Widespread ribosome stalling in a genome-reduced bacterium and the need for translational quality control

Burgos, Raul; Weber, Marc; Gallo López, Carolina, 1984-; Lluch-Senar, Maria 1982-; Serrano Pubull, Luis, 1982-

doi:http://dx.doi.org/10.1016/j.isci.2021.102985

Widespread ribosome stalling in a genome-reduced bacterium and the need for translational quality control

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Burgos R, Weber M, Gallo C, Lluch-Senar M, Serrano L. Widespread ribosome stalling in a genome-reduced bacterium and the need for translational quality control. iScience. 2021 Aug 16;24(9):102985. DOI: 10.1016/j.isci.2021.102985

Abstract

Trans-translation is a ubiquitous bacterial mechanism of ribosome rescue mediated by a transfer-messenger RNA (tmRNA) that adds a degradation tag to the truncated nascent polypeptide. Here, we characterize this quality control system in a genome-reduced bacterium, Mycoplasma pneumoniae (MPN), and perform a comparative analysis of protein quality control components in slow and fast-growing prokaryotes. We show in vivo that in MPN the sole quality control cytoplasmic protease (Lon) degrades efficiently tmRNA-tagged proteins. Analysis of tmRNA-mutants encoding a tag resistant to proteolysis reveals extensive tagging activity under normal growth. Unlike knockout strains, these mutants are viable demonstrating the requirement of tmRNA-mediated ribosome recycling. Chaperone and Lon steady-state levels maintain proteostasis in these mutants suggesting a model in which co-evolution of Lon and their substrates offer simple mechanisms of regulation without specialized degradation machineries. Finally, comparative analysis shows relative increase in Lon/Chaperone levels in slow-growing bacteria suggesting physiological adaptation to growth demand.