title: Characterization of RNase HII substrate recognition using RNase HII-argonaute chimaeric enzymes from Pyrococcus furiosus.
abstract: RNase H (ribonuclease H) is an endonuclease that cleaves the RNA strand of RNA-DNA duplexes. It has been reported that the three-dimensional structure of RNase H is similar to that of the PIWI domain of the Pyrococcus furiosus Ago (argonaute) protein, although the two enzymes share almost no similarity in their amino acid sequences. Eukaryotic Ago proteins are key components of the RNA-induced silencing complex and are involved in microRNA or siRNA (small interfering RNA) recognition. In contrast, prokaryotic Ago proteins show greater affinity for RNA-DNA hybrids than for RNA-RNA hybrids. Interestingly, we found that wild-type Pf-RNase HII (P. furiosus, RNase HII) digests RNA-RNA duplexes in the presence of Mn2+ ions. To characterize the substrate specificity of Pf-RNase HII, we aligned the amino acid sequences of Pf-RNase HII and Pf-Ago, based on their protein secondary structures. We found that one of the conserved secondary structural regions (the fourth beta-sheet and the fifth alpha-helix of Pf-RNase HII) contains family-specific amino acid residues. Using a series of Pf-RNase HII-Pf-Ago chimaeric mutants of the region, we discovered that residues Asp110, Arg113 and Phe114 are responsible for the dsRNA (double-stranded RNA) digestion activity of Pf-RNase HII. On the basis of the reported three-dimensional structure of Ph-RNase HII from Pyrococcus horikoshii, we built a three-dimensional structural model of RNase HII complexed with its substrate, which suggests that these amino acids are located in the region that discriminates DNA from RNA in the non-substrate strand of the duplexes.
authors.affiliation: Institute for Advanced Biosciences, Keio University, Tsuruoka 997-0017, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Kitamura
authors.forename: Kosuke
authors.initials: K
authors.lastname: Fujishima
authors.forename: Asako
authors.initials: A
authors.lastname: Sato
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tsuchiya
authors.forename: Masaru
authors.initials: M
authors.lastname: Tomita
authors.forename: Akio
authors.initials: A
authors.lastname: Kanai
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001120:Arginine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001224:Aspartic Acid / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002384:Catalysis / Q000187:drug effects; D004591:Electrophoresis, Polyacrylamide Gel; D004722:Endoribonucleases / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008345:Manganese / Q000494:pharmacology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010649:Phenylalanine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020027:Pyrococcus furiosus / Q000201:enzymology* / Q000235:genetics; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016914:Ribonuclease H / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D019843:Archaeal Proteins; D012330:RNA, Double-Stranded; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D001224:Aspartic Acid; D008345:Manganese; D010649:Phenylalanine; D001120:Arginine; D004722:Endoribonucleases; C091139:ribonuclease HII; D016914:Ribonuclease H