<p>Whereas bacterial and archaeal RNases H2 are active as single polypeptides, the <taxon tax_id="4932">Saccharomyces cerevisiae</taxon> (Baker's yeast) homologue, Rnh2Ap, when expressed in <taxon tax_id="562">Escherichia coli</taxon>, fails to produce an active RNase H2. For RNase H2 activity three proteins are required [Rnh2Ap (Rnh201p), Ydr279p (Rnh202p) and Ylr154p (Rnh203p)]. Deletion of any one of the proteins or mutations in the catalytic site in Rnh2A leads to loss of RNase H2 activity [<cite idref="PUB00044465"/>]. RNase H2 is an endonuclease that specifically degrades the RNA of RNA:DNA hybrids. It participates in DNA replication, possibly by mediating the removal of lagging-strand Okazaki fragment RNA primers during DNA replication. </p><p>This entry represents the catalytic chain of RNase H2, which is found as a single polypeptide in prokaryotes and is part of a three protein complex in eukaryotes. In <taxon tax_id="4932">Saccharomyces cerevisiae</taxon> (Baker's yeast) it is represented by <db_xref db="SWISSPROT" dbkey="P53942"/>. </p> Ribonuclease H2, subunit A