Pseudouridylation landscape across 42 nuclear-encoded S. cerevisiae tRNAs

Pseudouridine is the most abundant RNA base modification due to its prevalence in tRNA and rRNA, where it serves as a key modulator of structure and function. Yet, in the widely used model organism, the budding yeast Saccharomyces cerevisiae , tRNA pseudouridine sites have not been comprehensively annotated. Here, we performed two high-throughput methods established for detecting tRNA pseudouridylation positions: Nanopore direct RNA sequencing (DRS) and 2-bromoacrylamide-assisted cyclization sequencing (BACS). Using DRS, we sequenced cytosolic tRNA from seven pseudouridine synthase (PUS) knockout S. cerevisiae strains , including deletion strains of Pus1, Pus3, and Pus7. Analysis of these data verified thirty-two existing pseudouridine annotations and predicted an additional ten previously unannotated pseudouridine sites. Our analysis also revealed DRS signal changes at several non-uridine sites with the loss of a PUS, including apparent changes in modification abundances at position 37 upon deletion of Pus3. Liquid chromatography tandem mass spectrometry (LC-MS/MS) and primer extension assays, however, indicated no change in the abundance of these modifications with the loss of Pus3, underscoring the need for caution in interpreting DRS-based signal changes. Using BACS, we confirmed the ten DRS-predicted novel sites, while further detecting eleven additional previously unannotated pseudouridine sites. Combining existing modification annotations from the Modomics database with our DRS and BACS datasets, we created a map of all detected pseudouridines—totaling 126 sites, including 21 novel sites—and the enzymes responsible for their catalysis, across the forty-two nuclear-encoded S. cerevisiae tRNA isoacceptors.