DNA ligase III is recruited to DNA strand breaks by a zinc finger motif homologous to that of poly(ADP-ribose) polymerase. Identification of two functionally distinct DNA binding regions within DNA ligase III.
Mammalian DNA ligases are composed of a conserved catalytic domain flanked by unrelated sequences. At the C-terminal end of the catalytic domain, there is a 16-amino acid sequence, known as the conserved peptide, whose role in the ligation reaction is unknown. Here we show that conserved positively charged residues at the C-terminal end of this motif are required for enzyme-AMP formation. These residues probably interact with the triphosphate tail of ATP, positioning it for nucleophilic attack by the active site lysine. Amino acid residues within the sequence RFPR, which is invariant in the conserved peptide of mammalian DNA ligases, play critical roles in the subsequent nucleotidyl transfer reaction that produces the DNA-adenylate intermediate. DNA binding by the N-terminal zinc finger of DNA ligase III, which is homologous with the two zinc fingers of poly(ADP-ribose) polymerase, is not required for DNA ligase activity in vitro or in vivo. However, this zinc finger enables DNA ligase III to interact with and ligate nicked DNA at physiological salt concentrations. We suggest that in vivo the DNA ligase III zinc finger may displace poly(ADP-ribose) polymerase from DNA strand breaks, allowing repair to occur.
Department of Molecular Medicine, Institute of Biotechnology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78245, USA.
Z B
ZB
Mackey
C
C
Niedergang
J M
JM
Murcia
J
J
Leppard
K
K
Au
J
J
Chen
G
G
de Murcia
A E
AE
Tomkinson
D000249:Adenosine Monophosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D020134:Catalytic Domain; D017124:Conserved Sequence; D018983:DNA Footprinting; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000737:chemistry* / Q000378:metabolism*; D004260:DNA Repair; D003850:Deoxyribonuclease I; D006801:Humans; D008239:Lysine; D008322:Mammals; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011065:Poly(ADP-ribose) Polymerases / Q000737:chemistry* / Q000378:metabolism*; D000075223:Poly-ADP-Ribose Binding Proteins; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D029867:Xenopus Proteins; D016335:Zinc Fingers
D000075223:Poly-ADP-Ribose Binding Proteins; D011994:Recombinant Proteins; D029867:Xenopus Proteins; D000249:Adenosine Monophosphate; D000255:Adenosine Triphosphate; D011065:Poly(ADP-ribose) Polymerases; D003850:Deoxyribonuclease I; D011088:DNA Ligases; D000072481:DNA Ligase ATP; C000618816:DNA ligase III alpha protein, Xenopus; C000618817:LIG3 protein, human; D008239:Lysine