title: A dual interaction between the DNA damage response protein MDC1 and the RAG1 subunit of the V(D)J recombinase.
abstract: 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.
authors.affiliation: Department of Genetics, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel.
authors.forename: Gideon
authors.initials: G
authors.lastname: Coster
authors.forename: Ayala
authors.initials: A
authors.lastname: Gold
authors.forename: Darlene
authors.initials: D
authors.lastname: Chen
authors.forename: David G
authors.initials: DG
authors.lastname: Schatz
authors.forename: Michal
authors.initials: M
authors.lastname: Goldberg
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020816:Amino Acid Motifs; D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D006657:Histones / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008954:Models, Biological; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010449:Peptide Mapping / Q000379:methods; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D020449:Repetitive Sequences, Amino Acid; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D045567:VDJ Recombinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D018797:Cell Cycle Proteins; D006657:Histones; D018398:Homeodomain Proteins; C413163:MDC1 protein, human; D009687:Nuclear Proteins; D015534:Trans-Activators; C064658:RAG-1 protein; D045567:VDJ Recombinases