RESUMEN
Hypoxia induces profound modifications in the gene expression program of eukaryotic cells due to lowered ATP supply resulting from the blockade of oxidative phosphorylation. One significant consequence of oxygen deprivation is the massive repression of protein synthesis, leaving a limited set of mRNAs to be translated. Drosophila melanogaster is strongly resistant to oxygen fluctuations; however, the mechanisms allowing specific mRNA to be translated into hypoxia are still unknown. Here, we show that Ldh mRNA encoding lactate dehydrogenase is highly translated into hypoxia by a mechanism involving a CA-rich motif present in its 3' untranslated region. Furthermore, we identified the cap-binding protein eIF4EHP as a main factor involved in 3'UTR-dependent translation under hypoxia. In accordance with this observation, we show that eIF4EHP is necessary for Drosophila development under low oxygen concentrations and contributes to Drosophila mobility after hypoxic challenge. Altogether, our data bring new insight into mechanisms contributing to LDH production and Drosophila adaptation to oxygen variations.
Asunto(s)
Drosophila melanogaster , Hipoxia , Animales , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Hipoxia/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Drosophila/genética , Drosophila/metabolismo , Oxígeno/metabolismo , Regiones no Traducidas 3' , L-Lactato Deshidrogenasa/genética , L-Lactato Deshidrogenasa/metabolismo , Biosíntesis de ProteínasRESUMEN
Programmed ribosomal frameshifting is a key event during translation of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA genome that allows synthesis of the viral RNA-dependent RNA polymerase and downstream proteins. Here, we present the cryo-electron microscopy structure of a translating mammalian ribosome primed for frameshifting on the viral RNA. The viral RNA adopts a pseudoknot structure that lodges at the entry to the ribosomal messenger RNA (mRNA) channel to generate tension in the mRNA and promote frameshifting, whereas the nascent viral polyprotein forms distinct interactions with the ribosomal tunnel. Biochemical experiments validate the structural observations and reveal mechanistic and regulatory features that influence frameshifting efficiency. Finally, we compare compounds previously shown to reduce frameshifting with respect to their ability to inhibit SARS-CoV-2 replication, establishing coronavirus frameshifting as a target for antiviral intervention.
