On the left hand side, Transcription Factor II A (TFIIA) is depicted in purple, shaded darker to represent a protein that joins the complex later on.

Used with permission from the Howard Hughes Medical Institute (www.hhmi.org). All rights reserved.

Related PDB Entry: 1YTF

Experimental Structure Citation

Tan, S., Hunziker, Y., Sargent, D. F., & Richmond, T. J. (1996). Yeast Crystal structure of a yeast TFIIA/TBP/DNA complex. Nature, 381, 127-134.


TFIIA is a general transcription factor that binds directly to the complex, further promoting transcription initiation. TFIIA increases the stability of the already-formed TBP•DNA complex to DNA and bends DNA at a larger angle. TFIIA also increases the surface area of the entire complex, so additional TAFs and coactivators can bind and help initiate transcription.