Kinase activity and phosphorylation of the largest subunit of TFIIF transcription factor

The largest subunit of the human basal transcription factor TFIIF alpha (al so called RAP74) was reported previously to be the target of some phospho/d ephosphorylation process. We show that TFIIF alpha possesses a serine/threo nine kinase activity, allowing an autophosphorylation of the two residues a t position serine 385 and threonine 389. Mutation analysis strongly suggest s that autophosphorylation of both sites regulates the transcription elonga tion process. Moreover we also evidence three additional phosphorylation si tes located at positions 207-230, 271-283, and 335-344. These sites are pho sphorylated by casein kinase II-like kinases and TAF(II)250, a component of TFIID.