Mediator of RNA polymerase II transcription subunit 4 also known as mediator complex subunit 4 (MED4) or vitamin D3 receptor-interacting protein complex 36 kDa component (DRIP36) is a protein that in humans is encoded by the MED4 gene.

The Mediator is a multiprotein coactivator that is required by DNA-binding transcription factors for activation of polymerase II (see MIM 180660)-transcribed genes. MED4 appears to be a core Mediator subunit and is found in nearly all Mediator preparations (summary by Sato et al., 2004 [PubMed 15175163]).[supplied by OMIM, Nov 2010]. Publication Note: This RefSeq record includes a subset of the publications that are available for this gene. Please see the Gene record to access additional publications.
Function: Component of the Mediator complex, a coactivator involved in the regulated transcription of nearly all RNA polymerase II-dependent genes. Mediator functions as a bridge to convey information from gene-specific regulatory proteins to the basal RNA polymerase II transcription machinery. Mediator is recruited to promoters by direct interactions with regulatory proteins and serves as a scaffold for the assembly of a functional preinitiation complex with RNA polymerase II and the general transcription factors.