[Poly(ADP-ribosylation) of nuclear proteins in rat thymocytes]

Specific antibodies to poly(ADP-ribose) were obtained and characterized. Using these antibodies, the tissue specificity of poly(ADP-ribose) modified nuclear proteins from rat thymocytes and hepatocytes was studied. The differences in the levels of poly(ADP-ribosylation) of nuclear proteins from both tissues were found to be quantitative rather than qualitative. Analysis of intranuclear distribution of poly(ADP-ribose) acceptor proteins revealed that the bulk of them is localized in the nuclear sap and matrix. A comparison of spectral properties of poly(ADP-ribosylated) proteins, using specific antibodies and label incorporation from [14C]NAD showed the existence of two protein groups. Some of those were modified in a great degree but exchange poly(ADP-ribose) at a slow rate, whereas others (e.g., histones and HMG proteins) modified in a small degree exchanged poly(ADP-ribose) at a much higher rate. The results obtained by different methods are discussed.