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YoeB toxin is activated during thermal stress.

Janssen BD, Garza-Sánchez F, Hayes CS - Microbiologyopen (2015)

Bottom Line: Moreover, heat-activated YoeB does not induce growth arrest nor does it suppress global protein synthesis.In fact, E. coli cells proliferate more rapidly at elevated temperatures and instantaneously accelerate their growth rate in response to acute heat shock.We propose that heat-activated YoeB may serve a quality control function, facilitating the recycling of stalled translation complexes through ribosome rescue pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California.

No MeSH data available.


Related in: MedlinePlus

Cell growth is not arrested during heat shock. (A) & (B) E. coli cells with the indicated genotypes were grown in shaking LB broth at 30°C for 2.5 h, then shifted to 42°C (indicated by the upward arrow) for continued culture. Cell growth was monitored by optical density at 600 nm (OD600).
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fig07: Cell growth is not arrested during heat shock. (A) & (B) E. coli cells with the indicated genotypes were grown in shaking LB broth at 30°C for 2.5 h, then shifted to 42°C (indicated by the upward arrow) for continued culture. Cell growth was monitored by optical density at 600 nm (OD600).

Mentions: The stress-response model of TA function postulates that environmental stress activates mRNase toxins to temporarily inhibit translation while transcription is redirected to stress-response genes (Gerdes et al. 2005). Because YoeB is activated at high temperature, we asked whether acute heat shock leads to temporary growth arrest as predicted by the stress-response model. We monitored the growth of wild-type yoeB+ cells and observed no inhibition of growth during the transition from 30°C to 42°C (Fig.7A). Moreover, ΔyefM-yoeB mutants grew along the same trajectory as yefM-yoeB+ cells during the heat-shock treatment (Fig.7A). These results indicate that YoeB activity is not sufficient to arrest growth, consistent with the absence of detectable cleavage within endogenous messages at 42°C. tmRNA facilitates ribosome recycling after YoeB-mediated A-site cleavage, so we also examined the response of ssrA− cells to heat shock. Although ssrA− mutants grow more slowly than ssrA+ cells at 30°C and 42°C, the ΔyefM-yoeB mutation had little effect in this background (Fig.7B). Because YoeB activity persists over at least 2 h of culture at 42°C, we examined whether the toxin influences cell growth over longer time scales. We spotted yefM-yoeB+ and ΔyefM-yoeB cells onto LB agar for overnight incubation at temperatures ranging from 30°C to 46°C, but observed no differences in cell growth in various ssrA and lon backgrounds (Fig.8). In fact, the most prominent growth defects were observed with ssrA− cells at 46°C and Δlon cells at 30°C. The ssrA mutation reduced cell growth at 46°C about 10-fold in the yefM-yoeB and lon backgrounds (Fig.8). Additionally, Δlon cells grew more slowly than lon+ cells on solid medium at 30°C, and this effect was even more pronounced in the ssrA− background (Fig.8). Together, these results indicate that tmRNA and Lon contribute to fitness at high and low temperatures, but YefM and YoeB do not confer a discernible advantage under these conditions.


YoeB toxin is activated during thermal stress.

Janssen BD, Garza-Sánchez F, Hayes CS - Microbiologyopen (2015)

Cell growth is not arrested during heat shock. (A) & (B) E. coli cells with the indicated genotypes were grown in shaking LB broth at 30°C for 2.5 h, then shifted to 42°C (indicated by the upward arrow) for continued culture. Cell growth was monitored by optical density at 600 nm (OD600).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4554461&req=5

fig07: Cell growth is not arrested during heat shock. (A) & (B) E. coli cells with the indicated genotypes were grown in shaking LB broth at 30°C for 2.5 h, then shifted to 42°C (indicated by the upward arrow) for continued culture. Cell growth was monitored by optical density at 600 nm (OD600).
Mentions: The stress-response model of TA function postulates that environmental stress activates mRNase toxins to temporarily inhibit translation while transcription is redirected to stress-response genes (Gerdes et al. 2005). Because YoeB is activated at high temperature, we asked whether acute heat shock leads to temporary growth arrest as predicted by the stress-response model. We monitored the growth of wild-type yoeB+ cells and observed no inhibition of growth during the transition from 30°C to 42°C (Fig.7A). Moreover, ΔyefM-yoeB mutants grew along the same trajectory as yefM-yoeB+ cells during the heat-shock treatment (Fig.7A). These results indicate that YoeB activity is not sufficient to arrest growth, consistent with the absence of detectable cleavage within endogenous messages at 42°C. tmRNA facilitates ribosome recycling after YoeB-mediated A-site cleavage, so we also examined the response of ssrA− cells to heat shock. Although ssrA− mutants grow more slowly than ssrA+ cells at 30°C and 42°C, the ΔyefM-yoeB mutation had little effect in this background (Fig.7B). Because YoeB activity persists over at least 2 h of culture at 42°C, we examined whether the toxin influences cell growth over longer time scales. We spotted yefM-yoeB+ and ΔyefM-yoeB cells onto LB agar for overnight incubation at temperatures ranging from 30°C to 46°C, but observed no differences in cell growth in various ssrA and lon backgrounds (Fig.8). In fact, the most prominent growth defects were observed with ssrA− cells at 46°C and Δlon cells at 30°C. The ssrA mutation reduced cell growth at 46°C about 10-fold in the yefM-yoeB and lon backgrounds (Fig.8). Additionally, Δlon cells grew more slowly than lon+ cells on solid medium at 30°C, and this effect was even more pronounced in the ssrA− background (Fig.8). Together, these results indicate that tmRNA and Lon contribute to fitness at high and low temperatures, but YefM and YoeB do not confer a discernible advantage under these conditions.

Bottom Line: Moreover, heat-activated YoeB does not induce growth arrest nor does it suppress global protein synthesis.In fact, E. coli cells proliferate more rapidly at elevated temperatures and instantaneously accelerate their growth rate in response to acute heat shock.We propose that heat-activated YoeB may serve a quality control function, facilitating the recycling of stalled translation complexes through ribosome rescue pathways.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California.

No MeSH data available.


Related in: MedlinePlus