Catalytic subunit of RNase HII, an endonuclease that specifically degrades the RNA of RNA:DNA hybrids. Participates in DNA replication, possibly by mediating the removal of lagging-strand Okazaki fragment RNA primers during DNA replication. Mediates the excision of single ribonucleotides from DNA:RNA duplexes. Endonucleolytic cleavage to 5'-phosphomonoester. Manganese or magnesium. Binds 1 divalent metal ion per monomer in the absence of substrate. May bind a second metal ion after substrate binding. The RNase 2 complex is a heterotrimer composed of the catalytic subunit RNH201 and of the non-catalytic subunits RNH202 and RNH203. Present with 623 molecules/cell in log phase SD medium. Belongs to the RNase HII family. Eukaryotic subfamily.