Plays a role in the cellular response to DNA damage and the maintenance of genome stability through its association with the MRN damage-sensing complex (PubMed:27568553). Promotes chromatin loading and activity of the MRN complex to facilitate subsequent ATM-mediated DNA damage response signaling and DNA repair (PubMed:27568553). Associates with the MRE11-RAD50-NBN (MRN) damage-sensing complex; this association is constitutive (PubMed:27568553). Interacts with MRE11 (PubMed:27568553). Interacts with NBN (PubMed:27568553). Interacts with RAD50 (PubMed:27568553). Recruited to sites of DNA damage (PubMed:27568553). Phosphorylation on Ser-115 induces its nuclear localization and promotes genome stability (PubMed:27568553). Phosphorylated; phosphorylation is constitutive and occurs in the absence of any DNA-damaging stimulus. Phosphorylation on Ser-115 is necessary for its nuclear retention. Belongs to the MRNIP family. Extended N-terminus.