PUS7 is a pseudouridine synthase that catalyzes pseudouridylation, the most abundant RNA modification, across diverse RNA substrates including tRNAs, mRNAs, and non-coding RNAs 12. In embryonic stem cells, PUS7 regulates protein synthesis by pseudouridylating tRNA-derived fragments (tRFs) that inhibit translation initiation 2. Additionally, PUS7 modifies mRNAs containing the consensus sequence 5'-UGUAG-3' and mediates co-transcriptional pseudouridylation of pre-mRNAs near splice sites, directly regulating alternative splicing and 3' end processing 3. This epitranscriptomic regulation is critical for normal development, as PUS7 controls hematopoietic and mesoderm development 2. Clinically, PUS7 dysregulation is associated with cancer progression. High PUS7 expression correlates with poor glioblastoma survival, where it supports glioblastoma stem cell tumorigenesis through codon-specific translational control 4. In MYC-driven cancers, PUS7 upregulation promotes adaptive stress responses and amino acid biosynthesis by enhancing ATF4 translation 5. Conversely, tRNA-derived small RNAs can sequester PUS7 to trigger RNA autophagy, providing renoprotection in kidney disease 6. PUS7 dysfunction is also implicated in developmental disorders, including intellectual disability with microcephaly. Chemical inhibitors targeting PUS7 show preclinical therapeutic promise in glioblastoma models 4.