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From the * Department of Medical Physics and Department of Radiation Oncology, Memorial
Sloan-Kettering Cancer Center, New York, 10021; Ku is a complex of two proteins, Ku70 and Ku80, and functions as a heterodimer to bind
DNA double-strand breaks (DSB) and activate DNA-dependent protein kinase. The role of
the Ku70 subunit in DNA DSB repair, hypersensitivity to ionizing radiation, and V(D)J recombination was examined in mice that lack Ku70 (Ku70
Los Alamos National Laboratory, Los Alamos,
New Mexico 87545; § Thomas Jefferson University, Philadelphia, Pennsylvania 19107;
Rockefeller
University, New York, 10021
/
). Like Ku80
/
mice, Ku70
/
mice showed a profound deficiency in DNA DSB repair and were proportional dwarfs. Surprisingly, in contrast to Ku80
/
mice in which both T and B lymphocyte development were
arrested at an early stage, lack of Ku70 was compatible with T cell receptor gene recombination and the development of mature CD4+CD8
and CD4
CD8+ T cells. Our data shows,
for the first time, that Ku70 plays an essential role in DNA DSB repair, but is not required for
TCR V(D)J recombination. These results suggest that distinct but overlapping repair pathways
may mediate DNA DSB repair and V(D)J recombination.
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