Phase Separations Driven by RNA Scaffolds and Protein Sequestration in FXTAS

Abstract

Recent evidence indicates that specific RNAs promote formation of ribonucleoprotein condensates by acting as scaffolds for RNA-binding proteins (RBPs).\n\nWe systematically investigated RNA-RBP interaction networks to understand ribonucleoprotein assembly. We found that highly-contacted RNAs are highly structured, have long untranslated regions (UTRs) and contain nucleotide repeat expansions. Among the RNAs with such properties, we identified the FMR1 3 UTR that harbors CGG expansions implicated in Fragile X-associated Tremor/Ataxia Syndrome (FXTAS).\n\nWe studied FMR1 binding partners in silico and in vitro and prioritized the splicing regulator TRA2A for further characterization. In a FXTAS cellular model we validated TRA2A-FRM1 interaction and investigated implications of its sequestration at both transcriptomic and post-transcriptomic levels. We found that TRA2A co-aggregates with FMR1 in a FXTAS mouse model and in post mortem human samples.\n\nOur integrative study identifies key components of ribonucleoprotein aggregates, providing links to neurodegenerative disease and allowing the discovery of new therapeutic targets.