rnhA is an endonuclease that specifically degrades the RNA of RNA-DNA hybrids. Localized to the nucleus, this protein mediates the removal of Okazaki fragment RNA primers that are present on the lagging strand during DNA replication. rnhA catalyzes the endonucleolytic cleavage of RNA to a 5'-phosphomonoester and is able to bind magnesium or manganese as cofactors.