The TFIIA-TAF11 interaction in RNA polymerase II transcription

Abstract

In eukaryotes, RNA polymerase II transcription is a highly regulated process that requires the cooperative interaction of multiple proteins and protein complexes. Transcription is predominantly regulated at the initiation where a large complement of proteins must assemble to form a preinitiation complex (PIC), comprised of RNA polymerase II and general transcription factors, TFIIA, TFIIB, TFIID, TFIIE, TFIIF, and TFIIH. TFIID is required to nucleate the assembly of the PIC and its association to promoters is the rate-limiting step for initiation. TFIID is a multiprotein complex comprised of the TATA binding protein (TBP) and 14 TBP associated factors (TAFs). Both TBP and TAFs make significant contributions to TFIID association with promoters. TBP binds via sequence specific contacts with the TATA element. TAFs facilitate the TFIID affinity and specificity for core promoters through specific interactions with promoter sequences and other components of the transcription machinery. The general transcription factor TFIIA influences TFIID association with promoters through associations with TBP and TAF11. The importance of TFIIA interaction with TBP for transcription has been demonstrated by numerous studies, but TFIIA interaction with TAF11 has not been well defined. To examine the functional significance of the TFIIA-TAF11 interaction, we employed biochemical and genetic analyses to refine the intramolecular contacts between these proteins, and to identify the mechanistic requirements for their association. Our studies determined that interaction with TFIIA requires two distinct regions of TAF11. The structurally conserved histone fold domain (HFD) can mediate interaction with both TFIIA and TAF13. In addition to this region, the Nterminal region of TAF11 is also required for interaction with TFIIA. In vitro studies determine that association between TAF11 and TFIIA is important for interactions at the core promoter. TAF11 imparts changes to TFIIA and TBP interactions with DNA, leading to stimulation of overall complex formation. Moreover, TFIIA-TAF11 interactions at weak or non-consensus TATA elements can be stabilized by TAF11. Finally, our studies demonstrate that TAF11 interaction with TFIIA facilitates core promoter functions that are important for RNA polymerase II transcription. Taken together, the work presented provides a solid foundation for advancing our understanding of RNA polymerase II regulation, with a particular emphasis on the interaction between TFIIA and TAF11 and provides further insights into the functional requirement for this interaction in vivo.