Detection of poly(ADP-ribose) synthesis in Drosophila testes upon gamma-irradiation

Poly(ADP-ribose) polymerase (PARP) activity is widespread among eukaryotes. Upon DNA damage PARP binds to DNA strand breaks and transfers ADP-ribose r esidues from NAD(+) to acceptor proteins and to ADP-ribosyl protein adducts . This leads to branched polymers of protein-coupled paly(ADP-ribose) (pADP r). Because the germline of Drosophila has recently become important in the study of DNA double-strand break repair (DSBR) as opposed to somatic DSBR we tested whether the catalytic activity of PARP can be stimulated by gamma -irradiation during Drosophila spermatogenesis. Using antibodies against pA DPr we detected a significant increase in PARP activity in male germline ce lls during spermatogenesis upon gamma-irradiation. Different stages of sper matogenesis revealed different subnuclear localization patterns of pADPr, I n premeiotic and postmeiotic cells pADPr localized in a pattern overlapping with lamin and topoisomerase II at the nuclear rim. In primary spermatocyt es pADPr is associated with three loci corresponding to the chromosomes at the nuclear periphery.