MED12 is a component of the multisubunit mediator complex that functions as an interface between gene-specific transcription factors and the RNA Pol II/general transcription factor machinery. The mediator complex was first identified as a coactivator of the thyroid hormone receptor and has since been observed to function as a coactivator of a variety of transcription factors. In this context, MED12 interaction with beta-catenin has been shown to be required for Wnt-signaling dependent transcription.