Claim: PRPF8, or the pre-mRNA-processing-splicing factor 8, occurs in 2 sequential transesterification steps and the  protein encoded by this gene is a component of both U2- and U12-dependent spliceosomes.
Evidence: Pre-mRNA-processing-splicing factor 8 is a protein that in humans is encoded by the PRPF8 gene. Pre-mRNA splicing occurs in 2 sequential transesterification steps. The protein encoded by this gene is a component of both U2- and U12-dependent spliceosomes, and found to be essential for the catalytic step II in pre-mRNA splicing process.