NSUN2 is an RNA cytosine C(5)-methyltransferase that catalyzes 5-methylcytosine (m5C) formation across diverse RNA substrates including tRNAs, mRNAs, and long non-coding RNAs 123. The enzyme methylates specific tRNA positions (34, 48-50) to promote tRNA stability and generate tRNA-derived fragments 3, while also mediating mitochondrial tRNA methylation 4. In mRNAs, NSUN2-catalyzed m5C modifications stabilize transcripts through recognition by the m5C reader YBX1, preventing mRNA decay 56. NSUN2 additionally regulates mRNA nuclear export via ALYREF-mediated recognition of methylated transcripts 7 and facilitates vault RNA processing into regulatory small RNAs 8. NSUN2 plays critical roles in development, supporting epidermal stem cell differentiation, testis differentiation, and maternal-zygotic transition by enhancing protein synthesis 3. Beyond its methyltransferase function, NSUN2 is required for proper spindle assembly and chromosome 5 9. Clinically, NSUN2 dysregulation drives multiple cancer types. It acts as a glucose sensor promoting tumorigenesis and immunotherapy resistance via TREX2 stabilization and cGAS/STING suppression 10. NSUN2 overexpression mediates intrinsic EGFR-TKI resistance in lung cancer through QSOX1 m5C modification 11, promotes esophageal squamous cell carcinoma progression via SMOX stabilization 12, and enhances colorectal cancer through SKIL and ENO1 m5C-dependent regulation 1314. Additionally, lactate-mediated NSUN2 lactylation drives ferroptosis resistance in gastric and endometrial cancers 1516, implicating NSUN2 as a promising therapeutic target.