Role of the DNA ligase III zinc finger in polynucleotide binding and ligation

Richard M. Taylor, Jenna Whitehouse, Enrico Cappelli, Guido Frosina, Keith W. Caldecott

Research output: Contribution to journalArticlepeer-review

Abstract

Mammalian DNA ligase III exists as two distinct isoforms denoted α and β. Both forms possess a motif that is homologous to the putative zinc finger present in poly(ADP-ribose) polymerase. Here, the role of this motif in the binding and ligation of nicked DNA and RNA substrates in vitro has been examined in both isoforms. Disruption of the putative zinc finger did not affect DNA ligase III activity on nicked DNA duplex, nor did it abolish DNA ligase III-α activity during DNA base excision repair in a cell-free assay. In contrast, disruption of this motif reduced 3-fold the activity of both DNA ligase III isoforms on nicked RNA present in RNA/DNA homopolymers. Furthermore, whereas disruption of the motif did not prevent binding of DNA ligase III to nicked DNA duplex, binding to nicked RNA homopolymers was reduced ~ 10-fold. These results suggest that the putative zinc finger does not stimulate DNA ligase III activity on simple nicked DNA substrates, but indicate that this motif can target the binding and activity of DNA ligase III to nicked RNA homopolymer. The implications of these results to the cellular role of the putative zinc finger are discussed.

Original languageEnglish
Pages (from-to)4804-4810
Number of pages7
JournalNucleic Acids Research
Volume26
Issue number21
DOIs
Publication statusPublished - Nov 1 1998

ASJC Scopus subject areas

  • Genetics

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