Self-splicing of the Tetrahymena pre-rRNA is
inhibited by a conserved rRNA hairpin P(−1) upstream
of the 5′ splice site. P(−1) inhibits self-splicing
by competing with formation of the P1 splice site helix.
Here we show that the P(−1) hairpin also enhances
dissociation of the spliced products, which was monitored
by native gel electrophoresis. Mutations that stabilize
the rRNA hairpin increase the rate of dissociation approximately
10-fold, from 0.5 min−1 for the wild-type
RNA to ∼4 min−1 at 30 °C. Conversely,
mutations or oligonucleotides that inhibit refolding of
the exons and that stabilize the P1 helix decrease the rate
of product release. The results suggest that refolding of
products can be used to stimulate the turnover of ribozyme-catalyzed
reactions. In the pre-rRNA, this conformational change
helps shift the equilibrium of self-splicing toward the
mature rRNA.