UBE2D3 is a ubiquitin-conjugating enzyme that catalyzes the covalent attachment of ubiquitin to target proteins, functioning as a key component of the ubiquitin-proteasome system 123. It catalyzes both Lys-11- and Lys-48-linked polyubiquitination, acting as an initiator E2 with partners including E3 ligases FBXW11, RNF8, BRCA1/BARD1, CBL, and STUB1 to regulate diverse cellular processes 145. UBE2D3 participates in critical cellular functions including NF-κB pathway regulation through NFKBIA degradation, DNA damage response and repair, and PCNA-mediated DNA damage tolerance 456. Clinically, UBE2D3 has emerged as a significant cancer-relevant protein with context-dependent roles. In esophageal carcinoma, UBE2D3 overexpression increases radiosensitivity by promoting hTERT degradation, whereas downregulation confers radioresistance 78. Conversely, in pancreatic cancer, IFN-γ-driven UBE2D3 upregulation impairs antigen presentation by mediating K63-linked polyubiquitination of TAP2, enabling tumor immune evasion, making it a therapeutic target for enhancing anti-tumor immunity 9. Additionally, UBE2D3 orchestrates ATM signaling in DNA damage responses 6 and contributes to NF-κB-mediated inflammation in glioblastoma and colon cancer 1011, suggesting multi-faceted roles in tumorigenesis dependent on tissue and microenvironmental context.