TATA-box-binding protein
positive regulation of transcription initiation by RNA polymerase II
Structural insights into preinitiation complex assembly on core promoters.
Transcription factor IID (TFIID) recognizes core promoters and supports preinitiation complex (PIC) assembly for RNA polymerase II (Pol II)-mediated eukaryotic transcription. We determined the structures of human TFIID-based PIC in three stepwise assembly states and revealed two-track PIC assembly: stepwise promoter deposition to Pol II and extensive modular reorganization on track I (on TATA-TFIID-binding element promoters) versus direct promoter deposition on track II (on TATA-only and TATA-less promoters). The two tracks converge at an ~50-subunit holo PIC in identical conformation, whereby TFIID stabilizes PIC organization and supports loading of cyclin-dependent kinase (CDK)-activating kinase (CAK) onto Pol II and CAK-mediated phosphorylation of the Pol II carboxyl-terminal domain. Unexpectedly, TBP of TFIID similarly bends TATA box and TATA-less promoters in PIC. Our study provides structural visualization of stepwise PIC assembly on highly diversified promoters.