Pseudouridine synthase that catalyzes pseudouridylation of mRNAs and tRNAs (PubMed:28073919, PubMed:31477916, PubMed:32926445). Mediates pseudouridylation of mRNAs with the consensus sequence 5′-GUUCNANNC-3′, harboring a stem-loop structure (PubMed:28073919, PubMed:31477916). Constitutes the major pseudouridine synthase acting on mRNAs (PubMed:28073919). Also catalyzes pseudouridylation of some tRNAs, including synthesis of pseudouridine(55) from uracil-55, in the psi GC loop of a subset of tRNAs (PubMed:32926445, PubMed:33023933). Promotes the processing of pri-let-7 microRNAs (pri-miRNAs) independently of its RNA pseudouridylate synthase activity (PubMed:32926445). Acts by binding to the stem-loop structure on pri-let-7, preventing LIN28-binding (LIN28A and/or LIN28B), thereby enhancing the interaction between pri-let-7 and the microprocessor DGCR8, which mediates miRNA maturation (PubMed:32926445).
