These factors work with co-activators to direct transcriptional initiation by the RNA polymerase II apparatus.

The mediator of RNA polymerase II transcription subunit 1 protein is a subunit of the CRSP (cofactor required for SP1 activation) complex, which, along with TFIID, is required for efficient activation by SP1.

This protein is also a component of other multisubunit complexes [e.g., thyroid hormone receptor-(TR-) associated proteins that interact with TR and facilitate TR function on DNA templates in conjunction with initiation factors and cofactors].

[7] MED1 has been shown to interact with: This entry represents subunit Med1 of the Mediator complex.

It is one of three subunits essential for viability of the whole organism via its role in environmentally-directed cell-fate decisions.