Nibrin (NBN)

Part of the MRE11-RAD50-NBN (MRN complex) which plays a vital role in the cellular response to DNA damage and the maintenance of chromosome integrity. The complex possesses single-strand endonuclease activity and double-strand-specific 3'-5' exonuclease activity, which are provided by MRE11.

RAD50 may be required to bind DNA ends and hold them in close proximity. NBN modulate the DNA damage signal sensing by recruitment PI3/PI4-kinase family members ATM, ATR, and probably DNA-PKcs to the DNA damage sites and activating their functions.