SBDS function in ribosome assembly and translational contro

Shwachman-Diamond syndrome (SDS) is a recessive disorder characterized by bone marrow failure and leukaemia predisposition. The function of the SBDS protein that is defective in SDS remains poorly understood. I hypothesise that SBDS functions as an allosteric regulator of the GTPase EFL1. I propose that SBDS promotes a conformational change in EFL1 that catalyses release of the anti-association factor eIF6 from the intersubunit face of the large ribosomal subunit by competing for an overlapping binding site. This fundamental, highly conserved process regulates the availability of free 60S subunits to enter translation in all cells. However our understanding of the underlying mechanisms is currently limited by lack of high-resolution structural data. My project aims to bypass this bottleneck by using the latest advances in single particle cryo-electron microscopy (cryo-EM). I will obtain high-resolution structures of wild-type and mutant SBDS and EFL1 proteins bound to human 60S subunits carrying eIF6. Guided by the structural analysis, I will use in vivo genetic analysis and biochemical approaches to functionally dissect the cooperative interaction between SBDS and EFL1. In thermophilic archaea, SBDS cooperates with EF2 to release eIF6. I will elucidate the fundamental conserved mechanism of eIF6 release by reconstituting functional complexes of SBDS and EF2 on archaeal 60S subunits carrying eIF6 and visualize the interactions and mechanism using single-particle cryo-EM.