DNA strand breaks alter histone ADP-ribosylation.
Histone ADP-ribosylation was studied using two-dimensional gel electrophoresis after cleavage of the nuclear DNA with nucleases. Modified histones carrying different numbers of ADP-ribose groups form a ladder of bands above each variant histone. Cellular lysates containing unfragmented DNA mainly synthesize mono(ADP-ribosylated) histones. Cleavage of the DNA with either DNase I or micrococcal nuclease to fragments of an average size of 10-20 kilobases (kb) dramatically induces the formation of poly(ADP-ribosylated) species of histones in nuclei. As the number of DNA strand breaks produced by either DNase I or micrococcal nuclease increases and a great number of DNA cuts is introduced (fragments of 0.4-0.2 kb), the size of the poly(ADP-ribose) chains on the histones decreases. Finally, in the presence of 10 mM cAMP as an inhibitor of poly(ADP-ribose) glycohydrolase, human lymphoid nuclei synthesize hyper(ADP-ribosylated) histone H2B with at least 40 ADP-ribose groups attached to it. Lateral ladders emanating at precise points of the linear ladder on hypermodified H2B can arise from branching of poly(ADP-ribose) or from multiple monomodifications of glutamic (or aspartic) acid residues. Branching or de novo monomodifications occur after a precise number of ADP-ribose groups have been added to a histone molecule. Poly(ADP-ribosylated) histones thus appear to be intermediates in nuclear processes involving DNA strand breaks.
Boulikas
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Départment de Biochimie, Faculté de Médecine, Université de Sherbrooke, PQ, Canada.
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004249:DNA Damage; D003850:Deoxyribonuclease I / Q000494:pharmacology; D015180:Electrophoresis, Gel, Two-Dimensional; D006657:Histones / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D014407:Tumor Cells, Cultured
D002843:Chromatin; D006657:Histones; D000246:Adenosine Diphosphate Ribose; D003850:Deoxyribonuclease I