title: A labile phosphodiester bond at the ligation junction in a circular intervening sequence RNA.
abstract: The excised intervening sequence of the Tetrahymena ribosomal RNA precursor mediates its own covalent cyclization in the absence of any protein. The circular molecule undergoes slow reopening at a single phosphodiester bond, the one that was formed during cyclization. The resulting linear molecule has 5'-phosphate and 3'-hydroxyl termini; these are unusual products for RNA hydrolysis but are typical of the other reactions mediated by this molecule. The reopened circle retains cleavage-ligation activity, as evidenced by its ability to undergo another round of cyclization and reopening. The finding that an RNA molecule can be folded so that a specific phosphate can be strained or activated helps to explain how the activation energy is lowered for RNA self-splicing. The proposed mechanisms may be relevant to several other RNA cleavage reactions that are RNA-mediated.
mesh_terms: D000818:Animals; D001483:Base Sequence; D003500:Cyclization; D004591:Electrophoresis, Polyacrylamide Gel; D012313:RNA / Q000378:metabolism*; D012326:RNA Splicing; D000079962:RNA, Circular; D012335:RNA, Ribosomal / Q000378:metabolism; D013768:Tetrahymena / Q000235:genetics; D014981:Xenopus
chemical_list: D000079962:RNA, Circular; D012335:RNA, Ribosomal; D012313:RNA