MED30 is a core subunit of the mediator complex head module that functions as a transcriptional coactivator bridging gene-specific regulatory proteins to RNA polymerase II machinery 1. As a component of the mediator complex, MED30 participates in regulated transcription of nearly all RNA polymerase II-dependent genes and assists in preinitiation complex assembly 1. MED30 expression is induced by tumor microenvironment conditions including hypoxia, serum deprivation, and glucose deprivation through HIF1α and p53-dependent mechanisms 1. In glioblastoma, MED30 overexpression promotes cell proliferation while reducing migration and conferring temozolomide sensitivity 1. Similarly, MED30 overexpression in gastric cancer increases proliferation, migration, and invasion, with knockdown inhibiting tumorigenicity in mice 2. However, MED30 shows contrasting roles across cancers: in bladder cancer, higher MED30 expression associates with better patient survival, and MED30 knockdown reduces proliferation and invasion 3. Beyond cancer, MED30 missense mutations cause progressive cardiomyopathy in mice 4, and MED30 participates in endothelial differentiation through alternative splicing 5. MED30 hypermethylation serves as a potential diagnostic biomarker in atrial fibrillation 6, and MED30 is frequently detected in systemic sclerosis immune complexes, potentially affecting endothelial function 7. MED30 knockdown impairs HIV-1 transcription, particularly unspliced viral transcript formation 8.