The general transcription factor TFIID is comprised of the TATA-binding protein (TBP) and the TBP-associated factors (TAFs). A majority of TAF subunits contain the same histone-fold motif found in the histone octamer component of chromatin. The functional significance of the histone-fold is unclear, and until recently it was not even known if TAF subunits could associate into an octamer complex like the histone octamer.

Through a combination of biochemical and genetic experiments, we have shown that the yeast scTAF9, 6, 12 and 4 subunits associate specifically via their histone-fold motifs to form an octamer complex. We also find that a similar complex can be reconstituted from the SAGA histoneacetyltransferase complex components of scTAF9, 6, 12 and yAda1. Thus the shared scTAF9, 6 and 12 subunits participate in different histone-fold subcomplexes within the SAGA and TFIID gene regulatory complexes.

Reference:

Selleck, W., Howley, R., Fang, J., Podolny, V., Fried, M.G., Buratowski, S. and Tan, S. (2001) A histone fold TAF octamer within the yeast TFIID transcriptional coactivator, Nature Struct. Biol., 8:695-700. (abstract)