Poly-ADP-ribosyltransferase that mediates poly-ADP-ribosylation of proteins and plays a key role in DNA repair (PubMed:17827147). Mediates glutamate, aspartate or serine ADP-ribosylation of proteins: the ADP-D-ribosyl group of NAD(+) is transferred to the acceptor carboxyl group of target residues and further ADP-ribosyl groups are transferred to the 2'-position of the terminal adenosine moiety, building up a polymer with an average chain length of 20-30 units (By similarity). Mainly mediates glutamate and aspartate ADP-ribosylation of target proteins in absence of CG1218/HPF1 (By similarity). Following interaction with CG1218/HPF1, catalyzes serine ADP-ribosylation of target proteins; CG1218/HPF1 conferring serine specificity by completing the Parp active site (By similarity). Plays a fundamental role in organizing chromatin on a global scale (PubMed:12183365). Autoregulates Parp transcription by influencing the chromatin structure of its heterochromatic environment (PubMed:12183365). NAD(+) + (ADP-D-ribosyl)n-acceptor = nicotinamide + (ADP-D-ribosyl)n+1-acceptor + H(+). L-seryl-[protein] + NAD(+) = H(+) + nicotinamide + O-(ADP-D-ribosyl)-L-seryl-[protein] L-aspartyl-[protein] + NAD(+) = 4-O-(ADP-D-ribosyl)-L-aspartyl-[protein] + nicotinamide L-glutamyl-[protein] + NAD(+) = 5-O-(ADP-D-ribosyl)-L-glutamyl-[protein] + nicotinamide Highly enriched in nucleoli, heterochromatic chromosomal regions, and diverse euchromatic sites in the cells of most embryonic and adult tissues (PubMed:12183365). Localizes in chromatin and nucleoplasm (PubMed:17827147). Expressed in adult female oocytes, anal plates of stage 12 embryos and in cells around the central nervous system in later embryos. Expressed both maternally and zygotically in embryos, pupae and adults. Expression is highest in embryos.