Design and Characterization of Bifunctional Glucocorticoid Ligands Capable of Producing Novel Transcriptional Profiles.

Abstract

The process of transcription underlies the expression of all gene profiles. Normal expression is caused by carefully coordinating the assembly of transcriptional proteins at specific genes, a procedure mediated through transcription factors that bind specific sequences of DNA. The glucocorticoid receptor (GR) is a transcription factor that influences the expression of genes involved in inflammation pathways. Drug-like molecules targeting GR are capable of stimulating GR to bind DNA; however, these molecules are unable to exert complete control over the members of the transcriptional complex recruited by GR. As such, we are limited in our control of GR activity. My dissertation focuses on addressing this with new GR ligands designed to recruit specific transcriptional proteins to produce novel, desired expression profiles. We first conjugated a GR molecule to a ligand of the protein FKBP. This bifunctional ligand was capable of localizing GR to DNA, recruiting FKBP-fusions to the GR-regulated gene, and producing transcriptional activity dictated by the recruitment. This was achieved with the recruitment of both a transcriptionally activating protein and a repressing protein, demonstrating the adaptability of this system to toggle the output of a gene of interest. The design of our system benefits from its inherent modularity; expanding to new targets is simply achieved through synthetic conjugation to an alternative ligand. In a first application of this strategy, we conjugated an agonistic GR ligand to a selective inhibitor of the transcriptional protein BRD4. Recruitment of BRD4 to GR resulted in the suppression of transcription at select genes, and this selectivity drives a novel profile of activated and suppressed genes. In a second application, we conjugated a GR antagonist to the BRD4 inhibitor, allowing forthe further production of novel transcriptional profiles with potential pharmacological utility. This dissertation also includes a study aimed at introducing undergraduate students to the scientific principles of modern chemical biology research. To enhance student learning, we have developed a new guided-inquiry experimental module for biochemistry laboratory courses. This has been well received, and assessment metrics indicate that the incorporation into the University of Michigan’s biochemistry course has raised student cognitive abilities in analysis and application.