Nibrin is a protein associated with the repair of double strand breaks(DSBs) which pose serious damage to a genome. It is a 754 amino acid protein identified as a member of the NBS1/hMre11/RAD50(N/M/R, more commonly referred to as MRN) double strand DNA break repair complex.This complex recognizes DNA damage and rapidly relocates to DSB sites and forms nuclear foci. It also has a role in regulation of N/M/R (MRN) protein complex activity which includes end-processing of both physiological and mutagenic DNA double strand breaks (DSBs).Cellular response is performed by damage sensors, effectors of lesion repair and signal transduction. The central role is carried out by ataxia-telangiectasia mutated(ATM) by activating the DSB signaling cascade, phosphorylating downstream substrates such as histone H2AX and NBS1.