MDC1 maintains genomic stability by participating in the amplification of ATM-dependent DNA damage signals

Mol Cell. 2006 Jan 20;21(2):187-200. doi: 10.1016/j.molcel.2005.11.025.


MDC1 functions in checkpoint activation and DNA repair following DNA damage. To address the physiological role of MDC1, we disrupted the MDC1 gene in mice. MDC1-/- mice recapitulated many phenotypes of H2AX-/- mice, including growth retardation, male infertility, immune defects, chromosome instability, DNA repair defects, and radiation sensitivity. At the molecular level, H2AX, MDC1, and ATM form a positive feedback loop, with MDC1 directly mediating the interaction between H2AX and ATM. MDC1 binds phosphorylated H2AX through its BRCT domain and ATM through its FHA domain. Through these interactions, MDC1 accumulates activated ATM flanking the sites of DNA damage, facilitating further ATM-dependent phosphorylation of H2AX and the amplification of DNA damage signals. In the absence of MDC1, many downstream ATM signaling events are defective. These results suggest that MDC1, as a signal amplifier of the ATM pathway, is vital in controlling proper DNA damage response and maintaining genomic stability.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Animals
  • Ataxia Telangiectasia Mutated Proteins
  • Cell Cycle Proteins / metabolism*
  • DNA Damage*
  • DNA Repair
  • DNA-Binding Proteins / metabolism*
  • Female
  • Genomic Instability
  • Infertility, Male / genetics
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Models, Biological
  • Nuclear Proteins / deficiency
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Protein Serine-Threonine Kinases / metabolism*
  • Signal Transduction
  • Trans-Activators
  • Tumor Suppressor Proteins / metabolism*


  • Adaptor Proteins, Signal Transducing
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • MDC1 protein, human
  • Nuclear Proteins
  • Trans-Activators
  • Tumor Suppressor Proteins
  • ATM protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • Atm protein, mouse
  • Protein Serine-Threonine Kinases