title: Nuclear protein modification and chromatin substructure. 3. Relationship between poly(adenosine diphosphate) ribosylation and different functional forms of chromatin.
abstract: The relationship between poly(adenosine diphosphate) ribosylation of nuclear proteins and functionally different forms of chromatin from mid-S-phase HeLa nuclei was investigated. The major observations emerging from this study were that unique nonhistone proteins were modified in mid-S-phase HeLa nuclei. The major acceptor for poly(adenosine diphosphate-ribose) [poly(ADP-Rib)] was an internucleosomal nonhistone protein (protein C; 125 000 molecular weight). Histones H3, H1, H2b, and H2a but not H4 were ADP-ribosylated in S-phase nuclei. Chromatin fragments preferentially released by micrococcal nuclease were enriched in nonhistone proteins, poly(ADP)-ribosylated nuclear proteins, poly(ADP-Rib) polymerase activity and nascent DNA from the DNA replicating fork. In extended forms of chromatin, contiguous to the DNA replicating fork, poly(ADP-Rib) polymerase was maximally active. However, in chromatin distal to the replicating fork (i.e., more condensed structures), nucleosomal histones and histone H1 were not significantly ADP-ribosylated, and poly(ADP-Rib) polymerase activity was depressed two- to threefold. The data suggest that a subset of nucleosomes in extended regions of chromatin is subject to extensive ADP ribosylation.
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism* / Q000648:ultrastructure; D006367:HeLa Cells / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008836:Micrococcal Nuclease; D009698:Nucleoproteins / Q000378:metabolism*; D009702:Nucleoside Diphosphate Sugars / Q000096:biosynthesis*; D011064:Poly Adenosine Diphosphate Ribose / Q000096:biosynthesis*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism
chemical_list: D002843:Chromatin; D006657:Histones; D009698:Nucleoproteins; D009702:Nucleoside Diphosphate Sugars; D011064:Poly Adenosine Diphosphate Ribose; D011065:Poly(ADP-ribose) Polymerases; D008836:Micrococcal Nuclease