Poster abstracts
Poster number 127 submitted by Savanna Schutte
Exploring the roles of UPF3 functional domains within Nonsense-Mediated mRNA Decay
Savanna P. Schutte (Department of Molecular Genetics, The Ohio State University), Rabab Abu Alhasan (Department of Molecular Genetics, The Ohio State University), Rene M. Arvola (Department of Molecular Genetics, The Ohio State University), Guramrit Singh (Department of Molecular Genetics, Center for RNA Biology, The Ohio State University)
Abstract:
Nonsense-mediated decay (NMD) is a crucial post-transcriptional mechanism that regulates both quality and quantity of eukaryotic mRNAs. This pathway targets mRNAs containing premature termination codons (PTCs) for degradation to prevent the production of C-terminal truncated protein products. NMD also regulates gene expression by targeting a percentage of all endogenous mRNAs where termination is apparently aberrant. Prematurely terminating ribosomes are first recognized by the core NMD factors UPF1, UPF2, and UPF3, and the NMD pathway is activated upon UPF1 phosphorylation. While the paralogous UPF3 factors, UPF3A and UPF3B, are known NMD enhancers, their precise molecular function remains unclear as they are non-essential in the mammalian NMD pathway. Canonical NMD targets bear exon-junction complexes (EJCs) downstream of PTCs which associate with mRNA exon-exon junctions post-splicing. UPF3 has been proposed to enhance NMD by linking the premature termination complex with the EJC. Previous work in our lab, however, has shown that UPF3 still acts as an NMD enhancer without its EJC binding activity. In exploring the other roles of UPF3 in the premature termination complex, we found that the knockout of UPF3B in a human colorectal cancer cell line (HCT116) increases UPF1 and UPF2 association with ribosomal complexes. Our ongoing work suggests that UPF3 has distinct roles in composition and activity of the premature termination complex. Our data supports the hypothesis that UPF3B influences the arrangement of ribosome-associated premature termination complexes likely via its UPF2-binding activity rather than through bridging with the EJC. We also found that disrupting UPF2 binding has little effect on the decay of UPF3B-dependent NMD targets while decay is strongly inhibited when the loss of UPF2 binding is coupled with partial deletion of UPF3B’s mid domain. Thus, functional domains of UPF3B could act semi-redundantly to facilitate NMD enhancement.
References:
Yi, Z., Arvola, R. M., Myers, S., Dilsavor, C. N., Abu Alhasan, R., Carter, B. N., Patton, R. D., Bundschuh, R., & Singh, G. (2022). Mammalian UPF3A and UPF3B can activate nonsense-mediated mRNA decay independently of their exon junction complex binding. The EMBO Journal, e109202
Keywords: nonsense-mediated mRNA decay, UPF3, translation termination