Abstract
RNA exosomopathies, a growing family of tissue-specific diseases, are linked to missense mutations in genes encoding the structural subunits of the highly conserved 10-subunit riboexonuclease complex termed the RNA exosome. Such mutations in the cap subunit gene EXOSC2 cause the novel syndrome SHRF (Short stature, Hearing loss, Retinitis pigmentosa and distinctive Facies). In contrast, exosomopathy mutations in the cap subunit gene EXOSC3 cause pontocerebellar hypoplasia type 1b (PCH1b). Though the mutations in EXOSC2 and EXOSC3 cause strikingly different disease pathologies, the pathogenic mutations in these two genes result in amino acid substitutions in similar, conserved domains of the cap subunits, suggesting that these pathogenic mutations have distinct consequences for RNA exosome function. We generated the first in vivo model of the SHRF pathogenic amino acid substitutions using budding yeast by introducing the EXOSC2 mutations in the orthologous S. cerevisiae gene RRP4. The resulting rrp4 mutant cells have defects in cell growth and RNA exosome function. We detect significant transcriptomic changes in both coding and noncoding RNAs in the rrp4 mutant, rrp4-G226D, which models EXOSC2 p.Gly198Asp. Comparing this rrp4-G226D mutant to the previously studied S. cerevisiae model of EXOSC3 PCH1b mutations, rrp40-W195R reveals that these mutants have some similar but some different effects on RNA targets, providing the first evidence for different mechanistic consequences of these pathogenic amino acid changes. Consistent with this model, we detect specific negative genetic interactions between RNA exosome cofactor mutants and rrp4-G226D but not rrp40-W195R. These data provide insight into how SHRF mutations could alter the function of the RNA exosome and allow the first direct comparison of exosomopathy mutations that cause distinct pathologies.
Competing Interest Statement
The authors have declared no competing interest.