Poster abstracts

Poster number 38 submitted by Lauren Woodward

EJC protein composition and position on mRNAs are influenced by translation

Lauren Woodward (Molecular Genetics, The Ohio State University), Justin Mabin, Robert Patton (Physics, The Ohio State University), Ralf Bundschuh (Physics, The Ohio State University), Guramrit Singh (Molecular Genetics, The Ohio State University)

Abstract:
The Exon Junction Complex (EJC) is comprised of a trimeric core (EIF4AIII, RBM8A, and MAGOH) which is deposited on RNA during splicing 24nt upstream of exon boundaries. The EJC serves as a molecular memory of the splicing reaction and couples diverse post-transcriptional processes by serving as a binding platform for peripherally interacting proteins. Recently, we demonstrated that EJC’s exist in two mutually exclusive biochemical varieties with respect to their peripheral proteins: either bound to CASC3 or RNPS1(Mabin et al., 2018). RNPS1 binds more to EJCs in the nucleus. In contrast, CASC3-bound EJCs represent a later, primarily cytoplasmic EJC composition and display greater sensitivity to the translational status of mRNA. Current models state that EJCs are removed from mRNA co-translationally through the action of the ribosome-associated EJC disassembly factor, PYM. However, translation results in more EJC footprints in the 3’UTR compared to conditions where translation is inhibited. Additionally, EJC binding in the 3’UTR correlates with the number of upstream introns. Thus, EJC footprints in the 3’ may represent EJCs originally deposited at upstream splicing events. This translation-dependent relocation is also evident in EJCs that do not interact with PYM. Taken together, these results suggest translating ribosomes can relocate EJCs downstream of the canonical (-24nt) position independent of PYM-EJC interaction. Future experiments will elucidate the roles of the ribosome of PYM in EJC disassembly.

References:

Mabin, J.W., Woodward, L.A., Patton, R., Yi, Z., Jia, M., Wysocki, V., Bundschuh, R., and Singh, G. (2018). The exon junction complex undergoes a compositional switch that alters mRNP structure and nonsense-mediated mRNA decay activity. BioRxiv.

Keywords: EJC, PYM, EJC disassembly