Dissecting the interplay between transactivation and DNA binding domains of ATF4 transcription factor

Abstract

Despite their involvement in nearly 19% of human diseases, transcription factors (TFs) have historically been labeled "undruggable" due to significant structural disorder, lack of ligand binding sites, and a lack of specificity in their interaction networks. Nonetheless, recent advance in therapeutic approach and research have led to discovering potential molecules targeting not only conventional ligand binding pockets but also disorder regions. Current targeting strategies include disrupting TF binding partner interactions, targeting regulatory domains, and blocking TF-DNA interactions to modulate transcriptional activities. The ultimate objective of this dissertation is to pave a way for developing a new therapeutic strategy targeting the monomeric states of hyperactive transcription factors such as ATF4 for targeted degradation prior to their association with partner proteins and DNA. This proposed novel approach will involves modulating specific intramolecular interactions that regulate transcriptional activities, focusing on the poorly conserved transactivation domain (TAD) and highly conserved DNA binding domain (DBD). This dissertation explores the mechanism of intramolecular interaction between TAD domain and DBD domain of ATF4 bZip transcription factor. The first part of chapter one provides a historical perspective of human transcription factors and current advances in drug targeting, particularly in cancers. The second part of chapter one is a literature review of a bZip transcription factor, ATF4, which transcriptional activities is often deregulated/overactivated in stress-related diseases through cellular response pathway called ISR (integrated stress response). The second chapter is a modified manuscript published in Journal of Biological Chemistry focusing on the structural characteristics of the predominantly disordered TAD domain of ATF4. While it is established that TADs regulate the DNA binding activities of DNA-binding domains (DBDs) in many transcription factors (TFs), our study reveals a novel finding: the modulation can be reciprocal. Specifically, we demonstrate that phosphorylation of the TAD by CKII kinase, which regulates ATF4 cellular activity, occurs only in the presence of intramolecular interactions between the TAD and DBD domains. The third chapter is a preliminary manuscript to be submitted to Journal of Biological Chemistry which explore the details mechanism of such intramolecular interaction and its influence on ATF4 DNA binding activities. Finally, the fourth chapter outline the current progress in paving a way for developing a new therapeutic strategy targeting the monomeric states of hyperactive transcription factors such as ATF4 for targeted degradation prior to their association with partner proteins and DNA. Overall, this dissertation highlights the significance of intramolecular interaction between TAD and DBD of ATF4 transcription factor that regulate not only its DNA binding activity but also cellular stability.