Poster abstracts
Poster number 1 submitted by Rabab Abu Alhasan
Investigating the role of UPF3 factors in the organization and function of the premature translation termination complex
Rabab Abu Alhasan (Department of Molecular Genetics), Rene Arvola (Department of Molecular Genetics), Guramrit Singh (Department of Molecular Genetics)
Abstract:
The nonsense-mediated decay (NMD) pathway is a surveillance pathway that detects faulty mRNAs with premature termination codons (PTC) and targets them for rapid decay to limit the production of truncated proteins. NMD can also target naturally occurring mRNA to regulate their abundance. NMD target identification requires prematurely terminating ribosomes to be recognized by the core NMD factors UPF1, UPF2, and UPF3. While UPF1 is the main NMD activator and sensor of premature termination in mammals, the functions of UPF3 in these processes is not as well understood. Recent work from our lab suggests that paralogous UPF3 factors, UPF3A and UPF3B, are non-essential but important enhancers of the NMD pathway. Additionally, since NMD is initiated on terminating ribosomes at PTCs, the process is expected to be coupled with translation termination and possibly ribosome recycling. Our preliminary work supports the hypothesis that UPF3 factors are involved in the organization of the prematurely terminating ribosome complex and potentially in translation termination and ribosome recycling. We find that deletion of UPF3B in a human colorectal cancer cell line (HCT116) increases UPF1 and UPF2 association with ribosomes that is likely due to an increase in complex stability making it less transient. Additionally, while endogenous UPF3A levels are not sufficient to rescue this phenotype, its overexpression completely rescues the altered ribosome-UPF1/UPF2 binding. We are leveraging the ribosome association assay to identify the UPF3 activities responsible for this premature termination complex organization and their downstream effects on NMD. In addition, we are optimizing a ribosome profiling-based approach to comprehensively investigate these processes in the presence and absence of UPF3 proteins. Overall, our work will illuminate the role of UPF3 in premature translation termination, and thereby in shaping the human transcriptome.
References:
Yi Z, Arvola RM, Myers S, Dilsavor CN, Abu Alhasan R, Carter BN, et al. Mammalian UPF3A and UPF3B can activate nonsense-mediated mRNA decay independently of their exon junction complex binding. EMBO J. 2022;41: e109202. doi:10.15252/embj.2021109202
Keywords: NMD, UPF3, Ribosome TerminationRecycling