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.Drane P., Oncogene 15:3013-3024(1997).Yuan C.-X., Proc. Natl. Acad. Sci. U.S.A. 95:7939-7944(1998).Naeaer A.M., Nature 398:828-832(1999).