In vitro ADP-ribosylation of nuclear proteins in mouse tissues. Identification of an unusual group of acceptors in testis nuclei.

1. Acceptor proteins for poly(ADP-ribose) have been identified in nuclei from mouse testis, liver, kidney and spleen. Purified nuclei were incubated in vitro with [14C]NAD, extracted sequentially with 5% HClO4 and 0.25 N-HCl and labelled proteins analysed on acetic acid/urea polyacrylamide gels pH 2.9. 2. Results show that: (a) in vitro there are significant differences between tissues in the extent of poly(ADP-ribosylation) of nuclear proteins; (b) in testis nuclei two tissue specific proteins are poly(ADP-ribosylated) to higher specific activity than histones; (c) there are significant differences between in vivo and in vitro studies on poly(ADP-ribosylation) of nuclear proteins in testis nuclei.