Structure of a TFIIB-TBP-TATA-element and its Assembly
by Jolee J. Passanante
Eukaryotic transcription, while sharing similarities with the analogous process in Prokaryotes, is notably more complex and as a result is less well characterized. Out of all eukaryotic transcription the best understood at the molecular level is for genes which are transcribed by RNA pol II. This process proceeds through the recognition of the TATA box region of the promoter by TFIID with the help of TBP. This forms the pre-initiation complex (PIC). TFIIB then enters the complex creating heterotrimeric protein/DNA structure that can then be recognized by a pol II complex.
The paper in review has solved the crystal structure (2.7 A res) of human-TFIIB bound to TBP2 from Arabidopsis, which is in turn selectively binding to the adenovirus Major Late Promoter (AdMLP). Although in vivo the PIC begins with the TBP mediated positioning of TFIID in vitro studies show that it is possible to initiate transcription with only the TBP-TFIIB complex. This indicates that TBP and TFIIB can position Pol II alone. It is this TBP-TFIIB Pol II positioning complex which has been imaged here.
Assembly of the Complex: