GTF2B, also known as transcription factor II B, is one of several general transcription factors that make up the RNA polymerase II preinitiation complex. It localizes to the nucleus where it forms a complex (the DAB complex) with transcription factors IID and IIA. The protein serves as a bridge between IID, the factor which initially recognizes the promoter sequence, and RNA polymerase II. It is involved in the selection of the transcription start site. Recombinant GTF2B protein was expressed in E. coli and purified by using conventional chromatography techniques.