Structural and Dynamic Regulation of TFIID-Mediated Transcription Initiation Complex Assembly by the Tumor Suppressor P53 Protein

Abstract

p53 plays a central role in tumor suppression. To quickly respond to diverse stress stimuli, p53 binds specific elements in various target promoters to induce vast gene networks for maintaining cellular integrity. p53 stimulates transcription in part by aiding promoter recruitment of the transcription machinery. TFIID, a key component within the transcription machinery, is responsible for binding specific core promoter DNA sequences and recruiting other basal factors including RNA Polymerase II to initiate transcription. However, the exact mechanism underlying how p53 facilitates TFIID-mediated transcription is unclear.Each p53 target gene has a unique arrangement of p53-responsive and core promoter elements. How these various arrangements on different gene promoters regulate the structural architecture of TFIID and the positioning of p53/specific elements remains unknown. Moreover, structural information of p53 bound to its various target promoters and other factors remains elusive. Therefore, we aim to decipher the molecular mechanism underlying p53's ability to stimulate transcription by revealing the biochemical, structural and dynamic basis of TFIID bound to p53 and promoter DNA.To this end, we established unique protein purification strategies to generate high-purity native TFIID complex bound to p53/TFIIA/native promoter DNA. We next determined the 3D structures of TFIID/p53/TFIIA co-complexes on two distinct p53 target gene promoters via single particle cryo-electron microscopy. Strikingly, we discovered a common mode of TFIID binding to different types of promoters. Our biochemical studies showed that p53 significantly promotes TFIID's interaction with DNA. To further mechanistically dissect TFIID's enhanced promoter recognition/binding directed by p53, we examined the dynamic interaction between p53, TFIID and promoter DNA via single molecule TIRF microscopy. Taken together, our structural and functional studies elucidate how p53 facilitates TFIID-mediated transcription initiation complex assembly on different p53 target gene promoters.