FUNCTIONAL ASSOCIATION OF POLY(ADP-RIBOSE) POLYMERASE WITH DNA-POLYMERASE ALPHA-PRIMASE COMPLEX - A LINK BETWEEN DNA STRAND BREAK DETECTIONAND DNA-REPLICATION

Poly(ADP-ribose) polymerase (PARP) is an element of the DNA damage sur veillance network evolved by eukaryotic cells to cope with numerous en vironmental and endogenous genotoxic agents. PARP has been found to be involved in vivo in both cell proliferation and base excision repair of DNA, In this study the interaction between PARP and the DNA polymer ase alpha-primase tetramer has been examined. We provide evidence that in proliferating cells: (i) PARP is physically associated with the ca talytic subunit of the DNA polymerase alpha-primase tetramer, an assoc iation confirmed by confocal microscopy, demonstrating that both enzym es are co-localized at the nuclear periphery of HeLa cells; (ii) this interaction requires the integrity of the second zinc finger of PARR a nd is maximal during the S and G2/M phases of the cell cycle; (iii) PA RP-deficient cells derived from PARP knock-out mice exhibited reduced DNA polymerase activity, compared with the parental cells, a reduction accentuated following exposure to sublethal doses of methylmethanesul fonate. Altogether, the present results strongly suggest that PARR par ticipates in a DNA damage survey mechanism implying its nick-sensor fu nction as part of the control of replication fork progression when bre aks are present in the template.