The Escherichia coli mazEF Suicide Module Mediates Thymineless Death

Abstract

In 1954, Cohen and Barner discovered that a thymine auxotrophic (thyA) mutant of Escherichia coli undergoes cell death in response to thymine starvation. This phenomenon, called thymineless death (TLD), has also been found in many other organisms, including prokaryotes and eukaryotes. Though TLD has been studied intensively, its molecular mechanism has not yet been explained. Previously we reported on the E. coli mazEF system, a regulatable chromosomal suicide module that can be triggered by various stress conditions. MazF is a stable toxin, and MazE is an unstable antitoxin. Here, we show that cell death that is mediated by the mazEF module can also be activated by thymine starvation. We found that TLD depends on E. coli mazEF and that under thymine starvation, the activity of the mazEF promoter P 2 is significantly reduced. Our results, which describe thymine starvation as a trigger for a built-in death program, have implications for programmed cell death in both prokaryotes and eukaryotes.

MazF ribonucleases promote Mycobacterium tuberculosis drug tolerance and virulence in guinea pigs

“…The E. coli MazF protein cleaves both mRNA and 16S ribosomal RNA, and is proposed to generate a subpopulation of stress ribosomes, thereby enabling the translation of leaderless transcripts 19 . MazEF systems in E. coli are activated on exposure to numerous stress conditions in an extracellular death factor-dependent manner [20][21][22] . In E. coli, MazF-mediated drug-induced persistence is RecA independent, but dependent on ClpP and Lon proteases 23 .…”

Looking for death at the core of life in the light of evolution

“…[72][73][74] Indeed, the repression of the expression of at least two different chromosomal toxin/ antidote modules -triggered in part of the colony in response to nutrient deprival, and resulting in antidote degradation and free toxin availability -can, depending on the circumstances, have two opposite outcomes in terms of life and death. It can either trigger bacterial death 'from within', 59,74 or paradoxically favor the survival of the free toxin-containing cell, 72,73 for example, through selective toxin-mediated inhibition of protein synthesis at the ribosomal level, and thus inhibition of energy consumption. If nutrients subsequently become available, the re-expression of the toxin/antidote module will allow the de novo synthesis of the antidote, leading to the neutralization of the toxin, and allowing the bacteria cell to resume normal metabolism and activity.…”

A continuous fluorometric assay for the assessment of MazF ribonuclease activity

“…Such TA systems are sometimes referred to as "plasmid addiction" modules [7,8]. The precise role of TA systems encoded by bacterial chromosomes is less clear, but there is evidence that they may serve as stress response elements, as toxin-induced cell death is observed under conditions including high temperatures, DNA damage, oxidative stress [9], thymine starvation [10], and antibiotic treatment [11]. In addition, the transcription of genes from chromosomally encoded TA loci are upregulated during amino acid starvation [12,13].…”

“…Most proteic TA systems are characterized by two small (8)(9)(10)(11)(12)(13)(14)(15) proteins, a stable toxin and a labile antitoxin, and genes encoding these proteins have been identified on a wide range of bacterial chromosomes and plasmids [4,5]. If both proteins are actively being produced by the bacterial cell, the antitoxin binds the toxin and inhibits its toxic activity.…”