Abstract 1927 Pseudouridine Synthase 7 localization influences the mRNA modification landscape and cellular stress tolerance

Pseudouridine (Ψ) is among the most abundant post-transcriptional RNA modifications. Consistent with the broad influence that Ψ exerts on RNA structure and function, the misregulation of Ψ-incorporating enzymes, pseudouridine synthases (PUSs), is associated with a variety of deleterious health outcomes including human-inherited intellectual disorders. PUS enzymes have been studied for decades because of their ability to modify essential non-coding RNAs such as rRNA and tRNA. However, over the last decade it has become apparent that a sub-set of eukaryotic PUS enzymes also target protein coding mRNAs. How these enzymes select their mRNA targets, as well as the ultimate influence of mRNA pseudouridylation on gene expression remains to be determined. There is mounting evidence that factors beyond inherent enzyme preference for particular RNA sequences or substrates strongly influence PUS target selection in cells. Here, we tested how enzyme localization influences which mRNAs are modified by one of the primary mRNA pseudouridinylating enzymes, PUS7. Using Nanopore sequencing we find that the addition of a cytoplasmic localization tag to PUS7 greatly increases the number and variety of pseudouridylated mRNAs. Furthermore, we identify multiple stress conditions (heat shock and oxidative stress) under which PUS7 naturally relocalizes and demonstrates an altered substrate scope. Notably, the localization of PUS7 to the cytoplasm enhances the fitness of cells subject to these same stresses. These data raise the possibility that shifts in PUS7 localization provide cells an avenue to directly alter translation in response to stress.