Rag mutations reveal robust alternative end joining.
Mammalian cells repair DNA double-strand breaks (DSBs) through either homologous recombination or non-homologous end joining (NHEJ). V(D)J recombination, a cut-and-paste mechanism for generating diversity in antigen receptors, relies on NHEJ for repairing DSBs introduced by the Rag1-Rag2 protein complex. Animals lacking any of the seven known NHEJ factors are therefore immunodeficient. Nevertheless, DSB repair is not eliminated entirely in these animals: evidence of a third mechanism, 'alternative NHEJ', appears in the form of extremely rare V(D)J junctions and a higher rate of chromosomal translocations. The paucity of these V(D)J events has suggested that alternative NHEJ contributes little to a cell's overall repair capacity, being operative only (and inefficiently) when classical NHEJ fails. Here we find that removing certain portions of murine Rag proteins reveals robust alternative NHEJ activity in NHEJ-deficient cells and some alternative joining activity even in wild-type cells. We propose a two-tier model in which the Rag proteins collaborate with NHEJ factors to preserve genomic integrity during V(D)J recombination.
Corneo
Barbara
B
The Kimmel Center for Biology and Medicine of the Skirball Institute and Department of Pathology, New York University School of Medicine, New York, New York 10016, USA.
Wendland
Rebecca L
RL
Deriano
Ludovic
L
Cui
Xiaoping
X
Klein
Isaac A
IA
Wong
Serre-Yu
SY
Arnal
Suzzette
S
Holub
Abigail J
AJ
Weller
Geoffrey R
GR
Pancake
Bette A
BA
Shah
Sundeep
S
Brandt
Vicky L
VL
Meek
Katheryn
K
Roth
David B
DB
D000818:Animals; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism*; D018398:Homeodomain Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008957:Models, Genetic; D009154:Mutation / Q000235:genetics; D011995:Recombination, Genetic / Q000235:genetics*
D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C499308:Rag2 protein, mouse; C511788:XRCC4 protein, mouse; C064658:RAG-1 protein