The family is divided into evolutionarily related groups with slightly different substrate preferences, broadly designated ribonuclease H1 and H2.[2] The human genome encodes both H1 and H2. Human ribonuclease H2 is a heterotrimeric complex composed of three subunits, mutations in any of which are among the genetic causes of a rare disease known as Aicardi–Goutières syndrome.[3] A third type, closely related to H2, is found only in a few prokaryotes,[4] whereas H1 and H2 occur in all domains of life.[4] Additionally, RNase H1-like retroviral ribonuclease H domains occur in multidomain reverse transcriptase proteins, which are encoded by retroviruses such as HIV and are required for viral replication.[5][6]
In eukaryotes, ribonuclease H1 is involved in DNA replication of the mitochondrial genome. Both H1 and H2 are involved in genome maintenance tasks such as processing of R-loop structures.[2][7]
^PDB: 1JL1; Goedken ER, Marqusee S (December 2001). "Native-state energetics of a thermostabilized variant of ribonuclease HI". Journal of Molecular Biology. 314 (4): 863–71. doi:10.1006/jmbi.2001.5184. PMID11734003.
