A Yeast Model of FUS/TLS-Dependent Cytotoxicity

Fus/tls is a nucleic acid binding protein that,when mutated,can cause a subset of familial amyotrophic lateral sclerosis (fals). although fus/tls is normally located predominantly in the nucleus,the pathogenic mutant forms of fus/tls traffic to,and form inclusions in,the cytoplasm of affected spinal motor neurons or glia. here we report a yeast model of human fus/tls expression that recapitulates multiple salient features of the pathology of the disease-causing mutant proteins,including nuclear to cytoplasmic translocation,inclusion formation,and cytotoxicity. protein domain analysis indicates that the carboxyl-terminus of fus/tls,where most of the als-associated mutations are clustered,is required but not sufficient for the toxicity of the protein. a genome-wide genetic screen using a yeast over-expression library identified five yeast dna/rna binding proteins,encoded by the yeast genes ecm32,nam8,sbp1,sko1,and vhr1,that rescue the toxicity of human fus/tls without changing its expression level,cytoplasmic translocation,or inclusion formation. furthermore,hupf1,a human homologue of ecm32,also rescues the toxicity of fus/tls in this model,validating the yeast model and implicating a possible insufficiency in rna processing or the rna quality control machinery in the mechanism of fus/tls mediated toxicity. examination of the effect of fus/tls expression on the decay of selected mrnas in yeast indicates that the nonsense-mediated decay pathway is probably not the major determinant of either toxicity or suppression. © 2011 ju et al.