forkhead associated (FHA) domain found in nibrin and similar proteins
Nibrin (NBN), also called cell cycle regulatory protein p95, or Nijmegen breakage syndrome protein 1 (NBS1), is a novel DNA double-strand break repair protein that is mutated in Nijmegen breakage syndrome. It is a component of the MRE11-RAD50-NBN (MRN complex) which plays a critical role in the cellular response to DNA damage and the maintenance of chromosome integrity. Nibrin modulates the DNA damage signal sensing by recruiting PI3/PI4-kinase family members ATM, ATR, and probably DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to the DNA damage sites and activating their functions. It can also recruit MRE11 and RAD50 to the proximity of DSBs by an interaction with the histone H2AX. Nibrin also functions in telomere length maintenance by generating the 3' overhang which serves as a primer for telomerase dependent telomere elongation. Nibrin is a major player in the control of intra-S-phase checkpoint. This subfamily also includes Schizosaccharomyces pombe DNA repair and telomere maintenance protein Nbs1 and Arabidopsis thaliana AtNbs1. SpNbs1 is an FHA domain-containing protein required for DNA damage repair and S-phase DNA damage checkpoint. It is involved in telomere length maintenance and maintenance of chromatin structure. AtNbs1 is a component of MRN complex. It also functions in the very early stages of meiosis. The FHA domain is a small phosphopeptide recognition module.
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