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Nuclear protein modification and chromatin substructure. 3. Relationship between poly(adenosine diphosphate) ribosylation and different functional forms of chromatin.

Authors
Type
Published Article
Journal
Biochemistry
Publication Date
Volume
18
Issue
6
Pages
983–990
Identifiers
PMID: 106878
Source
Medline

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.

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