RESUMO
Translation and ribosome biogenesis in mitochondria require auxiliary factors that ensure rapid and accurate synthesis of mitochondrial proteins. Defects in translation are associated with oxidative phosphorylation deficiency and cause severe human diseases, but the exact roles of mitochondrial translation-associated factors are not known. Here we identify the functions of GTPBP6, a homolog of the bacterial ribosome-recycling factor HflX, in human mitochondria. Similarly to HflX, GTPBP6 facilitates the dissociation of ribosomes in vitro and in vivo. In contrast to HflX, GTPBP6 is also required for the assembly of mitochondrial ribosomes. GTPBP6 ablation leads to accumulation of late assembly intermediate(s) of the large ribosomal subunit containing ribosome biogenesis factors MTERF4, NSUN4, MALSU1 and the GTPases GTPBP5, GTPBP7 and GTPBP10. Our data show that GTPBP6 has a dual function acting in ribosome recycling and biogenesis. These findings contribute to our understanding of large ribosomal subunit assembly as well as ribosome recycling pathway in mitochondria.
Assuntos
Proteínas de Ligação ao GTP/genética , Mitocôndrias/genética , Proteínas Mitocondriais/genética , Ribossomos Mitocondriais , GTP Fosfo-Hidrolases/genética , Humanos , Metiltransferases/genética , Proteínas Monoméricas de Ligação ao GTP/genética , Biossíntese de Proteínas/genética , Proteínas Ribossômicas/genética , Fatores de Transcrição/genéticaRESUMO
The human mitochondrial translation apparatus, which synthesizes the core subunits of the oxidative phosphorylation system, is of central interest as mutations in several genes encoding for mitoribosomal proteins or translation factors cause severe human diseases. Little is known, how this complex machinery assembles from nuclear-encoded protein components and mitochondrial-encoded RNAs, and which ancillary factors are required to form a functional mitoribosome. We have characterized the human Obg protein GTPBP10, which associates specifically with the mitoribosomal large subunit at a late maturation state. Defining its interactome, we have shown that GTPBP10 is in a complex with other mtLSU biogenesis factors including mitochondrial RNA granule components, the 16S rRNA module and late mtLSU assembly factors such as MALSU1, SMCR7L, MTERF4 and NSUN4. GTPBP10 deficiency leads to a drastic reduction in 55S monosome formation resulting in defective mtDNA-expression and in a decrease in cell growth. Our results suggest that GTPBP10 is a ribosome biogenesis factor of the mtLSU required for late stages of maturation.
