Talk abstracts
Talk on Saturday 12:35-12:55pm submitted by Michael Kearse
FMRP inhibits translation elongation independent of RNA G-quadruplexes
MaKenzie R. Scarpitti (Department of Biological Chemistry and Pharmacology, Center for RNA Biology, The Ohio State University, Columbus, OH 43210 USA), Michael G. Kearse (Department of Biological Chemistry and Pharmacology, Center for RNA Biology, The Ohio State University, Columbus, OH 43210 USA)
Abstract:
Loss of expression of fragile X mental retardation protein (FMRP) causes fragile X syndrome, the leading form of inherited intellectual disability and the most common monogenic cause of autism spectrum disorders. FMRP is an RNA-binding protein that controls neuronal mRNA localization and translation. Notably, FMRP is thought to inhibit translation elongation after being recruited to target transcripts via binding RNA G-quadruplexes (G4) within the coding sequence. Here we directly test this model and report that FMRP inhibits translation elongation independent of G4s. Furthermore, we found that the RGG box motif together with its natural C-terminal domain forms a non-canonical RNA-binding domain (ncRBD) that enables FMRP to bind mRNA and all four polymeric RNA sequences. FMRP only inhibits translation when bound to mRNA through this ncRBD. Consistent with stalling elongation and accumulating slowed ribosomes, FMRP inhibited transcripts co-sediment with heavier polysomes compared to transcripts bound by FMRP deleted of the ncRBD. Together, this work shifts our understanding of how FMRP inhibits translation elongation and supports a model where repression is driven by local FMRP and mRNA concentration rather than target mRNA sequence.
Keywords: ribosome, translational control, fragile X