Poster abstracts
Poster number 1 submitted by Rabab Abu Alhasan
Investigating the role of UPF3 factors in assembly and function of premature translation termination complex
Rabab Abu Alhasan (Department of Molecular Genetics), Zhongxia Yi (Department of Molecular Genetics), Sean Myers (Department of Physics), Ralf Bundschuh (Department of Physics), 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 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 core NMD factors UPF1, UPF2, and UPF3. While UPF1 is the main NMD activator of premature termination, the functions of UPF2 and UPF3 in these processes are 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, alongside previous publications, supports the hypothesis that UPF3 factors are involved in the assembly of the prematurely terminating ribosome complex and subsequently in translation termination and ribosome recycling. We find that deletion of both UPF3 paralogs in a human colorectal cancer cell line (HCT116) alters NMD factor association with translating ribosomes. These cells also exhibit decreased ribosomal readthrough which could indicate impaired translation termination and/or ribosome recycling. To further investigate the role of UPF3 factors in the assembly of the premature termination complex and post-termination ribosome dynamics, we are optimizing methods such as total and selective ribosome profiling. These assays, in combination with polysome association and translation termination efficiency assays, will enable a comprehensive investigation of premature termination complex assembly and activity 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
Neu‐Yilik, G., Raimondeau, E., Eliseev, B., Yeramala, L., Amthor, B., Deniaud, A., Huard, K., Kerschgens, K., Hentze, M. W., Schaffitzel, C., & Kulozik, A. E. (2017). Dual function of Upf3b in early and late translation termination. The EMBO Journal, 36(20), 2968–2986.
Keywords: NMD, UPF3, Ribosome TerminationRecycling