Practice question

Pseudouridine, the most abundant RNA modification, is a C5-glycoside isomer of uridine. Normal uridine uses an N1-C1' nitrogen-carbon glycosidic linkage between base and ribose. During pseudouridylation by pseudouridine synthases, the uracil ring rotates, creating a C5-C1' carbon-carbon bond, retaining Watson-Crick face but exposing N1-H as additional hydrogen-bond donor. This C-C linkage increases base stacking, backbone rigidity via water-mediated interactions, thermal stability, and improves translational fidelity in tRNA and rRNA. It occurs post-transcriptionally in nucleolus and is conserved across all domains.