Role of 100S ribosomes in bacterial decay period

Abstract

Ribosomal proteins S10 and S2 were each fused with GFP to track the fates of these proteins in the stationary growth phase and the following decay period in Escherichia coli. The fused proteins localized mainly in the cytoplasm, and their amounts were proportional to the colony-forming unit. S10-GFP strains that lacked genes responsible for regulating 100S ribosomes and S2-GFP strain that was unable to form 100S both showed shortened stationary phases. This result indicates that these strains exhibit earlier death in the absence of 100S formation (S2-GFP, S10-GFPΔrmf and S10-GFPΔhpf) and breakdown (S10-GFPΔyfiA). Therefore, in addition to the mere presence of 100S, the correct timing of 100S formation and breakdown is required to maintain viability. We propose a model in which 100S acts as a tentative repository of ribosomes that are protected from degradation and provide a source of amino acids in later growth period.

Structure of the Bacillus subtilis hibernating 100S ribosome reveals the basis for 70S dimerization

“…Moreover, it remains unclear how hibernating 100S ribosomes exactly provide protection against stress. What is clear however is that in the absence of 100S, 70S ribosomes are slowly degraded leading to early cell death, suggesting that hibernating 100S are less susceptible to degradation by RNases (Fukuchi et al, 1995;Wada, 1998;Niven, 2004;Shcherbakova et al, 2015;Akanuma et al, 2016). Because 100S formation does not significantly alter the large rRNA surface exposed to RNases, we believe LHPF binding and 100S formation may interfere with a specific ribosome degradation pathway, rather than preventing non-specific RNase action on ribosomes.…”

“…In this model, we propose that BsHPF utilizes the free NTDs and long linker to initially bring 70S ribosomes into close proximity, and then further stabilizes the 70S dimer using the BsHPF-CTD ribosome interface (Fig 7B). What is clear however is that in the absence of 100S, 70S ribosomes are slowly degraded leading to early cell death, suggesting that hibernating 100S are less susceptible to degradation by RNases (Fukuchi et al, 1995;Wada, 1998;Niven, 2004;Shcherbakova et al, 2015;Akanuma et al, 2016). Moreover, it remains unclear how hibernating 100S ribosomes exactly provide protection against stress.…”

“…Under such circumstances, the decrease in translational activity is correlated with the appearance of 100S particles, which arise due to the dimerization of 70S ribosomes (Wada et al, 1990), reviewed by Yoshida and Wada (2014). The hibernation state (Yoshida et al, 2002) appears to be important for bacterial survival since inactivation of the rmf gene leads to loss of viability in stationary phase cells (Yamagishi et al, 1993;Wada et al, 2000;Shcherbakova et al, 2015) as well as increased sensitivity to osmotic (Garay-Arroyo et al, 2000), heat (Niven, 2004), and acid stress (El-Sharoud & Niven, 2007). Stationary phase E. coli cells also express a homolog of HPF (Fig 1A), termed YfiA (also referred to as pY or RaiA), which binds and inactivates 70S ribosomes (Agafonov & Spirin, 2004;Vila-Sanjurjo et al, 2004), and is antagonistic to RMF and HPF action by preventing 100S formation (Maki et al, 2000;Ueta et al, 2005).…”

“…Stationary phase E. coli cells also express a homolog of HPF ( Fig 1A), termed YfiA (also referred to as pY or RaiA), which binds and inactivates 70S ribosomes (Agafonov & Spirin, 2004;Vila-Sanjurjo et al, 2004), and is antagonistic to RMF and HPF action by preventing 100S formation (Maki et al, 2000;Ueta et al, 2005). The hibernation state (Yoshida et al, 2002) appears to be important for bacterial survival since inactivation of the rmf gene leads to loss of viability in stationary phase cells (Yamagishi et al, 1993;Wada et al, 2000;Shcherbakova et al, 2015) as well as increased sensitivity to osmotic (Garay-Arroyo et al, 2000), heat (Niven, 2004), and acid stress (El-Sharoud & Niven, 2007).…”

Disassembly of theStaphylococcus aureushibernating 100S ribosome by an evolutionarily conserved GTPase

“…A common feature of these biological processes is that cells generally conserve energy by undergoing metabolic and translational dormancy because protein synthesis accounts for >50% of energy costs (12,13). The dimerization of 70S ribosomes has been shown to down-regulate translational efficiency in vivo (3) and in vitro (3,14), and bacteria lacking 100S ribosomes are prone to early cell death concomitant with rapid ribosome degradation (3,10,15,16). These studies lead to a model whereby the formation of the 100S complex sequesters the ribosome pool away from active translation, and 70S self-dimerization prevents ribosome degradation by an unknown pathway (3,17).…”