Polyoma virus minichromosomes: poly ADP-ribosylation of associated chromatin proteins.

The host nuclear enzyme poly(ADP-ribose) polymerase has been shown to be associated with the replicative intermediate and mature forms of polyoma virus minichromosomes. Minichromosome-associated histones H2A and H2B as well as several nonhistone proteins were poly ADP-ribosylated by endogenous poly(ADP-ribose) polymerase. In addition, minichromosome fractions catalyzed the formation in vitro of dimers of endogenous histone H1 linked by poly(ADP-ribose). Poly ADP-ribosylated polyoma virus minichromosome chromatin labeled in vivo with [3H]thymidine could be retained and eluted from anti-poly(ADP-ribose) immunoglobulin G-Sepharose. Pulse-labeled replicative intermediate minichromosomes were retained better on the antibody columns than were mature minichromosomes labeled for 2.5 h. The possible role of poly ADP-ribosylation of viral nucleosomes during polyoma replication or transcription is discussed.