MED7 is a subunit of the Mediator complex, a coactivator essential for RNA polymerase II-dependent transcription. As a component of the Mediator middle module, MED7 functions in bridging gene-specific regulatory proteins to the basal transcription machinery and facilitating preinitiation complex assembly 1. The MED21-MED7 heterodimer hinge is critical for Mediator-RNA polymerase II holoenzyme formation, with mutations impairing Pol II binding affinity 1. MED7 plays important roles in viral transcription; knockdown of MED7 impaired HIV-1 replication by inhibiting early viral transcript formation and Tat-induced transcription 2. In cancer biology, MED7 shows divergent clinical significance. In hepatocellular carcinoma (HCC), MED7 upregulation correlates with advanced stage, poor differentiation, and microvascular invasion, promoting tumorigenesis through multiple gene networks and immune modulation 3. The E2F1 transcription factor transcriptionally activates MED7 in HCC, and inhibiting this E2F1/MED7 axis with baicalein suppresses HCC cell proliferation and invasion 4. Conversely, in breast cancer—particularly ER+ luminal subtypes—high MED7 expression associates with favorable prognostic factors including low grade, smaller tumor size, and improved survival, independently predicting longer breast cancer-specific survival 5. These contrasting cancer associations suggest MED7's context-dependent roles in tumorigenesis.