title: Novel splicing mechanism for the ribosomal RNA intron in the archaebacterium Desulfurococcus mobilis.
abstract: The intron of the 23S rRNA gene of D. mobilis is excised from the pre-23S RNA at specific sites in vivo and subsequently ligated to form a stable circular RNA, with a normal 5'-3' phosphodiester bond, containing the entire intron sequence; 95% of this RNA codes for a protein of 194 amino acids that can be expressed in E. coli. Crude cell extracts from D. mobilis also induce a two-step slicing reaction in vitro, producing the same circular intron RNA but a low yield of ligated exons. Cleavage depends on the RNA structure adjacent to the cleavage site and yields a 3'-terminal phosphate. Splicing is enhanced by GTP, but does not require divalent metal ions. The cleavage and exon-splicing reactions resemble those found for tRNA introns in eukaryotes and a possible structural rationale for this similarity is considered together with its possible implications for the origin of eukaryotic rRNA and tRNA introns.
mesh_terms: D000595:Amino Acid Sequence; D001105:Archaea / Q000235:genetics*; D001419:Bacteria / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D004275:DNA, Ribosomal / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D007438:Introns; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012326:RNA Splicing; D012335:RNA, Ribosomal / Q000235:genetics*; D012338:RNA, Ribosomal, 23S / Q000235:genetics*
chemical_list: D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D012338:RNA, Ribosomal, 23S