Nbs1 is essential for DNA repair by homologous recombination in higher vertebrate cells.
Double-strand breaks occur during DNA replication and are also induced by ionizing radiation. There are at least two pathways which can repair such breaks: non-homologous end joining and homologous recombination (HR). Although these pathways are essentially independent of one another, it is possible that the proteins Mre11, Rad50 and Xrs2 are involved in both pathways in Saccharomyces cerevisiae. In vertebrate cells, little is known about the exact function of the Mre11-Rad50-Nbs1 complex in the repair of double-strand breaks because Mre11- and Rad50-null mutations are lethal. Here we show that Nbs1 is essential for HR-mediated repair in higher vertebrate cells. The disruption of Nbs1 reduces gene conversion and sister chromatid exchanges, similar to other HR-deficient mutants. In fact, a site-specific double-strand break repair assay showed a notable reduction of HR events following generation of such breaks in Nbs1-disrupted cells. The rare recombinants observed in the Nbs1-disrupted cells were frequently found to have aberrant structures, which possibly arise from unusual crossover events, suggesting that the Nbs1 complex might be required to process recombination intermediates.
Tauchi
Hiroshi
H
Department of Environmental Sciences, Faculty of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki 310-8512 Japan. htauchi@mx.ibaraki.ac.jp
Kobayashi
Junya
J
Morishima
Ken-ichi
K
van Gent
Dik C
DC
Shiraishi
Takahiro
T
Verkaik
Nicole S
NS
vanHeems
Diana
D
Ito
Emi
E
Nakamura
Asako
A
Sonoda
Eiichiro
E
Takata
Minoru
M
Takeda
Shunichi
S
Matsuura
Shinya
S
Komatsu
Kenshi
K
D000818:Animals; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002645:Chickens; D002869:Chromosome Aberrations / Q000528:radiation effects; D004247:DNA / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D004249:DNA Damage / Q000528:radiation effects; D004260:DNA Repair; D004307:Dose-Response Relationship, Radiation; D005785:Gene Conversion; D017353:Gene Deletion; D017930:Genes, Reporter; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D011839:Radiation, Ionizing; D011995:Recombination, Genetic; D012854:Sister Chromatid Exchange
D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D004247:DNA