Accurate transcription <i>in vivo</i> requires at least six general transcription initiation factors, in addition to RNA polymerase II. Transcription initiation factor IIF (TFIIF) is a tetramer of two beta subunits associate with two alpha subunits which interacts directly with RNA polymerase II. The beta subunit of TFIIF is required for recruitment of RNA polymerase II onto the promoter.