Part of the Rad50/Mre11 complex, which is involved in the early steps of DNA double-strand break (DSB) repair (PubMed:11029422, PubMed:18854158, PubMed:18957200). The complex may facilitate opening of the processed DNA ends to aid in the recruitment of HerA and NurA (PubMed:18957200). Mre11 binds to DSB ends and has both double-stranded 3'-5' exonuclease activity and single-stranded endonuclease activity (PubMed:11029422, PubMed:18854158, PubMed:18957200). Binds 2 manganese ions per subunit. Nuclease activity is regulated by Rad50. Homodimer (PubMed:18854158). Forms a heterotetramer composed of two Mre11 subunits and two Rad50 subunits (PubMed:11371344, PubMed:21441914, PubMed:22102415). Homodimerization facilitates DNA binding (PubMed:18854158). Belongs to the MRE11/RAD32 family. Extended N-terminus.