Identification of a defect in DNA ligase IV in a radiosensitive leukaemia patient.
The major mechanism for the repair of DNA double-strand breaks (DSBs) in mammalian cells is non-homologous end-joining (NHEJ), a process that involves the DNA-dependent protein kinase [1] [2], XRCC4 and DNA ligase IV [3] [4] [5] [6]. Rodent cells and mice defective in these components are radiation-sensitive and defective in V(D)J-recombination, showing that NHEJ also functions to rejoin DSBs introduced during lymphocyte development [7] [8]. 180BR is a radiosensitive cell line defective in DSB repair, which was derived from a leukaemia patient who was highly sensitive to radiotherapy [9] [10] [11]. We have identified a mutation within a highly conserved motif encompassing the active site in DNA ligase IV from 180BR cells. The mutated protein is severely compromised in its ability to form a stable enzyme-adenylate complex, although residual activity can be detected at high ATP concentrations. Our results characterize the first patient with a defect in an NHEJ component and suggest that a significant defect in NHEJ that leads to pronounced radiosensitivity is compatible with normal human viability and does not cause any major immune dysfunction. The defect, however, may confer a predisposition to leukaemia.
MRC Cell Mutation Unit, University of Sussex, Brighton, BN1 9RR, UK.
E
E
Riballo
S E
SE
Critchlow
S H
SH
Teo
A J
AJ
Doherty
A
A
Priestley
B
B
Broughton
B
B
Kysela
H
H
Beamish
N
N
Plowman
C F
CF
Arlett
A R
AR
Lehmann
S P
SP
Jackson
P A
PA
Jeggo
D000818:Animals; D015153:Blotting, Western; D002461:Cell Line, Transformed; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000235:genetics* / Q000378:metabolism; D004260:DNA Repair / Q000235:genetics; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000528:radiation effects; D006801:Humans; D009154:Mutation; D009687:Nuclear Proteins; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics* / Q000532:radiotherapy; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D011836:Radiation Tolerance / Q000235:genetics*; D011839:Radiation, Ionizing; D017422:Sequence Analysis, DNA
D004268:DNA-Binding Proteins; C000607893:LIG4 protein, human; D009687:Nuclear Proteins; C101467:XRCC4 protein, human; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D011088:DNA Ligases; D000072481:DNA Ligase ATP