Nbs1 is required for ATR-dependent phosphorylation events

EMBO J. 2005 Jan 12;24(1):199-208. doi: 10.1038/sj.emboj.7600504. Epub 2004 Dec 16.

Abstract

Nijmegen breakage syndrome (NBS) is characterised by microcephaly, developmental delay, characteristic facial features, immunodeficiency and radiosensitivity. Nbs1, the protein defective in NBS, functions in ataxia telangiectasia mutated protein (ATM)-dependent signalling likely facilitating ATM phosphorylation events. While NBS shares overlapping characteristics with ataxia telangiectasia, it also has features overlapping with ATR-Seckel (ATR: ataxia-telangiectasia and Rad3-related protein) syndrome, a subclass of Seckel syndrome mutated in ATR. We show that Nbs1 also facilitates ATR-dependent phosphorylation. NBS cell lines show a similar defect in ATR phosphorylation of Chk1, c-jun and p-53 in response to UV irradiation- and hydroxyurea (HU)-induced replication stalling. They are also impaired in ubiquitination of FANCD2 after HU treatment, which is ATR dependent. Following HU-induced replication arrest, NBS and ATR-Seckel cells show similarly impaired G2/M checkpoint arrest and an impaired ability to restart DNA synthesis at stalled replication forks. Moreover, NBS cells fail to retain ATR in the nucleus following HU treatment and extraction. Our findings suggest that Nbs1 functions in both ATR- and ATM-dependent signalling. We propose that the NBS clinical features represent the result of these combined defects.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Ataxia Telangiectasia Mutated Proteins
  • Cell Cycle / physiology
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cells, Cultured
  • DNA Damage*
  • DNA Repair
  • DNA Replication
  • Fanconi Anemia Complementation Group D2 Protein
  • Fibroblasts / cytology
  • Fibroblasts / drug effects
  • Fibroblasts / metabolism
  • Fibroblasts / radiation effects
  • Humans
  • Hydroxyurea / pharmacology
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Nucleic Acid Synthesis Inhibitors / pharmacology
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Signal Transduction / physiology
  • Syndrome
  • Ubiquitin / metabolism
  • Ultraviolet Rays

Substances

  • Cell Cycle Proteins
  • FANCD2 protein, human
  • Fanconi Anemia Complementation Group D2 Protein
  • NBN protein, human
  • Nuclear Proteins
  • Nucleic Acid Synthesis Inhibitors
  • Ubiquitin
  • ATR protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • Protein-Serine-Threonine Kinases
  • Hydroxyurea