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ubiquitin protein ligase E3 component n-recognin 2 OKDB#: 5731
 Symbols: UBR2 Species: human
 Synonyms: C6orf133, bA49A4.1, dJ242G1.1, dJ392M17.3  Locus: 6p21.1 in Homo sapiens


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General Comment NCBI Summary: This gene encodes an E3 ubiquitin ligase of the N-end rule proteolytic pathway that targets proteins with destabilizing N-terminal residues for polyubiquitylation and proteasome-mediated degradation. Alternative splicing results in multiple transcript variants.[provided by RefSeq, May 2010]
General function DNA repair, Enzyme
Comment
Cellular localization
Comment
Ovarian function Oocyte maturation
Comment Tex19.1 inhibits the N-end rule pathway and maintains acetylated SMC3 cohesin and sister chromatid cohesion in oocytes. Reichmann J et al. (2020) Age-dependent oocyte aneuploidy, a major cause of Down syndrome, is associated with declining sister chromatid cohesion in postnatal oocytes. Here we show that cohesion in postnatal mouse oocytes is regulated by Tex19.1. We show Tex19.1-/- oocytes have defects maintaining chiasmata, missegregate their chromosomes during meiosis, and transmit aneuploidies to the next generation. Furthermore, we show that mouse Tex19.1 inhibits N-end rule protein degradation mediated by its interacting partner UBR2, and that Ubr2 itself has a previously undescribed role in negatively regulating the acetylated SMC3 subpopulation of cohesin in mitotic somatic cells. Lastly, we show that acetylated SMC3 is associated with meiotic chromosome axes in mouse oocytes, and that this population of cohesin is specifically depleted in the absence of Tex19.1. These findings indicate that Tex19.1 regulates UBR protein activity to maintain acetylated SMC3 and sister chromatid cohesion in postnatal oocytes and prevent aneuploidy from arising in the female germline.//////////////////
Expression regulated by
Comment
Ovarian localization Oocyte, Granulosa
Comment
Follicle stages
Comment
Phenotypes
Mutations 3 mutations

Species: mouse
Mutation name:
type: null mutation
fertility: infertile - ovarian defect
Comment: Loss of Ubr2, an E3 ubiquitin ligase, leads to chromosome fragility and impaired homologous recombinational repair. Ouyang Y et al. (2006) 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.//////////////////

Species: mouse
Mutation name:
type: null mutation
fertility: embryonic lethal
Comment: Female lethality and apoptosis of spermatocytes in mice lacking the UBR2 ubiquitin ligase of the N-end rule pathway. Kwon YT et al. (2003) Substrates of the ubiquitin-dependent N-end rule pathway include proteins with destabilizing N-terminal residues. UBR1(-/-) mice, which lacked the pathway's ubiquitin ligase E3alpha, were viable and retained the N-end rule pathway. The present work describes the identification and analysis of mouse UBR2, a homolog of UBR1. We demonstrate that the substrate-binding properties of UBR2 are highly similar to those of UBR1, identifying UBR2 as the second E3 of the mammalian N-end rule pathway. UBR2(-/-) mouse strains were constructed, and their viability was found to be dependent on both gender and genetic background. In the strain 129 (inbred) background, the UBR2(-/-) genotype was lethal to most embryos of either gender. In the 129/B6 (mixed) background, most UBR2(-/-) females died as embryos, whereas UBR2(-/-) males were viable but infertile, owing to the postnatal degeneration of the testes. The gross architecture of UBR2(-/-) testes was normal and spermatogonia were intact as well, but UBR2(-/-) spermatocytes were arrested between leptotene/zygotene and pachytene and died through apoptosis. A conspicuous defect of UBR2(-/-) spermatocytes was the absence of intact synaptonemal complexes. We conclude that the UBR2 ubiquitin ligase and, hence, the N-end rule pathway are required for male meiosis and spermatogenesis and for an essential aspect of female embryonic development.//////////////////

Species: None
Mutation name:
type: None
fertility: None
Comment:

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created: March 13, 2020, 12:05 p.m. by: system   email:
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last update: April 9, 2020, 2:08 p.m. by: hsueh    email:



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