Loss of Ribosomal Protein L11 Blocks Stress Activation of the Bacillus subtilis Transcription Factor ς ^B

Abstract

general stress response sigma factor of Bacillus subtilis, is activated when the cell's energy levels decline or the bacterium is exposed to environmental stress (e.g., heat shock, ethanol). Physical stress activates B through a collection of regulatory kinases and phosphatases (the Rsb proteins) which catalyze the release of B from an anti-B factor inhibitor. The means by which diverse stresses communicate with the Rsb proteins is unknown; however, a role for the ribosome in this process was suggested when several of the upstream members of the B stress activation cascade (RsbR, -S, and -T) were found to cofractionate with ribosomes in crude B. subtilis extracts. We now present evidence for the involvement of a ribosome-mediated process in the stress activation of B . B. subtilis strains resistant to the antibiotic thiostrepton, due to the loss of ribosomal protein L11 (RplK), were found to be blocked in the stress activation of B . Neither the energy-responsive activation of B nor stress-dependent chaperone gene induction (a B -independent stress response) was inhibited by the loss of L11. The Rsb proteins required for stress activation of B are shown to be active in the RplK ؊ strain but fail to be triggered by stress. The data demonstrate that the B. subtilis ribosomes provide an essential input for the stress activation of B and suggest that the ribosomes may themselves be the sensors for stress in this system.

The UV-inducible RNA-binding Protein A18 (A18 hnRNP) Plays a Protective Role in the Genotoxic Stress Response

“…On the other hand, induction of specific ribosomal proteins in response to stress may indicate the involvement of the translational machinery in the sensoring and response to cellular stress (20). The idea that ribosomes could be sensitive to stress is supported by the finding that bacterial strains lacking the ribosomal protein L11 can not activate the transcription factor sigma B in response to environmental stress (35). Moreover, the association of several ribosomal proteins with the oxidative stress response (36) is additional evidence that translation regulation is a significant component of the cellular stress response.…”

The Alternative Sigma Factor σBofBacillus cereus: Response to Stress and Role in Heat Adaptation

“…It has been proposed that in B. subtilis structural changes in the ribosome during stress could lead to induction of this pathway (51 (36). In other gram-positive bacteria, B has not been studied as extensively as it has been in B. subtilis, but there are some intriguing similarities and differences between the B responses of these organisms and the B response of B. cereus.…”

Translation Elongation by a Hybrid Ribosome in Which Proteins at the GTPase Center of the Escherichia coli Ribosome Are Replaced with Rat Counterparts

“…Not only rat RL12 but also E. coli L11, however, stimulates polyphenylalanine synthetic activity dependent on eEF-1␣ and eEF-2, although the stimulation level by RL12 is higher than that of E. coli L11. The availability of mutants deficient in L11-type proteins in bacteria (29,36,37) and yeast (38) indicates that L11-like proteins are not essential for cell viability. However, the growth rate of E. coli mutant AM68 lacking L11 was very slow; its doubling time was five times longer than strain Q13, which does have L11 (data not shown).…”