Ubiquitination is a post-translational modification fundamental to nearly all aspects of eukaryotic biology. Initially established as a degradative signal, distinct ubiquitin chains are now well recognised to have critical non-degradative functions within signalling pathways including roles in protein stability, activity, localisation, and protein-protein interactions. E3 ligases catalyse the final step in the ubiquitination cascade, working sequentially with E1 activating and E2 conjugating enzymes. Members of the RBR (RING-Between-RING) E3 ligase family act as important regulators in many physiological processes wherein irregular activity has been linked to diseases including Parkinson’s disease, inflammation, and cancer.
One RBR family member, RNF14, is one of only two human RBRs conserved in yeast, suggesting a critical biological function. Physiologically, RNF14 is a co-activator of both androgen receptor (AR)-controlled and TCF/ß-catenin-controlled transcription. Aberrant RNF14 function has been linked to the malignancy of several cancers, including prostate and colon cancer. Additionally, RNF14 promotes the activation of hyperactive AR and ß-catenin mutants in cancer cell lines, indicating a possibility for therapeutic intervention. Currently, little is known about the molecular role of RNF14 in the above gene regulatory pathways, including substrate identification, and the downstream effects of substrate ubiquitination.
My work to date has shown that RNF14 catalytic activity is regulated by autoinhibition via its N-terminal RWD domain and that RNF14 forms non-canonical lysine-6 (K6) polyubiquitin chains. The cellular function of such ubiquitin chains remains largely understudied and my insights present an opportunity to investigate the role of this signalling mark within the context of transcriptional regulation. By using a combination of X-ray crystallography, biochemical activity assays, mass spectrometry and interact-omic techniques such as BioID, this project will lay the foundation to better understand the molecular and biological functions of RNF14 and its role in human disease while establishing its potential as a drug target.