Endonuclease that probably plays a role in the DNA damage response and DNA repair. Interacts (via LEM domain) with BANF1; the interaction may favor BANF1 dimerization. At the steady state, localizes predominantly in the cytoplasm. Expression is predominant in adult bone marrow. Expressed in fetal spleen, liver and thymus. The LEM domain is required for GIY-YIG domain-mediated DNA cleavage and induction of DNA damage response. Truncated N-terminus.