Loss of Ubr2, an E3 ubiquitin ligase, leads to chromosome fragility and impaired homologous recombinational repair.
The N-end rule pathway of protein degradation targets proteins with destabilizing N-terminal residues. Ubr2 is one of the E3 ubiquitin ligases of the mouse N-end rule pathway. We have previously shown that Ubr2-/- male mice are infertile, owing to the arrest of spermatocytes between the leptotene/zygotene and pachytene of meiosis I, the failure of chromosome pairing, and subsequent apoptosis. Here, we report that mouse fibroblast cells derived from Ubr2-/- embryos display genome instability. The frequency of chromosomal bridges and micronuclei were much higher in Ubr2-/- fibroblasts than in +/+ controls. Metaphase chromosome spreads from Ubr2-/- cells revealed a high incidence of spontaneous chromosomal gaps, indicating chromosomal fragility. These fragile sites were generally replicated late in S phase. Ubr2-/- cells were hypersensitive to mitomycin C, a DNA cross-linking agent, but displayed normal sensitivity to gamma-irradiation. A reporter assay showed that Ubr2-/- cells are significantly impaired in the homologous recombination repair of a double strand break. In contrast, Ubr2-/- cells appeared normal in an assay for non-homologous end joining. Our results therefore unveil the role of the ubiquitin ligase Ubr2 in maintaining genome integrity and in homologous recombination repair.
Ouyang
Yan
Y
Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
Kwon
Yong Tae
YT
An
Jee Young
JY
Eller
Danny
D
Tsai
Shih-Chang
SC
Diaz-Perez
Silvia
S
Troke
Joshua J
JJ
Teitell
Michael A
MA
Marahrens
York
Y
D000818:Animals; D002478:Cells, Cultured; D002873:Chromosome Fragility / Q000235:genetics*; D004249:DNA Damage / Q000235:genetics; D004260:DNA Repair / Q000235:genetics*; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000502:physiology; D017930:Genes, Reporter; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D011995:Recombination, Genetic; D044767:Ubiquitin-Protein Ligases / Q000172:deficiency* / Q000235:genetics*
C511160:UBR2 protein, mouse; D044767:Ubiquitin-Protein Ligases