The fundamental transcription factor TFIIA stabilizes the DNA binding of TATA box-binding protein (TBP). It also plays a very important role in the activation of fundamental transcription factor TFIID by the function of the transcription regulator factor. The budding yeast TFIIA is composed of two subunits, Toa1p (286aa) and Toa2p (122aa). The product is prepared by immunizing rabbit with recombinant protein which was over-expressed in E. coli with a plasmid carrying the entire Toa1p protein (1-286aa) of budding yeast, and purified by chromatography.