Initiation of transcription by RNA polymerase II requires
the activities of more than 70 polypeptides. The protein that
coordinates these activities is transcription factor IID (TFIID),
which binds to the core promoter to position the polymerase
properly, serves as the scaffold for assembly of the remainder of
the transcription complex, and acts as a channel for regulatory
signals. TFIID is composed of the TATA-binding protein (TBP) and a
group of evolutionarily conserved proteins known as TBP-associated
factors or TAFs. TAFs may participate in basal transcription, serve
as coactivators, function in promoter recognition or modify general
transcription factors (GTFs) to facilitate complex assembly and
transcription initiation. This gene encodes one of the small
subunits of TFIID that is associated with a subset of TFIID
complexes. Studies with human and mammalian cells have shown that
this subunit is required for transcriptional activation by the
estrogen receptor, for progression through the cell cycle, and may
also be required for certain cellular differentiation programs.
