Our results implicate the transition between the first and second catalytic steps as a critical place in the splicing cycle where Prp8-RP mutants influence splicing efficiency.
Notably, U4/U6 unwinding activity is not stimulated by fragments carrying alleles of prp8 that in humans confers an autosomal dominant form of retinitis pigmentosa.
We conclude that the expanded Prp8 Jab1/MPN domain represents a pseudoenzyme converted into a protein-protein interaction platform and that dysfunction of this platform underlies Retinitis pigmentosa.
When stimulated by Prp8, wild type Δ247-Brr2 is able to unwind long stable duplexes in vitro, and even the RP mutants capable of binding RNA with tight affinity are incapable of fully unwinding short duplex RNAs.