Required for transcriptional activation subsequent to the assembly of the preinitiation complex By similarity. 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. Required for transcriptional activation by adenovirus E1A protein. Required for ELK1-dependent transcriptional activation in response to activated Ras signaling.Wiemann S., Genome Res. 11:422-435(2001).Mungall A.J., Nature 425:805-811(2003).Akoulitchev S., Nature 407:102-106(2000).