Resistance of ADP-ribosylated histones and HMG proteins to proteases.
Calf thymus histones (individually isolated or mixtures) and high mobility group proteins were ADP-ribosylated in vitro using [32P]NAD+ and immobilized purified poly(ADP-ribose) polymerase. The modified histones were then subjected to V8 protease or alpha-chymotrypsin digestion and the resulting peptides were separated by electrophoresis on acetic acid-urea-Triton gels. It was found that in vitro ADP-ribosylated histones were much more resistant to proteases than unmodified histones. A similar approach was applied to histones modified by the endogenous poly(ADP-ribose) polymerase in permeabilized NS-1 mouse myeloma cells in culture. In this case, the proteases could not discriminate between modified and unmodified histones and putative mono(ADP-ribosyl)ated peptides appeared in a digestion frame corresponding to that of bulk peptides. These differences are most probably due to the specificity or number of ADP-ribose groups added to the histones by the endogenous or exogenous poly(ADP-ribose) polymerase. Thus, depending on the size of poly(ADP-ribose) attached to nuclear proteins, these modified proteins might display different degrees of resistance to proteolysis.
Boulikas
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Linus Pauling Institute of Science and Medicine, Palo Alto, CA 94306.
Poirier
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D036002:ADP Ribose Transferases; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002918:Chymotrypsin / Q000378:metabolism*; D006609:High Mobility Group Proteins / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D051379:Mice; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012697:Serine Endopeptidases / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D006609:High Mobility Group Proteins; D006657:Histones; D000246:Adenosine Diphosphate Ribose; D036002:ADP Ribose Transferases; D011065:Poly(ADP-ribose) Polymerases; D012697:Serine Endopeptidases; D002918:Chymotrypsin; C028344:glutamyl endopeptidase