Poster abstracts

Poster number 46 submitted by Bayley Carter

Investigating PYM1 function in cellular and flaviviral gene expression

Bayley Carter (Department of Molecular Genetics and Center for RNA Biology, OSU), Manu Sanjeev (Department of Molecular Genetics and Center for RNA Biology, OSU), Lauren Wooodward (Department of Molecular Genetics and Center for RNA Biology, OSU), Robert Patton, Sean Myers (Department of Physics, OSU), Ralf Bundschuh (Department of Physics, OSU and Department of Chemistry and Biochemistry, Division of Hematology), Guramrit Singh (Department of Molecular Genetics and Center for RNA Biology, OSU)

Post-transcriptional regulation of RNAs in the cell is critical to proper expression of the genome. The Exon Junction Complex (EJC) is an RNA binding protein complex that has important role in post-transcriptional regulation of RNAs. An EJC is deposited on an mRNA by the spliceosome ~24 nucleotides upstream of exon-exon junctions (canonical position) to serve as an architectural marker of intron positions. Presence of an EJC on mRNA can enhance its export and its translation. Further, presence of an EJC after a stop codon can mark an mRNA for degradation through a process called nonsense mediated decay (NMD). NMD is an essential pathway in eukaryotic cells that degrades premature termination codon (PTC)-containing mRNAs and also regulates expression of many normal mRNAs. Our unpublished work suggests that PYM1, a ribosome associated protein, may regulate EJC binding at positions away from exon-exon junctions (non-canonical). Loss of EJC-PYM1 interaction leads to a decrease of EJC deposition at -24 nucleotide canonical EJC sites and increased EJC deposition away from exon junctions at non-canonical sites on spliced mRNAs and lncRNAs. Upon loss of PYM1-EJC interaction, non-canonical EJC binding is also greatly increased on intronless RNAs, which do not normally have bound EJCs. This has potential implications for the understanding of gene expression of flaviviruses (e.g., Zika virus, West Nile virus), as PYM1 is reported to interact with flavivirial capsid proteins. This interaction may sequester PYM1 away from its role in regulating non-canonical EJCs, leading to EJC assembly on the intronless flaviviral RNAs and thereby influencing their translation and/or NMD. In this work, we are investigating the molecular basis of PYM1-flaviral capsid protein interaction, the effects of PYM1 depletion on nuclear functions of the EJC, as well as the potential translational effects of non-canonical EJC deposition on intronless RNAs. The proposed study will help us understand the role of the EJC in post-transcriptional regulation of RNAs and provide insights into the mechanism of flaviviral infection.

1. Bono, et al. (2004), “Molecular Insights into the Interaction of PYM with Magoh-Y14 Core of the Exon Junction Complex”, EMBO Reports, vol. 5, No. 3, pp.304-310.
2. Gehring, et al. (2009), “Disassembly of the Exon Junction Complexes by PYM”, Cell 137, pp.536-548.
3. Minghua, et al. (2019), “Identification of antiviral roles for the exon–junction complex and nonsensemediated decay in flaviviral infection”, Nature Microbiology 4, pp.985–995.
4. Tan, et al. (2020), “Capsid protein structure in Zika virus reveals the flavivirus assembly process”. Nature Commun 11, 895.

Keywords: Exon Junction Complex , PYM1, Flavivirus