Conserved heterodimeric GTPase Rbg1/Tma46 promotes efficient translation in eukaryotic cells

Conserved developmentally regulated guanosine triphosphate (GTP)-binding proteins (Drgs) and their binding partner Drg family regulatory proteins (Dfrps) are important for embryonic development, cellular growth control, differentiation, and proliferation. Here, we report that the yeast Drg1/Dfrp1 ortholog Rbg1/Tma46 facilitates translational initiation, elongation, and termination by suppressing prolonged ribosome pausing. Consistent with the genome-wide observations, deletion of Rbg1 exacerbates the growth defect resulting from translation stalling, and Rbg1 stabilizes mRNAs against no-go decay. Furthermore, we provide a cryoelectron microscopy (cryo-EM) structure of the 80S ribosome bound with Rbg1/Tma46 that reveals the molecular interactions responsible for Rbg1/Tma46 function. The Rbg1 subunit binds to the GTPase association center of the ribosome and the A-tRNA, and the N-terminal zinc finger domain of the Tma46 subunit binds to the 40S, establishing an interaction critical for the ribosomal association. Our results answer the fundamental question of how a paused ribosome resumes translation and show that Drg1/Dfrp1 play a critical role in ensuring orderly translation.