RNA-Binding Protein TAF15 Suppresses Toxicity in a Yeast Model of FUS Proteinopathy

Mutations in an RNA-binding protein FUS are known to cause familial amyotrophic lateral sclerosis (ALS). Since this discovery, mutations in several other RNA-binding proteins (RBPs) have also been linked to ALS. Some of these ALS-associated RBPs have been shown to colocalize with ribonucleoprotein (RNP) granules such as stress granules and processing bodies (p-bodies). Increasing evidence has emerged supporting a hypothesis that the impaired clearance, inappropriate assembly, and dysregulation of RNP granules play a role in ALS. Through the genome-scale overexpression screening of a yeast model of FUS toxicity, we found that TAF15, a human RBP with a similar protein domain structure and belonging to the same FET protein family as FUS, suppresses FUS toxicity in yeast. The suppression by TAF15 is specific to FUS and not found in other yeast models of neurodegenerative disease-associated proteins. We showed that the RNA recognition motif (RRM) of TAF15 is required for its suppression of FUS toxicity. Furthermore, FUS and TAF15 physically interact, and the C-terminus of TAF15 is required for both the physical protein-protein interaction and its protection against FUS toxicity. Finally, while FUS induces and colocalizes with both stress granules and p-bodies, TAF15 only induces and colocalizes with p-bodies. Importantly, the co-expression of FUS and TAF15 induces more p-bodies than individually expressing each gene alone, and FUS toxicity is exacerbated in yeast that is deficient in p-body formation. Overall, our findings suggest a role of increased p-body formation in the suppression of FUS toxicity by TAF15.