title: RNase H activity: structure, specificity, and function in reverse transcription.
abstract: This review compares the well-studied RNase H activities of human immunodeficiency virus, type 1 (HIV-1) and Moloney murine leukemia virus (MoMLV) reverse transcriptases. The RNase H domains of HIV-1 and MoMLV are structurally very similar, with functions assigned to conserved subregions like the RNase H primer grip and the connection subdomain, as well as to distinct features like the C-helix and loop in MoMLV RNase H. Like cellular RNases H, catalysis by the retroviral enzymes appears to involve a two-metal ion mechanism. Unlike cellular RNases H, the retroviral RNases H display three different modes of cleavage: internal, DNA 3' end-directed, and RNA 5' end-directed. All three modes of cleavage appear to have roles in reverse transcription. Nucleotide sequence is an important determinant of cleavage specificity with both enzymes exhibiting a preference for specific nucleotides at discrete positions flanking an internal cleavage site as well as during tRNA primer removal and plus-strand primer generation. RNA 5' end-directed and DNA 3' end-directed cleavages show similar sequence preferences at the positions closest to a cleavage site. A model for how RNase H selects cleavage sites is presented that incorporates both sequence preferences and the concept of a defined window for allowable cleavage from a recessed end. Finally, the RNase H activity of HIV-1 is considered as a target for anti-virals as well as a participant in drug resistance.
authors.affiliation: Department of Microbiology, School of Medicine, Box 357242, University of Washington, Seattle, WA 98195, USA.
authors.forename: Sharon J
authors.initials: SJ
authors.lastname: Schultz
authors.forename: James J
authors.initials: JJ
authors.lastname: Champoux
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D018360:Crystallography, X-Ray; D015658:HIV Infections / Q000188:drug therapy / Q000201:enzymology; D015497:HIV-1 / Q000737:chemistry* / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D008979:Moloney murine leukemia virus / Q000737:chemistry* / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012194:RNA-Directed DNA Polymerase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology; D048348:Reverse Transcription / Q000187:drug effects; D016914:Ribonuclease H / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D018894:Reverse Transcriptase Inhibitors; D012194:RNA-Directed DNA Polymerase; D016914:Ribonuclease H