mRNA splicing efficiency in yeast and the contribution of nonconserved sequences.

A simple kinetic model for mRNA splicing predicts the way in which in vivo steady state precursor RNA levels (P) and messenger RNA levels (M) vary as a function of the rate constant of the splicing reaction (ksp). The model points to M/P as the best measure of ksp. The analysis of a set of intron mutations in a yeast gene supports the general features of the model and shows that the splicing efficiency of transcripts containing the wild-type intron is well in excess of what is necessary to generate normal mRNA levels. The data also suggest that regions of the intron, in addition to the well-conserved consensus sequences, contribute to efficient splicing.