TY - JOUR
T1 - Role of the DNA ligase III zinc finger in polynucleotide binding and ligation
AU - Taylor, Richard M.
AU - Whitehouse, Jenna
AU - Cappelli, Enrico
AU - Frosina, Guido
AU - Caldecott, Keith W.
PY - 1998/11/1
Y1 - 1998/11/1
N2 - 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.
AB - 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.
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U2 - 10.1093/nar/26.21.4804
DO - 10.1093/nar/26.21.4804
M3 - Article
C2 - 9776738
AN - SCOPUS:0032212128
VL - 26
SP - 4804
EP - 4810
JO - Nucleic Acids Research
JF - Nucleic Acids Research
SN - 0305-1048
IS - 21
ER -