A dual interaction between the DNA damage response protein MDC1 and the RAG1 subunit of the V(D)J recombinase

J Biol Chem. 2012 Oct 19;287(43):36488-98. doi: 10.1074/jbc.M112.402487. Epub 2012 Aug 31.


The first step in V(D)J recombination is the formation of specific DNA double-strand breaks (DSBs) by the RAG1 and RAG2 proteins, which form the RAG recombinase. DSBs activate a complex network of proteins termed the DNA damage response (DDR). A key early event in the DDR is the phosphorylation of histone H2AX around DSBs, which forms a binding site for the tandem BRCA1 C-terminal (tBRCT) domain of MDC1. This event is required for subsequent signal amplification and recruitment of additional DDR proteins to the break site. RAG1 bears a histone H2AX-like motif at its C terminus (R1Ct), making it a putative MDC1-binding protein. In this work we show that the tBRCT domain of MDC1 binds the R1Ct motif of RAG1. Surprisingly, we also observed a second binding interface between the two proteins that involves the Proline-Serine-Threonine rich (PST) repeats of MDC1 and the N-terminal non-core region of RAG1 (R1Nt). The repeats-R1Nt interaction is constitutive, whereas the tBRCT-R1Ct interaction likely requires phosphorylation of the R1Ct motif of RAG1. As the C terminus of RAG1 has been implicated in inhibition of RAG activity, we propose a model in which phosphorylation of the R1Ct motif of RAG1 functions as a self-initiated regulatory signal.

Publication types

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

MeSH terms

  • Amino Acid Motifs
  • BRCA1 Protein / genetics
  • BRCA1 Protein / metabolism
  • Cell Line, Tumor
  • Histones / genetics
  • Histones / metabolism
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism*
  • Humans
  • Models, Biological*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Peptide Mapping / methods
  • Phosphorylation
  • Protein Structure, Tertiary
  • Repetitive Sequences, Amino Acid
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • VDJ Recombinases / genetics
  • VDJ Recombinases / metabolism*


  • BRCA1 Protein
  • BRCA1 protein, human
  • Histones
  • Homeodomain Proteins
  • MDC1 protein, human
  • Nuclear Proteins
  • Trans-Activators
  • RAG-1 protein
  • VDJ Recombinases