Mycobacterial Ku and ligase proteins constitute a two-component NHEJ repair machine.
In mammalian cells, repair of DNA double-strand breaks (DSBs) by nonhomologous end-joining (NHEJ) is critical for genome stability. Although the end-bridging and ligation steps of NHEJ have been reconstituted in vitro, little is known about the end-processing reactions that occur before ligation. Recently, functionally homologous end-bridging and ligation activities have been identified in prokarya. Consistent with its homology to polymerases and nucleases, we demonstrate that DNA ligase D from Mycobacterium tuberculosis (Mt-Lig) possesses a unique variety of nucleotidyl transferase activities, including gap-filling polymerase, terminal transferase, and primase, and is also a 3' to 5' exonuclease. These enzyme activities allow the Mt-Ku and Mt-Lig proteins to join incompatible DSB ends in vitro, as well as to reconstitute NHEJ in vivo in yeast. These results demonstrate that prokaryotic Ku and ligase form a bona fide NHEJ system that encodes all the recognition, processing, and ligation activities required for DSB repair.
Della
Marina
M
Cambridge Institute for Medical Research, University of Cambridge, Department of Haematology, Hills Road, Cambridge CB2 2XY, UK.
Palmbos
Phillip L
PL
Tseng
Hui-Min
HM
Tonkin
Louise M
LM
Daley
James M
JM
Topper
Leana M
LM
Pitcher
Robert S
RS
Tomkinson
Alan E
AE
Wilson
Thomas E
TE
Doherty
Aidan J
AJ
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D004249:DNA Damage; D011088:DNA Ligases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004254:DNA Nucleotidyltransferases / Q000737:chemistry / Q000378:metabolism; D019915:DNA Primase / Q000737:chemistry / Q000378:metabolism; D004260:DNA Repair; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000378:metabolism; D005092:Exonucleases / Q000737:chemistry / Q000378:metabolism; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D017434:Protein Structure, Tertiary; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics
D001426:Bacterial Proteins; D004247:DNA; D004254:DNA Nucleotidyltransferases; D019915:DNA Primase; D004259:DNA-Directed DNA Polymerase; D005092:Exonucleases; D011088:DNA Ligases; C493173:DNA ligase D, Mycobacterium tuberculosis