title: YoeB toxin is activated during thermal stress.
abstract: Type II toxin-antitoxin (TA) modules are thought to mediate stress-responses by temporarily suppressing protein synthesis while cells redirect transcription to adapt to environmental change. Here, we show that YoeB, a ribosome-dependent mRNase toxin, is activated in Escherichia coli cells grown at elevated temperatures. YoeB activation is dependent on Lon protease, suggesting that thermal stress promotes increased degradation of the YefM antitoxin. Though YefM is efficiently degraded in response to Lon overproduction, we find that Lon antigen levels do not increase during heat shock, indicating that another mechanism accounts for temperature-induced YefM proteolysis. These observations suggest that YefM/YoeB functions in adaptation to temperature stress. However, this response is distinct from previously described models of TA function. First, YoeB mRNase activity is maintained over several hours of culture at 42°C, indicating that thermal activation is not transient. 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.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Janssen
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California.
authors.forename: Fernando
authors.initials: F
authors.lastname: Garza-Sánchez
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, California.|Biomolecular Science and Engineering Program, University of California, Santa Barbara, Santa Barbara, California.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Hayes
mesh_terms: D001427:Bacterial Toxins / Q000378:metabolism*; D004926:Escherichia coli / Q000254:growth & development / Q000528:radiation effects*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D049070:Protease La / Q000378:metabolism; D059748:Proteolysis; D013696:Temperature
chemical_list: D001427:Bacterial Toxins; D029968:Escherichia coli Proteins; C484519:YefM protein, E coli; C504245:YoeB protein, E coli; C483567:Lon protein, E coli; D049070:Protease La
keywords: A-site mRNA cleavage; RNase II; mRNA turnover; ribosome pausing; tmRNA