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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

Thermal-induced YoeB activity is not detected on endogenous transcripts. (A) Total RNA from cells grown at 30°C and 42°C was analyzed by northern hybridization using oligonucleotide probes to the 5′- and 3′-untranslated regions of lpp mRNA in yoeB+ and ΔyefM-yoeB (ΔyoeB) backgrounds. (B) The same RNA samples from (A) were analyzed by northern hybridization using probes to the 5′-UTRs of grpE and ibpB messages.
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fig06: Thermal-induced YoeB activity is not detected on endogenous transcripts. (A) Total RNA from cells grown at 30°C and 42°C was analyzed by northern hybridization using oligonucleotide probes to the 5′- and 3′-untranslated regions of lpp mRNA in yoeB+ and ΔyefM-yoeB (ΔyoeB) backgrounds. (B) The same RNA samples from (A) were analyzed by northern hybridization using probes to the 5′-UTRs of grpE and ibpB messages.

Mentions: Previous work has shown that YoeB cleaves ompA and lpp transcripts in E. coli (Winther and Gerdes 2009; Zhang and Inouye 2009). Therefore, we tested whether YoeB cleaves these endogenous mRNAs in response to elevated temperature. We were unable to detect truncated lpp transcripts using probes to the 5′- and 3′-untranslated regions (Fig.6A). Similarly, the ompA transcript was not cleaved during culture at 42°C (data not shown). We also considered the possibility that YoeB may preferentially cleave heat-shock transcripts and provide a mechanism to fine-tune their translation. However, we did not detect yoeB-dependent cleavage in grpE and ibpB transcripts in response to growth at 42°C (Fig.6B). Although smaller ibpB transcripts were detected at 42°C in ssrA− cells, these fragments accumulated to similar levels in both yoeB+ and ΔyoeB backgrounds (Fig.6B). These data are seemingly at odds with the observation that flag-(m)ybeL-PP reporter transcripts are efficiently cleaved under the same growth conditions. We hypothesize that YoeB activity is focused on the reporter transcript due to a combination of overexpression and inefficient translation termination. We have shown previously that the entire pool of release factor-1 (RF-1) is sequestered on paused ribosomes during ybeL-PP overexpression (Janssen and Hayes 2009). RF-1 depletion then causes other ribosomes to stall at the ybeL-PP termination codon with unoccupied A sites (Janssen and Hayes 2009). Because YoeB must compete with translation factors to gain access to its A-site codon substrate, we propose that these latter ribosomes with unoccupied A sites are preferentially targeted by the nuclease.


YoeB toxin is activated during thermal stress.

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

Thermal-induced YoeB activity is not detected on endogenous transcripts. (A) Total RNA from cells grown at 30°C and 42°C was analyzed by northern hybridization using oligonucleotide probes to the 5′- and 3′-untranslated regions of lpp mRNA in yoeB+ and ΔyefM-yoeB (ΔyoeB) backgrounds. (B) The same RNA samples from (A) were analyzed by northern hybridization using probes to the 5′-UTRs of grpE and ibpB messages.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4554461&req=5

fig06: Thermal-induced YoeB activity is not detected on endogenous transcripts. (A) Total RNA from cells grown at 30°C and 42°C was analyzed by northern hybridization using oligonucleotide probes to the 5′- and 3′-untranslated regions of lpp mRNA in yoeB+ and ΔyefM-yoeB (ΔyoeB) backgrounds. (B) The same RNA samples from (A) were analyzed by northern hybridization using probes to the 5′-UTRs of grpE and ibpB messages.
Mentions: Previous work has shown that YoeB cleaves ompA and lpp transcripts in E. coli (Winther and Gerdes 2009; Zhang and Inouye 2009). Therefore, we tested whether YoeB cleaves these endogenous mRNAs in response to elevated temperature. We were unable to detect truncated lpp transcripts using probes to the 5′- and 3′-untranslated regions (Fig.6A). Similarly, the ompA transcript was not cleaved during culture at 42°C (data not shown). We also considered the possibility that YoeB may preferentially cleave heat-shock transcripts and provide a mechanism to fine-tune their translation. However, we did not detect yoeB-dependent cleavage in grpE and ibpB transcripts in response to growth at 42°C (Fig.6B). Although smaller ibpB transcripts were detected at 42°C in ssrA− cells, these fragments accumulated to similar levels in both yoeB+ and ΔyoeB backgrounds (Fig.6B). These data are seemingly at odds with the observation that flag-(m)ybeL-PP reporter transcripts are efficiently cleaved under the same growth conditions. We hypothesize that YoeB activity is focused on the reporter transcript due to a combination of overexpression and inefficient translation termination. We have shown previously that the entire pool of release factor-1 (RF-1) is sequestered on paused ribosomes during ybeL-PP overexpression (Janssen and Hayes 2009). RF-1 depletion then causes other ribosomes to stall at the ybeL-PP termination codon with unoccupied A sites (Janssen and Hayes 2009). Because YoeB must compete with translation factors to gain access to its A-site codon substrate, we propose that these latter ribosomes with unoccupied A sites are preferentially targeted by the nuclease.

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