency of chromosome and chromatid breaks and of ends lacking detectable T₂AG₃ repeats. Altogether, these results suggest a functional role of PARP-2 activity in the maintenance of telomere integrity.

We thank Titia de Lange (Rockefeller University) for anti-TRF2 antibodies.

This work was supported by the Association pour la Recherche Contre le Cancer, Ligue Nationale contre le Cancer et Comité Régional, Electricité de France, Commissariat à l'Energie Atomique, and Centre National de la Recherche Scientifique. I.J. is a predoctoral fellow of the Gulbenkian Foundation, Portugal. The M.B. laboratory is funded by The Swiss Bridge Cancer Research Award 2000, by the Josef Steiner Cancer Research Award 2003, by The Genome Special Action of the Ministry of Science and Technology of Spain (MCYT; GEN2001-4856-C13-08), by grant SAF2001-1869 from the MCYT, by grant 08.1/0054/01 from the CAM, by EU grants FIGH CT 1999-00009, FIGH CT 1999-00002, QLG1 1999-01341, and FIS5-2002-00078, and by the Department of Immunology and Oncology (DIO). The DIO is funded by the Spanish Council for Scientific Research and by Pharmacia Corporation.