Description
The transcription factor IIF (TFIIF) is a heterodimer, composed of 58 kDa (RAP74) and 26 kDa (RAP30) subunits. It was first identified through the ability to interact with immobilized RNA Polymerase II. In addition to its role in transcription initiation, TFIIF can increase the specificity and efficiency of RNA Polymerase II transcription, and can especially increase the rate of transcription elongation. Recombinant RAP74 protein is isolated from anE. colistrain that carries the coding sequence of human RAP74, the subunit of TFIIF under the control of T7 promoter. RAP74 is required for stimulation of the rate of RNA Polymerase II elongation through a direct interaction with pol II and for start site selection. RAP74 is heavily phosphorylated in vivo and can be phosphorylated by TAFII250, a subunit of TFIID. Protein is greater than 95% homogeneous and contains no detectable protease, DNase, and RNase activity