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Paper Chase

RNA structure, not sequence, determines the 5' splice-site specificity of a group I intron.

Proc. Natl. Acad. Sci. U.S.A.. 10 1, 1989;86(19):7402-6.
Doudna JA, Cormack BP, Szostak JW.

Department of Molecular Biology, Massachusetts General Hospital, Boston 02114.


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.