title: RNA aptamers that bind to and inhibit the ribosome-inactivating protein, pepocin.
abstract: Pepocin, isolated from Cucurbita pepo, is a ribosome-inactivating protein (RIP). RIPs site-specifically recognize and depurinate an adenosine at position 4324 in rat 28 S rRNA, rendering the ribosome incapable of interacting with essential elongation factors. Aptamers that target pepocin were isolated from a degenerate RNA pool by in vitro selection. A conserved hairpin motif, quite different from the sequence of the toxin-substrate domain in rat 28 S rRNA, was identified in the aptamer sequences. The aptamers selectively bind to pepocin with dissociation constants between 20 and 30 nM and inhibit the N-glycosidase activity of pepocin on rat liver 28 S rRNA. Competitive binding experiments using aptamer variants suggest that the conserved hairpin region in the anti-pepocin aptamer binds near the catalytic site on pepocin and prevents the interaction of pepocin and 28 S rRNA. Anti-RIP aptamers have potential use in diagnostic systems for the detection of pepocin or could be used as therapy to prevent the action of pepocin in mammalian cells.
authors.affiliation: Yokoyama CytoLogic Project, ERATO, JST, c/o RIKEN, Hirosawa, Wako-shi, Saitama 351-0198, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Hirao
authors.forename: K
authors.initials: K
authors.lastname: Madin
authors.forename: Y
authors.initials: Y
authors.lastname: Endo
authors.forename: S
authors.initials: S
authors.lastname: Yokoyama
authors.forename: A D
authors.initials: AD
authors.lastname: Ellington
mesh_terms: D000818:Animals; D001483:Base Sequence; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010940:Plant Proteins / Q000378:metabolism*; D011485:Protein Binding; D012313:RNA / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D054789:Ribosome Inactivating Proteins, Type 1; D012689:Sequence Homology, Nucleic Acid
chemical_list: D010940:Plant Proteins; D054789:Ribosome Inactivating Proteins, Type 1; C113092:pepocin protein, Cucurbita pepo; D012313:RNA