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  • Title: A murine model of Nijmegen breakage syndrome.
    Author: Williams BR, Mirzoeva OK, Morgan WF, Lin J, Dunnick W, Petrini JH.
    Journal: Curr Biol; 2002 Apr 16; 12(8):648-53. PubMed ID: 11967151.
    Abstract:
    Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder characterized by microcephaly, immunodeficiency, and predisposition to hematopoietic malignancy. The clinical and cellular phenotypes of NBS substantially overlap those of ataxia-telangiectasia (A-T). NBS is caused by mutation of the NBS1 gene, which encodes a member of the Mre11 complex, a trimeric protein complex also containing Mre11 and Rad50. Several lines of evidence indicate that the ataxia-telangiectasia mutated (ATM) kinase and the Mre11 complex functionally interact. Both NBS and A-T cells exhibit ionizing radiation (IR) sensitivity and defects in the intra S phase checkpoint, resulting in radioresistant DNA synthesis (RDS)-the failure to suppress DNA replication origin firing after IR exposure. NBS1 is phosphorylated by ATM in response to IR, and this event is required for activation of the intra S phase checkpoint (the RDS checkpoint). We derived a murine model of NBS, the Nbs1(DeltaB/DeltaB) mouse. Nbs1(DeltaB/DeltaB) cells are phenotypically identical to those established from NBS patients. The Nbs1(DeltaB) allele was synthetically lethal with ATM deficiency. We propose that the ATM-Mre11 complex DNA damage response pathway is essential and that ATM or the Mre11 complex serves as a nexus to additional components of the pathway.
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