Purification of ADP-ribosylated nuclear proteins by covalent chromatography on dihydroxyboryl polyacrylamide beads and their characterization.

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RESUMO

Nuclear proteins modified by mono or poly ADP-ribosylation were selectively isolated and purified by covalent chromatography on a dihydroxyboryl polyacrylamide bead column that specifically interacts with cis-diol-containing compounds. From rat liver nuclei that had been incubated with NAD+, histones and some nonhistone proteins were extracted with 0.25 M HCl. Approximately 60% of the ADP-ribose incorporated into 20% trichloroacetic acid-precipitable material was recovered in this extract. The ADP-ribosylated material was then isolated from the extract by covalent chromatography on a borate gel column and further purified by carboxymethylcellulose column chromatography. As judged by electrophoretic mobilities in various gel systems and by amino acid compositions, approximately 50% of the ADP-ribose recovered in the carboxymethylcellulose fractions was associated with several nonhistone proteins with molecular weights of 2-6 x 10(4), while 35% aand 15% were associated with histones H2B and H1, respectively. Since the average chain length of the polymer bound to any of these proteins was less than two ADP-ribos-l units, the percentage distribution reflects the number of ADP-ribosylated sites rather than the chain length.

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