title: A potential protein-RNA recognition event along the RISC-loading pathway from the structure of A. aeolicus Argonaute with externally bound siRNA.
abstract: Argonaute proteins are key components of the RNA-induced silencing complex (RISC). They provide both architectural and catalytic functionalities associated with small interfering RNA (siRNA) guide strand recognition and subsequent guide strand-mediated cleavage of complementary mRNAs. We report on the 3.0 A crystal structures of 22-mer and 26-mer siRNAs bound to Aquifex aeolicus Argonaute (Aa-Ago), where one 2 nt 3' overhang of the siRNA inserts into a cavity positioned on the outer surface of the PAZ-containing lobe of the bilobal Aa-Ago architecture. The first overhang nucleotide stacks over a tyrosine ring, while the second overhang nucleotide, together with the intervening sugar-phosphate backbone, inserts into a preformed surface cavity. Photochemical crosslinking studies on Aa-Ago with 5-iodoU-labeled single-stranded siRNA and siRNA duplex provide support for this externally bound siRNA-Aa-Ago complex. The structure and biochemical data together provide insights into a protein-RNA recognition event potentially associated with the RISC-loading pathway.
authors.affiliation: Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA.
authors.forename: Yu-Ren
authors.initials: YR
authors.lastname: Yuan
authors.forename: Yi
authors.initials: Y
authors.lastname: Pei
authors.forename: Hong-Ying
authors.initials: HY
authors.lastname: Chen
authors.forename: Thomas
authors.initials: T
authors.lastname: Tuschl
authors.forename: Dinshaw J
authors.initials: DJ
authors.lastname: Patel
mesh_terms: D001665:Binding Sites; D004722:Endoribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D009690:Nucleic Acid Conformation; D034622:RNA Interference; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000737:chemistry* / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D012330:RNA, Double-Stranded; D034741:RNA, Small Interfering; D004722:Endoribonucleases; C504752:argonaute protein, Aquiflex aeolicus