SIAH2 is a RING E3 ubiquitin ligase that mediates ubiquitination and proteasomal degradation of diverse substrate proteins 1. The enzyme functions by accepting ubiquitin from E2 enzymes and transferring it to target substrates either through direct binding or as a component of larger E3 complexes 1. SIAH2 regulates multiple cellular processes including transcription, apoptosis, cell cycle control, and circadian rhythm by targeting substrates such as transcriptional regulators (PML, NCOR1), cell surface receptors (DCC), and circadian repressors (NR1D1, NR1D2) 12. A critical function involves hypoxia regulation, where SIAH2 degrades prolyl hydroxylases PHD1 and PHD3, allowing HIF-1α accumulation under hypoxic conditions 3. SIAH2 exhibits context-dependent roles in cancer, promoting tumorigenesis in prostate, lung, gastric, and liver cancers while suppressing tumor progression in hepatocellular carcinoma through WNK1 degradation 45. Additionally, SIAH2 regulates adipogenesis by targeting the antiadipogenic protein ZFP521 for degradation 6 and controls neuronal differentiation by antagonizing DCC receptor signaling in cerebellar development 7. These diverse functions underscore SIAH2's importance as a regulatory hub in cellular homeostasis and disease pathogenesis.