Isolation and partial characterization of the ADP-ribosylated nuclear proteins from Ehrlich ascites tumor cells

The (ADP-ribose)_n protein conjugates formed by incubation of Ehrlich ascites tumor cell nuclei with 1 mM (³H)NAD were isolated by chromatography on boronate cellulose columns with a yield of >85%. Possible contamination by glycoproteins was excluded by rechromatography after specific release of the (ADP-ribose)_n residues from their acceptors. Dodecyl sulfate gel electrophoresis revealed numerous protein bands which coincided with the (³H)ADP-ribose bands obtained by fluorography of the gels. 40% of the acceptor proteins were identified as the nucleosomal core histones. Most of these histones, however, appeared in the non-histone fraction because of extensive modification by poly(ADP-ribose). Drastic changes in properties were also seen in the true non-histone proteins which comprised 60% of the total conjugated protein. Besides several prominent acceptor proteins (M_r = 12,000; 31,000; 125,000) numerous proteins were detected indicating a considerable heterogeneity of non-histone acceptors.