Zhao, S. et al. Functional link between ataxia-telangiectasia and Nijmegen breakage syndrome gene products. Nature 405, 473-477

Department of Molecular Medicine/Institute of Biotechnology, The University of Texas Health Science Center at San Antonio, 78245-3207, USA.
Nature (Impact Factor: 42.35). 05/2000; 405(6785):473-477. DOI: 10.1038/35013083

ABSTRACT Ataxia telangiectasia (A-T) and Nijmegen breakage syndrome (NBS) are recessive genetic disorders with susceptibility to cancer and similar cellular phenotypes. The protein product of the gene responsible for A-T, designated ATM, is a member of a family of kinases characterized by a carboxy-terminal phosphatidylinositol 3-kinase-like domain. The NBS1 protein is specifically mutated in patients with Nijmegen breakage syndrome and forms a complex with the DNA repair proteins Rad50 and Mre11. Here we show that phosphorylation of NBS1, induced by ionizing radiation, requires catalytically active ATM. Complexes containing ATM and NBS1 exist in vivo in both untreated cells and cells treated with ionizing radiation. We have identified two residues of NBS1, Ser 278 and Ser 343 that are phosphorylated in vitro by ATM and whose modification in vivo is essential for the cellular response to DNA damage. This response includes S-phase checkpoint activation, formation of the NBS1/Mre11/Rad50 nuclear foci and rescue of hypersensitivity to ionizing radiation. Together, these results demonstrate a biochemical link between cell-cycle checkpoints activated by DNA damage and DNA repair in two genetic diseases with overlapping phenotypes.

Download full-text


Available from: Jerry W Shay, Jun 24, 2014
1 Follower
  • Source
    • "Several investigations suggest that the Mre11-Rad50-Nbs1 (MRN) complex is involved in ATM activation and recruitment to the sites of DSBs (Uziel et al, 2003; Cerosaletti & Concannon, 2004), because attenuated activation and no recruitment of ATM to DSBs upon damage were found in Mre11-and Nbs1-deficient cell lines. Earlier studies have shown that MRN lies downstream of the ATM mediated DNA damage signalling pathway because ATM can phosphorylate the components of the MRN complex in response to IR (Lim & Ki, 2000; Wu & Ranganathan, 2000; Zhao & Weng, 2000). However, further analyses demonstrate that the MRN complex is more like an upper actor of ATM pathway (Uziel et al, 2003;Difilippantonio et al, 2005; Carson et al, 2003). "
    DNA Replication-Current Advances, 08/2011; , ISBN: 978-953-307-593-8
  • Source
    • "The middle part of the NBS1 protein consists of a series of phosphorylation sites, which are specific targets of the ATM kinase. However, the function of these phosphorylation sites in DDR, especially of the DDR downstream effectors, CHK2 and SMC1 phosphorylation, is controversially discussed (Wu et al., 2000; Zhao et al., 2000; Buscemi et al., 2001; Kim et al., 2002; Yazdi et al., 2002; Lee et al., 2003; Lee and Paull, 2005; Difilippantonio et al., 2007). Using gene targeting technology, a point mutation was introduced into the Nbs1 T278 site that abolishes phosphorylation and the Nbs1 T278A mutant protein expressed at a physiological level in mice. "
    [Show abstract] [Hide abstract]
    ABSTRACT: NBS1, mutated in Nijmegen breakage syndrome (NBS), senses the DNA double strand breaks (DSBs) and initiates the DNA damage response (DDR) by activating ATM kinase. Meanwhile, NBS1 is phosphorylated by ATM at Serine 278 and Serine 343 and thereby assists the activation of the ATM downstream targets. To study the physiological function of the Nbs1 phosphorylation, we have knocked in a point mutation in the moue genome that results in the replacement of Threonine 278 (equivalent to the human Serine 278) by Alanine. The Nbs1(T278A) knock-in mice develop normally and show no gross defects. The mutation of this phosphorylation site does not affect the proliferation or genomic stability. Ionizing radiation (IR) of primary Nbs1(T278A) MEFs reveals no obvious defects in the Chk2 phosphorylation at 1Gy, but a delayed phosphorylation of Chk2 and Smc1 only at intermediate (4.5Gy) and high (10Gy) doses, respectively. In contrast to Serine 343 mutant, Threonine 278 mutation has no effect on the HU-induced ATR-Chk1 activation. Our study thus shows that Nbs1 phosphorylation at the Threonine 278 is dispensable for mouse development and plays a differential function in assisting the DDR of downstream effectors in vivo, depending on the doses of DNA damage.
    Mechanisms of ageing and development 06/2011; 132(8-9):382-8. DOI:10.1016/j.mad.2011.05.001 · 3.51 Impact Factor
  • Source
    • " . Loss of p38γ led to abrogation of phosphorylation of NBS1 at Ser343 and phosphorylation of p53 at Ser15 ( Fig . 3D ) , both of which have been shown to be direct substrate sites of ATM / ATR and are crucial for activation of these proteins , respectively ( Tibbetts et al . , 1999 ; Gatei et al . , 2000 ; Lim et al . , 2000 ; Wu et al . , 2000 ; Zhao et al . , 2000 ) ."
    [Show abstract] [Hide abstract]
    ABSTRACT: In eukaryotic cells, DNA damage triggers activation of checkpoint signaling pathways that coordinate cell cycle arrest and repair of damaged DNA. These DNA damage responses serve to maintain genome stability and prevent accumulation of genetic mutations and development of cancer. The p38 MAPK was previously implicated in cellular responses to several types of DNA damage. However, the role of each of the four p38 isoforms and the mechanism for their involvement in DNA damage responses remained poorly understood. In this study, we demonstrate that p38γ, but not the other p38 isoforms, contributes to the survival of UV-treated cells. Deletion of p38γ sensitizes cells to UV exposure, accompanied by prolonged S phase cell cycle arrest and increased rate of apoptosis. Further investigation reveal that p38γ is essential for the optimal activation of the checkpoint signaling caused by UV, and for the efficient repair of UV-induced DNA damage. These findings have established a novel role of p38γ in UV-induced DNA damage responses, and suggested that p38γ contributes to the ability of cells to cope with UV exposure by regulating the checkpoint signaling pathways and the repair of damaged DNA.
    Protein & Cell 06/2010; 1(6):573-83. DOI:10.1007/s13238-010-0075-1 · 2.85 Impact Factor
Show more