MED16 is a conserved Mediator complex subunit that functions as a transcriptional coactivator for RNA polymerase II-dependent genes 1. It serves as a bridge component that facilitates communication between gene-specific regulatory proteins and basal transcription machinery, coordinating enhancer-promoter interactions and preinitiation complex assembly 1. MED16 specifically transduces NRF2-activating signals for antioxidant gene expression through direct association with NRF2 and phosphorylation of RNA polymerase II's C-terminal domain, with approximately 75% of NRF2 target genes showing impaired induction in MED16-deficient cells 2. Recent studies demonstrate that MED16 is required for normal neurodevelopment; biallelic MED16 variants cause autosomal recessive MEDopathy characterized by intellectual disability, speech/motor delay, and multiple congenital anomalies including craniofacial defects, cardiac malformations, and limb anomalies 1. Pathogenic variants lead to nuclear-cytoplasmic mislocalization and loss-of-function effects, with patient-derived iPSCs showing impaired neurite outgrowth and altered neuronal maturation gene transcription 3. Conversely, MED16 downregulation in papillary thyroid cancer promotes tumor progression and radioiodine resistance through TGF-β pathway activation 4. Animal models show MED16 is essential for viability; Med16 knockout mice are preweaning lethal, and med16 loss in Drosophila impairs synaptic transmission 13.