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pubmed:abstractText |
When rat pancreatic polynucleosomes were poly(ADP-ribosyl)ated with purified calf thymus poly(ADP-ribose) polymerase and examined by electron microscopy, a relaxation of their native zigzag structure was observed. At high ionic strengths control nucleosomes condensed into 250-A-thick fibers, but poly(ADP-ribosyl)ated polynucleosomes did not; they showed a close resemblance to chromatin depleted of histone H1. The relaxed state of poly(ADP-ribosyl)ated polynucleosomes was also confirmed by sedimentation velocity analysis. Histone H1 was found to be the major histone acceptor of poly(ADP-ribose). Poly(ADP-ribose) linked to histone H1 did not seem to cause its dissociation from the chromatin, but it impaired significantly its effect on chromatin condensation.
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