It has previously been shown that the levels of poly(ADP-ribose)polymerase and polymers of ADP-ribose that co-purify with the nuclear matrix in regenerating liver fluctuate with the levels of in vivo DNA replication [(1988) FEBS Lett. 236, 362-366]. We have now electrophoretically identified lamins A and C, and poly(ADP-ribose)polymerase as the main protein targets for poly(ADP-ribosyl)ation in isolated nuclear matrices from adult rat liver. The identification of these protein acceptors was facilitated by the utilization of 32P-radiolabeled 3'-deoxyNAD as a substrate for nuclear matrix extracts in the presence of exogenously added DNA-dependent poly(ADP-ribose)polymerase from calf thymus. The extent of protein modification was time- and substrate concentration-dependent. These results are consistent with the hypothesis that the poly(ADP-ribose) modification of the lamins A and C and poly(ADP-ribose)polymerase are important to modulate chromatin-nuclear matrix interactions in rat liver.
