USP8 deubiquitylation-boosted NSUN4 potentiates lung squamous cell carcinoma progression by m5C methylation of DHCR24

RNA methylation is widely present in various physiological and pathological processes. However, little is known about 5-methylcytosine (m5C) modifications. In this study, we provide an overview of the biological roles of RNA methyltransferase NOP2/Sun 4 (NSUN4) in lung squamous cell carcinoma (LUSC). Our results confirm that overexpression of NSUN4 has oncogenic effects. Mechanistic studies reveal that ubiquitin-specific peptidase 8 (USP8) stabilizes NSUN4 by inhibiting its specific K11-linked polyubiquitination. Consequently, we perform high-throughput RNA bisulfite sequencing after NSUN4 knockdown. Our sequencing results identify numerous m5C sites of oncogenes that are causally related to their regulation in LUSC. Mechanistically, NSUN4 and Y-box binding protein 1(YBX1) are shown to drive LUSC pathogenesis by targeting m5C methylation sites in the 3' untranslated region of DHCR24. Clinically, high expression of NSUN4 and DHCR24 is associated with poorer patient survival. Our findings reveal the mechanism by which RNA-m5C regulates oncogene activation, providing a potential therapeutic strategy for LUSC.