RNA structure, not sequence, determines the 5' splice-site specificity of a group I intron.
The group I self-splicing introns act at exon-intron junctions without recognizing a particular sequence. In order to understand splice-site selection, we have developed an assay system based on the Tetrahymena ribozyme to allow the study of numerous 5'-splice-site variants. Cleavage at the correct site requires formation of the correct secondary structure and occurs most efficiently within a 3-base-pair window centered on base pair 5 from the bottom of the P1 stem. Within this window the ribozyme recognizes and cleaves at a "wobble" base pair; the base pair above the cleavage site also influences splicing efficiency. The recognition of RNA structure rather than sequence explains the ability of these transposable introns to splice out of a variety of sequence contexts.
Doudna
J A
JA
Department of Molecular Biology, Massachusetts General Hospital, Boston 02114.
Cormack
B P
BP
Szostak
J W
JW
D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D005091:Exons; D007438:Introns; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D010957:Plasmids; D012326:RNA Splicing; D016337:RNA, Catalytic; D012335:RNA, Ribosomal / Q000235:genetics*; D013768:Tetrahymena / Q000235:genetics*
D016337:RNA, Catalytic; D012335:RNA, Ribosomal