WEHI PhD Completion Seminar hosted by Dr Bernhard Lechtenberg

Sarah Trevelyan

PhD Student – Lechtenberg Laboratory, Ubiquitin division, Healthy Development & Ageing Theme, WEHI

Lost in translation: understanding the RBR E3 ligase RNF14 and its role in a novel ribosomal quality control pathway

Davis Auditorium 

Join via SLIDO enter code #WEHIphdcompletion

Including Q&A session

Followed by refreshments in Tapestry Lounge

Ubiquitination is a post-translational modification with wide ranging effects on protein stability, localisation and interactions. E3 ubiquitin ligases control the final step in the substrate ubiquitination cascade and are therefore critical enzymes in many signalling pathways. One such E3 ligase, RNF14 is a member of the RING-Between-RING (RBR) family of E3s.

RNF14 has emerged as a critical regulator in a novel ribosomal quality control (RQC) pathway. RQC is a crucial cellular mechanism responsible for identifying and resolving faults in protein translation, ensuring high fidelity protein synthesis is preserved. Under specific conditions, ribosomes can stall and collide with others, providing unique molecular cues that a cell must resolve. Here, RNF14 is recruited to stalled ribosomes and ubiquitinates key components including trapped translation factors, leading to their proteasomal degradation. Although RNF14s distinct ubiquitin chain-type signature is known, the architecture of these chains and how they lead to translation factor degradation remains unknown.

During my PhD, I’ve used a combination of in vitro and cell-based assays, and mass spectrometry to show that upon inducing ribosomal stalling by specific drugs, RNF14 generates unconventional, branched ubiquitin chains in vitro and on an endogenous translation factor in cells. To further understand the mechanism of branched chain assembly, I solved a crystal structure of the RNF14 catalytic domain caught in the act of forming a branched ubiquitin chain product. This is the first structure demonstrating how one individual E3 ubiquitin ligase can form branched ubiquitin chains. Overall, this work provides a system and the tools to expand our understanding of ubiquitin branching and why this unique modification is important in RQC and protein degradation.

All welcome!