Structure and function of human ribosome complexes – HumanRibosome

The ribosome is a molecular machinery that comprises two subunits composed of RNAs and proteins where the small subunit is responsible for mRNA decoding and the large subunit catalyses peptide bond formation. Various prokaryotic and eukaryotic ribosome structures have provided important insights into the mechanism of protein synthesis. Our objective is to study the human ribosome and address the associated molecular mechanisms underlying protein synthesis regulation and de-regulation. Many antibiotics target the bacterial ribosome by interfering with mechanistic steps of the protein synthesis machinery (initiation, elongation, termination and other regulatory mechanisms), but issues of selectivity can arise from the fact that typical antibiotic binding sites are largely conserved in bacterial, human and mitochondrial ribosomes. Beyond the well-known problem of growing resistance of bacteria, another major, but less considered aspect arises from the fact that deregulation of protein synthesis in human is involved in various diseases, e.g. immune disorders, neurodegeneration and cancer, and that ribosomes showing elevated protein synthesis rates in human cells may constitute a good target for new therapeutics. A fundamental concept in this project is that new-generation drugs targeting the human ribosome should be conceived to not entirely block, but rather modulate protein synthesis rates by interfering differentially with the translation machinery of deregulated cells. This leads to at least two major potential applications: (i) reducing side-effects of current antibiotics by improving drug specificity, and oppositely (ii) developing new agents that target the human ribosome to specifically affect the elevated protein synthesis rates of deregulated and more sensitive cells that makes them a primary target over normally growing cells. Until recently, it was not possible to envisage studying the molecular basis of ligand actions on human ribosome function because the structure of the human ribosome was unknown. This has now changed drastically thanks to the recently obtained first high-resolution structure of the human ribosome using advanced high-resolution cryo electron microscopy (cryo-EM) (partner 1: Khatter et al., Nature 2015). Our research strategy consists in combining the knowledge of determining the structure of human ribosome complexes by cryo-EM (partner 1, Bruno Klaholz) with functional assays of potential ligands on human cell lines (partner 2, Jean-François Peyron), allowing in the future to envisage structure-assisted drug design to target the human ribosome. The aim of the project is therefore to analyse the molecular basis for ligand binding and the mechanism of action on the human ribosome in order to characterize it as a potential target for drugs. The structure-function relationship of ligand and also of factor complexes to address the molecular mechanism of inhibition will be studied through an integrative biology approach including cutting-edge structural biology methods such as advanced high-resolution cryo-EM, cell biology and functional tests. Latest results by partner 1 show that human ribosome structures can now be obtained in the 2.5-3.0 Å resolution range, opening totally novel possibilities for the analysis of the human ribosome and its functional complexes with ligands, mRNA, tRNA and ribosomal factors. Thus, this project opens up many new research opportunities in translational medicine and perfectly fits with the Life, Health and Well-being section of the PRC call to address fundamental molecular mechanisms in biology with a strong potential for research and innovation in the field of biomedical research. Important new insights can be expected from this innovative project, which in the future could contribute to the development of novel therapeutic applications that can be transferred to academic and pharmaceutical partners.