RESUMO
Regulation of protein synthesis is critical for control of gene expression in all cells. Ribosomes are ribonucleoprotein machines responsible for translating cellular proteins. Defects in ribosome production, function, or regulation are detrimental to the cell and cause human diseases, such as progressive encephalopathy with edema, hypsarrhythmia, and optic atrophy (PEHO) syndrome. PEHO syndrome is a devastating neurodevelopmental disorder caused by mutations in the ZNHIT3 gene, which encodes an evolutionarily conserved nuclear protein. The precise mechanisms by which ZNHIT3 mutations lead to PEHO syndrome are currently unclear. Studies of the human zinc finger HIT-type containing protein 3 homolog in budding yeast (Hit1) revealed that this protein is critical for formation of small nucleolar ribonucleoprotein complexes that are required for rRNA processing and 2'-O-methylation. Here, we use budding yeast as a model system to reveal the basis for the molecular pathogenesis of PEHO syndrome. We show that missense mutations modeling those found in PEHO syndrome patients cause a decrease in steady-state Hit1 protein levels, a significant reduction of box C/D snoRNA levels, and subsequent defects in rRNA processing and altered cellular translation. Using RiboMethSeq analysis of rRNAs isolated from actively translating ribosomes, we reveal site-specific changes in the rRNA modification pattern of PEHO syndrome mutant yeast cells. Our data suggest that PEHO syndrome is a ribosomopathy and reveal potential new aspects of the molecular basis of this disease in translation dysregulation.
Assuntos
Edema Encefálico , Doenças Neurodegenerativas , Proteínas Nucleares , Atrofia Óptica , Ribonucleoproteínas Nucleolares Pequenas , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Espasmos Infantis , Fatores de Transcrição , Edema Encefálico/genética , Humanos , Recém-Nascido , Mutação , Doenças Neurodegenerativas/genética , Proteínas Nucleares/genética , Atrofia Óptica/genética , RNA Nucleolar Pequeno/metabolismo , Ribonucleoproteínas Nucleolares Pequenas/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Espasmos Infantis/genética , Fatores de Transcrição/genéticaRESUMO
SignificanceThe presence of RNA chemical modifications has long been known, but their precise molecular consequences remain unknown. 2'-O-methylation is an abundant modification that exists in RNA in all domains of life. Ribosomal RNA (rRNA) represents a functionally important RNA that is heavily modified by 2'-O-methylations. Although abundant at functionally important regions of the rRNA, the contribution of 2'-O-methylations to ribosome activities is unknown. By establishing a method to disturb rRNA 2'-O-methylation patterns, we show that rRNA 2'-O-methylations affect the function and fidelity of the ribosome and change the balance between different ribosome conformational states. Our work links 2'-O-methylation to ribosome dynamics and defines a set of critical rRNA 2'-O-methylations required for ribosome biogenesis and others that are dispensable.
