Poly(ADP-ribose)-mediated post-translational modification of chromatin-associated human topoisomerase I. Inhibitory effects on catalytic activity

U. N. Kasid, B. Halligan, Leroy-Fong Liu, A. Dritschilo, M. Smulson

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We have investigated the association of human topoisomerase I with poly(ADP-ribosylation) domains of chromatin and the effects of this modification on the enzyme activity. In vitro poly(ADP-ribosylation) assays demonstrated that this enzyme was one of the major acceptors for this chromatin-dependent post-translational modification. Western blotting procedures using antibody to topoisomerase I indicated that under extensive poly(ADP-ribosylation) conditions, where a majority of poly(ADP-ribose) acceptor molecules form aggregates, the major population of the topoisomerase I associated with chromatin was apparently non-aggregated. The catalytic activity of the topoisomerase I associated with the poly(ADP-ribosylated) chromatin was 3-5-fold inhibited. Additionally, antibody to poly(ADP-ribose) was used to immunofractionate selectively the modified domains of chromatin. Our data suggests the presence of topoisomerase I, both adjacent and distal to the poly(ADP-ribosylated) sites of chromatin. Unmodified and a significant portion of the modified species of enzyme migrated as approximately 100-kDa proteins. However, the modified form of topoisomerase was noted to be catalytically less active as compared to the enzyme bound to the non-poly(ADP-ribosylated) nucleosomes. These results provide evidence, at the cellular level, for the poly(ADP-ribosylation)-mediated regulation of human topoisomerase I and suggest a functional significance for poly(ADP-ribosylation) in topoisomerase-related processes (replication, transcription, and recombination) in eukaryotes.

Original languageEnglish
Pages (from-to)18687-18692
Number of pages6
JournalJournal of Biological Chemistry
Issue number31
Publication statusPublished - 1989
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry


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