Nijmegen breakage syndrome (NBS) is characterized by extreme radiation sensitivity, chromosomal instability and cancer. These phenotypes are similar to those of ataxia telangiectasia mutated (ATM) disease, where there is a deficiency in a protein kinase that is activated by DNA damage, indicating that the NBS1 (Nibrin) and ATM proteins may participate in common pathways. Nibrin is specifically phosphorylated in response to gamma-radiation, ultraviolet light and exposure to hydroxyurea. The phosphorylation of Nibrin requires catalytically active ATM. ATM physically interacts with and phosphorylates Nibrin on Serine 343 both in vitro and in vivo. Serine 343 is phosphorylated in vitro by ATM and the modification of this residue in vivo is essential for the cellular response to DNA damage. This response includes S-phase checkpoint activation, formation of the NBS1/Mrel1/Rad50 nuclear foci and rescue of hypersensitivity to ionizing radiation.
Background References
1. Kefala M et al. Increased expression of phosphorylated NBS1, a key molecule of the DNA damage response machinery, is an adverse prognostic factor in patients with de novo myelodysplastic syndromes. Leuk Res 37:1576-82 (2013).
2. Cherubini G et al. The FANC pathway is activated by adenovirus infection and promotes viral replication-dependent recombination. Nucleic Acids Res : (2011).
Tissue Specificity
Ubiquitous. Expressed at high levels in testis.
Post-translational Modification
Phosphorylated by ATM in response of ionizing radiation, and such phosphorylation is responsible intra-S phase checkpoint control and telomere maintenance.
Western blot analysis of Phospho-p95/NBS1 (S343) on different lysates with Rabbit anti-Phospho-p95/NBS1 (S343) antibody (ET1607-5) at 1/1,000 dilution.
Lane 1: HeLa whole cell lysate (20 µg/Lane) Lane 2: HeLa treated with 20μM Etoposide for 2 hours whole cell lysate (20 µg/Lane) Lane 3: Jurkat whole cell lysate (20 µg/Lane) Lane 4: Jurkattreated with 25μM Etoposide for 5 hours whole cell lysate (20 µg/Lane)
Predicted band size: 85 kDa Observed band size: 95 kDa Exposure time: 5 minutes; 4-20% SDS-PAGE gel.
Proteins were transferred to a PVDF membrane and blocked with 5% NFDM/TBST for 1 hour at room temperature. The primary antibody (ET1607-5) at 1/1,000 dilution was used in 5% NFDM/TBST at room temperature for 2 hours. Goat Anti-Rabbit IgG - HRP Secondary Antibody (HA1001) at 1/50,000 dilution was used for 1 hour at room temperature.
Immunohistochemical analysis of paraffin-embedded mouse testis tissue using anti-Phospho-p95/NBS1 (S343) antibody. The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 8.0-8.4) for 20 minutes.The tissues were blocked in 5% BSA for 30 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (ET1607-5, 1/50) for 30 minutes at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
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