Binding activity of the human transcription factor TFIID

In order to investigate the conformational state of the human TFIID, we studied the structure of the TATA-box binding protein (TBP) which is the DNA-binding subunit of the transcription factor TFIID required for transcriptional initiation by RNA polymerase II. We showed that TBP was able to form dimers and tetramers by chemical crosslinking, subunit exchange, ultracentrifugation and gel shift experiment. These findings indicate that the TBP homodimers could be the inactive binding form of TFIID and therefore could explain the lack of Gal4-activated transcriptional activity of the E. coli-expressed human TBP.