Skip to main content
Advertisement

Main menu

  • Home
  • Articles
    • Accepted manuscripts
    • Issue in progress
    • Latest complete issue
    • Issue archive
    • Archive by article type
    • Special issues
    • Subject collections
    • Cell Scientists to Watch
    • First Person
    • Sign up for alerts
  • About us
    • About JCS
    • Editors and Board
    • Editor biographies
    • Travelling Fellowships
    • Grants and funding
    • Journal Meetings
    • Workshops
    • The Company of Biologists
    • Journal news
  • For authors
    • Submit a manuscript
    • Aims and scope
    • Presubmission enquiries
    • Fast-track manuscripts
    • Article types
    • Manuscript preparation
    • Cover suggestions
    • Editorial process
    • Promoting your paper
    • Open Access
    • JCS Prize
    • Manuscript transfer network
    • Biology Open transfer
  • Journal info
    • Journal policies
    • Rights and permissions
    • Media policies
    • Reviewer guide
    • Sign up for alerts
  • Contacts
    • Contact JCS
    • Subscriptions
    • Advertising
    • Feedback
  • COB
    • About The Company of Biologists
    • Development
    • Journal of Cell Science
    • Journal of Experimental Biology
    • Disease Models & Mechanisms
    • Biology Open

User menu

  • Log in

Search

  • Advanced search
Journal of Cell Science
  • COB
    • About The Company of Biologists
    • Development
    • Journal of Cell Science
    • Journal of Experimental Biology
    • Disease Models & Mechanisms
    • Biology Open

supporting biologistsinspiring biology

Journal of Cell Science

  • Log in
Advanced search

RSS   Twitter  Facebook   YouTube  

  • Home
  • Articles
    • Accepted manuscripts
    • Issue in progress
    • Latest complete issue
    • Issue archive
    • Archive by article type
    • Special issues
    • Subject collections
    • Cell Scientists to Watch
    • First Person
    • Sign up for alerts
  • About us
    • About JCS
    • Editors and Board
    • Editor biographies
    • Travelling Fellowships
    • Grants and funding
    • Journal Meetings
    • Workshops
    • The Company of Biologists
    • Journal news
  • For authors
    • Submit a manuscript
    • Aims and scope
    • Presubmission enquiries
    • Fast-track manuscripts
    • Article types
    • Manuscript preparation
    • Cover suggestions
    • Editorial process
    • Promoting your paper
    • Open Access
    • JCS Prize
    • Manuscript transfer network
    • Biology Open transfer
  • Journal info
    • Journal policies
    • Rights and permissions
    • Media policies
    • Reviewer guide
    • Sign up for alerts
  • Contacts
    • Contact JCS
    • Subscriptions
    • Advertising
    • Feedback
Commentary
mazEF: a chromosomal toxin-antitoxin module that triggers programmed cell death in bacteria
Hanna Engelberg-Kulka, Ronen Hazan, Shahar Amitai
Journal of Cell Science 2005 118: 4327-4332; doi: 10.1242/jcs.02619
Hanna Engelberg-Kulka
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Ronen Hazan
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Shahar Amitai
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • Article
  • Figures & tables
  • Info & metrics
  • PDF
Loading

Summary

mazEF is a toxin-antitoxin module located on the Escherichia coli chromosome and that of some other bacteria, including pathogens. mazF specifies for a stable toxin, MazF, and mazE specifies for a labile antitoxin, MazE, that antagonizes MazF. MazF is a sequence-specific mRNA endoribonuclease that initiates a programmed cell death pathway in response to various stresses. The mazEF-mediated death pathway can act as a defense mechanism that prevents the spread of bacterial phage infection, allowing bacterial populations to behave like multicellular organisms.

  • Programmed cell death
  • Bacterial toxin-antitoxins
  • Stressful conditions

Introduction

Programmed cell death (PCD) is as an active process that results in cell suicide and is an essential mechanism in multicellular organisms. Generally, PCD is required for the elimination of superfluous or potentially harmful cells (reviewed by Jacobson et al., 1997; Nagata, 1997). In eukaryotes, the classical form of PCD is apoptosis (Kerr et al., 1972), a term that originally defined the morphological changes that characterize this form of cell death. Today, the phrase PCD is used to refer to any form of cell death mediated by an intracellular program, no matter what triggers it and whether or not it displays all of the characteristics of apoptosis (reviewed by Jacobson et al., 1997; Raff, 1998; Hengartner, 2000).

In bacteria, the best-studied PCD systems use unique genetic modules. These modules, called addiction modules or toxin-antitoxin systems, consist of a pair of genes that encode two components: a stable toxin and an unstable antitoxin that interferes with the lethal action of the toxin. Initially, such genetic systems for bacterial PCD were found mainly in E. coli on low-copy-number plasmids, where they are responsible for what is called the post-segregational killing effect. When a bacterium loses such a plasmid (or other extrachromosomal element), the cell dies because the unstable antitoxin is degraded faster than the more-stable toxin (reviewed by Jensen and Gerdes, 1995; Yarmolinsky, 1995; Couturier et al., 1998; Engelberg-Kulka and Glaser, 1999; Hayes, 2003; Gerdes et al., 2005). The cells can be thought of as `addicted' to the short-lived product, since its de novo synthesis is essential for their survival. Thus, addiction modules maintain the stability in the host of the extrachromosomal elements on which they are borne.

Toxin-antitoxin systems, some of which are homologous to extrachromosomal addiction modules, have been found on the chromosomes of many bacteria (Mittenhuber, 1999; Engelberg-Kulka et al., 2004; Pandey and Gerdes, 2005). In E. coli, there are several toxin-antitoxin systems, including mazEF (Metzger et al., 1988; Masuda et al., 1993; Aizenman et al., 1996; Engelberg-Kulka et al., 2004), chpBIK (Masuda et al., 1993; Masuda and Ohtsubo, 1994), relBE (Bech et al., 1985; Gotfredsen and Gerdes, 1998; Gerdes et al., 2005), yefM-yoeB (Grady and Hayes, 2003; Cherney and Gazit, 2004; Christensen et al., 2004) and dinJ-yafQ (Hayes, 2003). The most studied among these is mazEF, which was the first to be discovered and described as regulatable and responsible for bacterial PCD (Metzger et al., 1988; Masuda et al., 1993; Aizenman et al., 1996). Among chromosomal toxin-antitoxin modules other than mazEF, only relBE has been studied extensively. It is not homologous to mazEF, and the structure and mode of action of the relBE products are unlike those of mazEF. Here, we focus on the mazEF system and on its relationship to PCD. In addition, we compare the modes of action and the structures of mazEF and relBE products.

mazEF is a stress-induced suicide module

The mazEF module consists of two adjacent genes, mazE and mazF, downstream of the relA gene (Metzger et al., 1988). mazEF has all the basic properties of an addiction module (Aizenman et al., 1996; Marianovsky et al., 2001): (1) MazF is a toxin and MazE is an antitoxin that antagonizes MazF; (2) MazF is long-lived, whereas MazE is a labile protein degraded in vivo by the ATP-dependent ClpPA serine protease; (3) MazE and MazF interact; (4) MazE and MazF are co-expressed; and (5) mazEF is negatively autoregulated at the transcriptional level by the combined action of both MazE and MazF proteins on the mazEF promoter P2. Given these properties of mazEF, and the requirement for the continuous expression of MazE to prevent cell death, a model for mazEF-mediated PCD in response to severe nutrient starvation was proposed (Aizenman et al., 1996). Subsequently, this model was broadened to include various other stressful conditions (Sat et al., 2001; Hazan et al., 2001; Sat et al., 2003; Hazan et al., 2004). Under such conditions, mazEF coexpression is inhibited (see below). Because MazE is a labile protein, its cellular concentration drops more rapidly than that of MazF, leaving MazF to exert its toxic effect, leading to cell death (Fig. 1).

  Fig. 1.
  • Download figure
  • Open in new tab
  • Download powerpoint
Fig. 1.

A schematic representation of the E. coli mazEF-mediated cell death pathway (for details, see text).

Several experiments support this model by demonstrating that various agents that cause stressful conditions trigger the mazEF PCD system. (1) The artificial overproduction of guanosine 3′,5′-bispyrophosphate (ppGpp) (Aizenman et al., 1996; Engelberg-Kulka et al., 1998), the amino acid starvation signal molecule produced by the RelA protein (Cashel et al., 1996), triggers death; (2) several antibiotics (rifampicin, chloramphenicol and spectinomycin) that are general inhibitors of transcription and/or translation trigger mazEF-mediated death (Sat et al., 2001; Engelberg-Kulka et al., 2002); (3) Doc protein, which is the toxic product of the addiction module phd-doc of plasmid prophage P1 and is a general inhibitor of translation, drives post-segregational killing that requires the E. coli mazEF system (Hazan et al., 2001); (4) mazEF-mediated cell death is triggered by DNA damage caused by thymine starvation (Sat et al., 2003), mitomycin C, nalidixic acid and UV irradiation (Hazan et al., 2004); (5) oxidative stress (H2O2) and high temperature (50°C) also trigger mazEF-mediated death.

Note that most of the antibiotics and stresses considered in these studies have previously been shown to induce bacterial cell death (Rouviere et al., 1995; Ahmad et al., 1998; Davies and Webb, 1998; Storz and Zheng, 2000). The studies described above clearly show that cell death induced by these conditions is dependent on mazEF. In particular, the involvement of mazEF in cell death induced by thymine starvation deserves special attention: it provides a new insight to an old enigma concerning the mechanism underlying the well-known phenomenon thymine-less death (TLD) (reviewed by Engelberg-Kulka et al., 2004).

The mazEF system is thus a stress-induced suicide module. Stressful conditions can affect the continuous expression of MazE by preventing either its transcription and/or its translation. ppGpp inhibits transcription from the mazEF P2 promoter (Aizenman et al., 1996). In addition, some antibiotics that are general inhibitors of transcription and/or translation can also affect MazE expression. For example, rifampicin inhibits the initiation of RNA synthesis through its interaction with the β-subunit of E. coli RNA polymerase (Wherli and Staehelin, 1971; Davies and Webb, 1998), and chloramphenicol and spectinomycin affect ribosomes and are, therefore, general inhibitors of translation (Spahn and Prescott, 1996; Davies and Webb, 1998). Thymine starvation, another stressful condition, provokes DNA damage that involves a unique breaking/twisting of the chromosome into a configuration that defies all the repair/protective mechanisms (Nakayama et al., 1994; Ahmad et al., 1998). Such serious damage to the DNA would be expected to reduce transcription from the mazEF promoter P2 substantially. Indeed, experiments have shown that, under thymine starvation, the activity of the mazEF promoter P2 is drastically reduced (Sat et al., 2003). mazEF-dependent death at high temperatures may also be induced by inhibition of mazEF expression. At such stressful temperatures, the normal transcription factor, σ70, becomes inactivated; σ70 is replaced by periplasmic σE (Raina et al., 1995; Rouviere et al., 1995). Since the promoter recognition sites of σE (Yura et al., 2000) do not exist in mazEF promoter, σE should not initiate the transcription of the mazEF genes.

Modes of action and structures of MazF and RelE

The mechanisms of the actions of the toxins have recently received much attention in studies of E. coli chromosomal toxin-antitoxin systems. Ectopic over-expression of each toxin studied so far (MazF, ChpBK, RelE and YoeB) inhibits translation but not RNA or DNA synthesis (Christensen et al., 2001; Christensen et al., 2003; Christensen et al., 2004; Zhang et al., 2003). The mode of action of RelE was the first to be studied in vivo and in vitro (Pedersen et al., 2003). RelE causes cleavage of mRNA codons in the ribosomal A site. This is highly codon specific, and occurs between the second and third nucleotide (Pedersen et al., 2003) (Fig. 2B). Among stop codons, it exhibits a strong preference for UAG, intermediate for UAA and weak for UGA. Among the sense codons, its preference is for UCG and CAG. Cleavage of mRNA codons at the ribosomal A site now appears to be an intrinsic characteristic of the ribosome during its pausing. Rather than having ribonucleolytic activity, RelE might therefore simply modulate cleavage at the A site (Hayes and Sauer, 2003).

MazF also inhibits translation by cleaving mRNAs at specific sites (Christensen et al., 2003; Zhang et al., 2003; Münoz-Gomez et al., 2004). However, unlike RelE, MazF cleaves mRNAs in a ribosome-independent manner (Zhang et al., 2003). Thus, MazF appears to be a sequence-specific rather than codon-specific endoribonuclease that preferentially cleaves single-stranded mRNAs at ACA sequences. It does not degrade ACA-less mRNA (Suzuki et al., 2005). Zhang et al. (Zhang et al., 2004) have confirmed this mechanism of MazF action by following cleavage of DNA-RNA chimeric substrates containing XACA sequences. They showed that MazF cleaves 5′ or 3′ of the first A residue of the ACA sequence (Fig. 2A). It cleaves phosphodiester bonds at the 5′ side, yielding a free 5′-OH group on the 3′-end cleavage product and a 2′,3′-cyclic phosphate on the 5′-end product. The 2′-OH group of the nucleotide preceding the ACA sequence is essential for MazF cleavage. Thus, though MazF and RNaseA have different sequence specificities, enzymatically they seem to function similarly.

  Fig. 2.
  • Download figure
  • Open in new tab
  • Download powerpoint
Fig. 2.

MazF and RelE actions and structures. (A) E. coli MazF cleaves mRNAs in a sequence-dependent manner (see main text for details). (B) E. coli RelE affects mRNA cleavage, either directly or indirectly, in a ribosome- and codon-dependent manner (see main text for details). (C) The structure of the E. coli MazE-MazF complex: the two MazE molecules are shown in light and dark blue; the four MazF molecules are shown in yellow, green, pink and red. Reproduced with permission from Elsevier (Kamada et al., 2003). (D) The structure of the P. horikoshii RelB-RelE complex: RelE is shown in green and RelB is shown in red. Reproduced with permission from Nat. Struct. Mol. Biol. (Takagi et al., 2005).

The differences in the modes of action of MazF and RelE are probably a result of different structures. The structures of the E.coli mazEF products have now been solved. Loris and colleagues have determined the crystal structure of MazE (Loris et al., 2003; Lah et al., 2003), and Burley and colleagues have determined the crystal structure of the MazE-MazF antitoxin-toxin complex (Kamada et al., 2003). MazE, in its isolated state, consists of a structured N-terminal dimerization domain and an intrinsically unstructured C-terminal MazF-binding domain. Upon forming a complex with MazF, the C-terminal domain of MazE becomes ordered. It forms an extended structure that runs around the surface of MazF. In the crystal, MazE and MazF form a heterohexamer in which a MazE dimer is sandwiched between two MazF dimers (Fig. 2C). Each MazF homodimer has one binding site occupied with MazE; the other binding site remains free. Thus, in principle, it could form longer linear oligomers of alternating MazE and MazF homodimers. Lah and colleagues (Lah et al., 2005) have described a particular conformational adaptability of MazE, which seems to be essential for the specific recognition of MazF and DNA. The latter is a characteristic that is essential for autoregulation of mazEF at the transcriptional level (Marianovsky et al., 2001). Inouye and colleagues (Zhang et al., 2003) have hypothesized that the unstructured C-terminal region of MazE, which is highly negatively charged, might mimic the single-stranded RNA structure, allowing it to bind to a MazF dimer. This would disturb the MazF RNA-binding site and thus block its endoribonuclease activity.

More recently, Kimura and colleagues (Takagi et al., 2005) have determined the crystal structure of the RelB-RelE antitoxin-toxin complex of the hyperthermophilic archaeon Pyrococcus horikoshii. In contrast to the MazE-MazF complex, in which the ratio of the antitoxin-toxin molecules is 1:2, the ratio in the RelB-RelE complex is 1:1. Since two molecules of RelB-RelE complex are bound together in solution, a heterotetrameric structure has been suggested. In the complex, RelE has a simple ellipsoid architecture, composed of three α-helices and a five-stranded β-sheet. In the RelB-RelE complex, RelB is present as a polypeptide chain that lacks any distinct hydrophobic core and wraps around RelE. Like the C-terminal half of MazE, RelB is probably unstructured in isolation.

Most of the RelB chain makes contact with surface residues of RelE (Fig. 2D). However, site-directed mutagenesis indicates that the site predicted to be essential for RelE function does not interact directly with the antitoxin RelB. This is in contrast to nucleases such as barnase, colicin D (Buckle et al., 1994) and probably MazF (see above) that are blocked by their respective inhibitors through direct interactions with the active site of the enzyme. RelB therefore does not appear to prevent RelE from being active, but rather prevents RelE from entering the A site of the ribosome by increasing the size of the complex. It is interesting that the dimensions and shape of RelE are similar to those of domain IV of bacterial elongation factor G (EF-G), which recognizes the ribosomal A site by tRNA mimicry. This suggests that RelE enters the ribosome A site in a way similar to that in which the decoding domain of EF-G interacts with ribosomes (Takagi et al., 2005; Wilson and Nierhaus, 2005). Thus, the particular structure of RelE might contribute to its direct or indirect ribosome-dependent ribonucleolytic action, whereas MazF, which lacks such required properties, acts differently: it is a ribosome-independent ribonuclease.

A point of no return

On the basis of experiments on the mazEF, chpBIK and relBE modules, Pedersen et al. (Pedersen et al., 2002) have suggested that, rather than inducing PCD, chromosomal toxin-antitoxin systems induce a state of reversible bacteriostasis. They showed that ectopic over-expression of MazF or RelE inhibits translation and cell growth, which can resume if the cognate antitoxin is expressed at a later time (Pedersen et al., 2002). However, these experiments were carried out over a short time window, within only five hours of MazF induction (Pedersen et al., 2002). More-recent studies using a similar ectopic over-expression system (Amitai et al., 2004) showed that MazE can indeed resuscitate E. coli cells within six hours of MazF overproduction. But, when this period is extended past six hours, the ability of MazE to resuscitate the cells drastically decreases. Moreover, the inability of MazE to reverse the bacteriocidic effect of MazF is even more dramatic when MazF is over-expressed in cells growing in liquid minimal medium, rather than in rich medium. There is thus a `point of no return', which occurs sooner in minimal medium than in rich medium (Amitai et al., 2004). A point of no return is also reached after the induction of chromosomal mazEF-mediated cell death by various stressful conditions. Again, there is only a short time window during which the ectopic overexpression of MazE can reverse the lethal action of the chromosome-encoded MazF (I. Kolodkin and H.E.-K., unpublished).

  Fig. 3
  • Download figure
  • Open in new tab
  • Download powerpoint
Fig. 3

. A model for the behavior of WT and ΔmazEF cultures during phage P1 attack. (A) In WT cells, mazEF mediates the death of the infected cells. As a consequence, the development of the phage is restricted, the phage titer is low, and the culture survives. (B) In ΔmazEF cultures, nothing interferes with the phage infections: the infected cells lyse and spread infecting particles to the rest of the cells in the culture. Thus, the WT culture can survive phage infections whereas the ΔmazEF culture dies. PCD, programmed cell death.

As described above, MazF cleaves mRNAs (Christensen et al., 2003; Münoz-Gomez et al., 2004; Zhang et al., 2003; Zhang et al., 2004). In addition, MazF also cleaves tmRNA (Christensen et al., 2003), which is a tRNA-mRNA hybrid that can rescue ribosomes by binding to the A site of those containing a truncated mRNA. It then tags the corresponding nascent polypeptide chains with a protein degradation signal, while allowing translation to terminate normally (reviewed by Karzai et al., 2000). MazF-cleaved tmRNA probably cannot rescue ribosomes that are stalled by MazF-cleaved mRNAs; as a result, protein synthesis is inhibited.

Given the point of no return in mazEF-mediated cell death (Amitai et al., 2004), one can envisage a model in which the endoribonucleolytic effect of MazF would be one of the initial steps in the PCD pathway. Such a step could still be reversed by the antagonistic effect of MazE on MazF (Fig. 1). Further cleavage of mRNAs and tmRNA by MazF would be prevented by MazE, and previously truncated mRNAs could be released from the ribosomes through the action of de novo synthesized, uncleaved tmRNA. However, we suggest that MazE cannot reverse downstream events already initiated by MazF. Thus, if the process is not stopped in time, cell death eventually becomes unavoidable. How might the inhibition of translation by MazF induce such a downstream cascade that leads to cell death? It might be because MazF cleaves mRNAs at specific sites (Zhang et al., 2003). The action of MazF could lead to selective synthesis of cell death proteins encoded by mRNAs resistant to cleavage by MazF (Fig. 1). These might not contain the ACA target site or be protected from MazF by some other mechanism. Indeed, mazEF could be part of a PCD network. In such a network, MazF would be a mediator rather than an executioner.

mazEF-mediated cell death as a defense mechanism that prevents the spread of phage infections

The presence of a PCD system on the bacterial chromosome raises an intriguing question: what is the role of such a system in unicellular organisms, as bacteria are traditionally considered to be? For an individual bacterium, PCD is clearly counterproductive, but it becomes effective when simultaneously operated by a group of cells (Engelberg-Kulka and Hazan, 2003). Supporting evidence for the view that bacterial PCD is beneficial for the whole culture rather than individual cells comes from experiments showing that mazEF-mediated death acts as a defense mechanism that prevents the spread of phage P1 (Hazan and Engelberg-Kulka, 2004). P1 phages exist in two forms: (1) virulent particles that develop in the host cells (E. coli) and are released by cell lysis; and (2) lysogenic prophages that replicate like plasmids because of their autonomous origin of replication. These phages encode a repressor that permits them to replicate in the host cells without entering into the lytic phase. If the repressor becomes inactivated, prophages enter into the lytic stage.

Studies of lysogenic E. coli cultures that harbor a heat-inducible dormant P1 phage have examined the effect of the mazEF system on phage growth (Hazan and Engelberg-Kulka, 2004). Upon heat-induction, most cells lacking the mazEF system (ΔmazEF cells) lyse, whereas only a small fraction of the wild-type (WT) cells lyse. The ΔmazEF cultures produce significantly more phages than do the WT cultures. Nevertheless, despite the differences in the levels of lysis and phage production, both mazEF+ (WT) and ΔmazEF cells do not produce colonies upon phage induction. A virulent phage P1 gives similar results. A model involving two separate killing mechanisms has therefore been suggested. The ΔmazEF cells (and a small fraction of the cells of the parental strain) are killed by the release of mature progeny phage particles. However, since most of the WT cells do not lyse, they must be killed by a different mechanism: the mazEF-mediated PCD pathway (Fig. 3A).

To test this model, we have simulated invasion of a non-lysogenic culture by lysogenic cells by mixing lysogenic cultures of WT or ΔmazEF cells with the corresponding non-lysogenic cells. Whereas the ΔmazEF cells are susceptible to infection and are totally lysed (Fig. 3B), the WT culture continues to grow and appears not to be infected by phages released from the induced lysogens (Fig. 3A). Since the phage cannot develop in cells that have already died because of the lethal action of the mazEF module, the infection cannot spread, and only the WT culture is protected from total collapse. Thus, although the E. coli mazEF module causes the death of individual cells, it might protect the culture as a whole by preventing the spread of infective phage (Hazan and Engelberg-Kulka, 2004).

Of course, there are probably additional roles for mazEF-mediated PCD. During the response to severe nutritional stress, the death of a subpopulation would provide food for the surviving cells (Aizenman et al., 1996). This occurs during sporulation of Bacillus subtilis, which has a novel PCD system that differs from mazEF and the other toxin-antitoxin systems (Gonzalez-Pastor et al., 2003; Engelberg-Kulka and Hazan, 2003). mazEF could also act as a guardian of the bacterial chromosome: when other systems fail, mazEF-mediated cell death might preserve genomic stability by causing the elimination of cells carrying genomic defects and mutations from the culture. The mazEF module therefore provides an evolutionary advantage for those bacteria that carry it.

Conclusions and perspectives

The mazEF system represents a form of toxin-antitoxin module that has adapted to respond to various stimuli and execute a cell death program in response to viral infection and several environmental stresses. The MazF endoribonuclease, which cleaves mRNAs at specific sequences, might in fact be a mediator rather than an executioner of PCD. It probably mediates cell death by inducing a pathway downstream of its primary endoribonucleolytic effect, but the details of this await elucidation.

So far, the mazEF toxin-antitoxin system has been studied only in E. coli. However, the system is not unique to E. coli, and systems similar to mazEF have been found on the chromosomes of many other bacteria (Mittenhuber, 1999; Engelberg-Kulka et al., 2002), including the pathogens Mycobacterium tuberculosis, Staphylococcus aureus and Bacillus anthracis (Engelberg-Kulka et al., 2004; Pandey and Gerdes, 2005). Future studies will reveal whether such mazEF-like modules mediate cell death in these pathogenic organisms. Of course, toxin-antitoxin systems unlike mazEF, both in E. coli and in other microorganisms (Pandey and Gerdes, 2005), might also play a role in cell death. Given the differences in the structures and modes of action of MazF and RelE, such systems could operate differently and have different roles in bacterial physiology. The products of mazEF (Engelberg-Kulka et al., 2004) and other bacterial toxin-antitoxin systems could be targets for the development of new antibiotics.

Clearly, a system that causes any given cell to commit suicide is not advantageous to that particular cell. However, death by suicide of an individual cell might be advantageous for the bacterial population as a whole. More and more experimental evidence supports the idea that bacterial cultures have many characteristics of multicellular organisms (Kaiser and Losick, 1993; Swift et al., 1996; Dworkin and Shapiro, 1997; Gray, 1997; Fuqua and Greenberg, 1998; Shapiro, 1998; Miller and Bassler, 2001; Henke and Bassler, 2004). Thus, we suggest that it is important to study the process of bacterial cell death mediated by toxin-antitoxin in relation to the multicellular characteristics of bacterial cultures.

Acknowledgements

We thank F. R. Warshaw-Dadon (Jerusalem, Israel) for her critical reading of the manuscript. We thank the Israel Science Foundation administrated by the Israel Academy of Science and Humanities (grant no. 938/04) for financial support.

  • Accepted August 8, 2005.
  • © The Company of Biologists Limited 2005

References

  1. ↵
    Ahmad, S. I., Kirk, S. H. and Eisenstark, A. (1998). Thymine metabolism and thymineless death in prokaryotes and eukaryotes. Annu. Rev. Microbiol. 52, 591-625.
    OpenUrlCrossRefPubMedWeb of Science
  2. ↵
    Aizenman, E., Engelberg-Kulka, H. and Glaser, G. (1996). An Escherichia coli chromosomal `addiction module' regulated by guanosine-3′5′-bispyrophosphate: a model for programmed bacterial cell death. Proc. Natl. Acad. Sci. USA 93, 6059-6063.
    OpenUrlAbstract/FREE Full Text
  3. ↵
    Amitai, S., Yassin, Y. and Engelberg-Kulka, H. (2004). MazF-mediated cell death in Escherichia coli: a point of no return. J. Bacteriol. 186, 8295-8300.
    OpenUrlAbstract/FREE Full Text
  4. ↵
    Bech, F., Jorgensen, W. S. T., Diderichsen, B. and Karlstrom, O. H. (1985). Sequence of the relB transcription unit from Escherichia coli and identification of the relB gene. EMBO J. 4, 1059-1066.
    OpenUrlPubMedWeb of Science
  5. ↵
    Buckle, A., Schreiber, G. and Fersht, A. (1994). Protein-protein recognition: crystal structural analysis of a barnase-barstar complex at 2.0-Å resolution. Biochemistry 33, 8878-8889.
    OpenUrlCrossRefPubMed
  6. ↵
    Cashel, M., Gentry, D. R., Hernandez, V. Z. and Vinella, D. (1996). The Stringent Response. In Escherichia coli and Salmonella: Cellular and Molecular Biology (ed. F. C. Neidhardt, R. Curtiss III, J. L. Ingraham, E. C. C. Ling, K. B. Low, B. Magasanik, W. R. Reznikoff, M. Riley, M. Schaechter and H. E. Umbarger), pp. 1458-1496. Washington, DC: ASM Press.
  7. Cherny, I. and Gazit, E. (2004). The YefM antitoxin defines a family of natively unfolded proteins: implications as a novel antibacterial target. J. Biol. Chem. 279, 8252-8261.
    OpenUrlAbstract/FREE Full Text
  8. ↵
    Christensen, S. K., Mikkelsen, M., Pedersen, K. and Gerdes, K. (2001). RelE, a global inhibitor of translation, is activated during nutritional stress. Proc. Natl. Acad. Sci. USA 98, 14328-14333.
    OpenUrlAbstract/FREE Full Text
  9. ↵
    Christensen, S. K., Pedersen, K., Hensen, F. G. and Gerdes, K. (2003). Toxin-antitoxin loci as stress-response elements: ChpAK/MazF and ChpBK cleave translated mRNAs and are counteracted by tmRNA. J. Mol. Biol. 332, 809-819.
    OpenUrlCrossRefPubMedWeb of Science
  10. ↵
    Christensen, S. K., Maenhaut-Michel, G., Mine, N., Gottesman, S., Gerdes, K. and Van Melderen, L. (2004). Overproduction of the lon protease triggers inhibition of translation in Escherichia coli: involvement of the yefM-yoeB toxin-antitoxin system. Mol. Microbiol. 51, 1705-1717.
    OpenUrlCrossRefPubMedWeb of Science
  11. ↵
    Couturier, M., Bahassi, E. M. and Van Melderen, L. (1998). Bacterial death by DNA gyrase poisoning. Trends Microbiol. 6, 269-275.
    OpenUrlCrossRefPubMedWeb of Science
  12. ↵
    Davies, J. and Webb, V. (1998). Antibiotics resistance in bacteria. In Emerging Infections (ed. R. M. Krause), pp. 239-273. New York: Academic Press.
  13. ↵
    Dworkin, M. and Shapiro, J. (1997). Bacteria as Multi-Cellular Organisms. New York: Oxford University Press.
  14. ↵
    Engelberg-Kulka, H. and Glaser, G. (1999). Addiction modules and programmed cell death and anti-death in bacterial cultures. Annu. Rev. Microbiol. 53, 43-70.
    OpenUrlCrossRefPubMedWeb of Science
  15. ↵
    Engelberg-Kulka, H. and Hazan, R. (2003). Perspective. Cannibals defy starvation and avoid sporulation. Science 301, 467-468.
    OpenUrlAbstract/FREE Full Text
  16. ↵
    Engelberg-Kulka, H., Reches, M., Narasimhan, S., Schoulaker-Schwarz, R., Klemes, Y., Aizenman, E. and Glaser, G. (1998). rexB bacteriophage λ is an anti cell death gene. Proc. Natl. Acad. Sci. USA 95, 15481-15486.
    OpenUrlAbstract/FREE Full Text
  17. ↵
    Engelberg-Kulka, H., Sat, B. and Hazan, R. (2002). Bacterial programmed cell death and antibiotics. ASM News 67, 617-625.
    OpenUrl
  18. ↵
    Engelberg-Kulka, H., Reches, M., Sat, B., Amitai, S. and Hazan, R. (2004). Bacterial programmed cell death as a target for antibiotics. Trends Microbiol. 12, 66-71.
    OpenUrlCrossRefPubMedWeb of Science
  19. ↵
    Fuqua, C. and Greenberg, E. P. (1998). Cell-to-cell communication in Escherichia coli and Salmonella typhimurium: they may be talking, but who's listening? Proc. Natl. Acad. Sci. USA 95, 6571-6572.
    OpenUrlFREE Full Text
  20. ↵
    Gerdes, K., Christensen, S. K. and Lobner-Olesen, A. (2005). Prokaryotic toxin-antitoxin stress response loci. Nat. Rev. Microbiol. 3, 371-382.
    OpenUrlCrossRefPubMedWeb of Science
  21. ↵
    Gonzalez-Pastor, J. E., Hobbs, E. C. and Losick, R. (2003). Cannibalism by sporulating bactera. Science 301, 510-513.
    OpenUrlAbstract/FREE Full Text
  22. ↵
    Gotfredsen, M. and Gerdes, K. (1998). The Escherichia coli relBE genes belong to a new toxin-antitoxin gene family. Mol. Microbiol. 29, 1065-1076.
    OpenUrlCrossRefPubMedWeb of Science
  23. ↵
    Grady, R. and Hayes, F. (2003). Axe-Txe, a broad-spectrum proteic toxin-antitoxin system specified by a multidrug-resistant clinical isolate of Enterococcus faecium. Mol. Microbiol. 47, 1419-1432.
    OpenUrlCrossRefPubMedWeb of Science
  24. ↵
    Gray, K. M. (1997). Intertcellular communication and group behavior in bacteria. Trends Microbiol. 5, 184-188.
    OpenUrlCrossRefPubMedWeb of Science
  25. ↵
    Hayes, C. S. and Sauer, R. T. (2003). Cleavage of the A site mRNA codon during ribosome pausing provides a mechanism for translational quality control. Mol. Cell 12, 903-911.
    OpenUrlCrossRefPubMedWeb of Science
  26. ↵
    Hayes, F. (2003). Toxins-antitoxins: plasmid maintenance, programmed cell death, and cell cycle arrest. Science 301, 1496-1499.
    OpenUrlAbstract/FREE Full Text
  27. ↵
    Hazan, R. and Engelberg-Kulka, H. (2004). Escherichia coli mazEF mediated cell death as a defense mechanism that prevents spreading of phage P1. Mol. Genet. Genomics 272, 227-234.
    OpenUrlPubMedWeb of Science
  28. ↵
    Hazan, R., Sat, B., Reches, M. and Engelberg-Kulka, H. (2001). The post-segregational killing mediated by the phage P1 `addiction module': phd-doc requires the Escherichia coli programmed cell death system mazEF. J. Bacteriol. 183, 2046-2050.
    OpenUrlAbstract/FREE Full Text
  29. ↵
    Hazan, R., Sat, B. and Engelberg-Kulka, H. (2004). Escherichia coli mazEF mediated cell death is triggered by various stressful conditions. J. Bacteriol. 186, 3663-3669.
    OpenUrlAbstract/FREE Full Text
  30. ↵
    Hengartner, M. O. (2000). The biochemistry of apoptosis. Nature 407, 770-776.
    OpenUrlCrossRefPubMedWeb of Science
  31. ↵
    Henke, J. M. and Bassler, B. L. (2004). Bacterial social engagements. Trends Cell Biol. 14, 648-656.
    OpenUrlCrossRefPubMedWeb of Science
  32. ↵
    Jacobson, M. D., Weil, M. and Raff, M. C. (1997). Programmed cell death in animal development. Cell 88, 347-354.
    OpenUrlCrossRefPubMedWeb of Science
  33. ↵
    Jensen, R. B. and Gerdes, K. (1995). Programmed cell death in bacteria: proteic plasmid stabilization systems. Mol. Microbiol. 17, 205-210.
    OpenUrlCrossRefPubMedWeb of Science
  34. ↵
    Kaiser, D. and Losick, R. (1993). How and why bacteria talk to each other. Cell 73, 873-885.
    OpenUrlCrossRefPubMedWeb of Science
  35. ↵
    Kamada, K., Hanaoka, F. and Burley, S. K. (2003). Crystal structure of the MazE/MazF complex: molecular bases of antidote-toxin recognition. Mol. Cell 11, 875-884.
    OpenUrlCrossRefPubMedWeb of Science
  36. ↵
    Karzai, A. W., Roch, E. D. and Sauer, R. T. (2000). The SsrA-Smp system for protein tagging, directed degradation and ribosome rescue. Nat. Struct. Biol. 7, 449-455.
    OpenUrlCrossRefPubMedWeb of Science
  37. ↵
    Kerr, J. F. R., Wyllie, A. H. and Curie, A. R. (1972). Apoptosis: a basic biological phenomenon with wide-ranging implication in tissue kinetics. Br. J. Cancer 26, 239-257.
    OpenUrlCrossRefPubMedWeb of Science
  38. ↵
    Lah, J., Marianovsky, I., Engelberg-Kulka, H., Glaser, H. and Loris, R. (2003). Interaction of the addiction antidote MazE with dromedary single domain antibody fragment: structure, thermodynamics of binding, stability and influence of DNA recognition. J. Biol. Chem. 278, 14101-14111.
    OpenUrlAbstract/FREE Full Text
  39. ↵
    Lah, J., Simic, M., Vesnaver, G., Marianovsky, I., Glaser, G., Engelberg-Kulka, H. and Loris, R. (2005). Energetics of structural transitions of the addiction antitoxin MazE: is programmed bacterial cell death dependent on the intrinsically flexible nature of the antitoxin? J. Biol. Chem. 280, 17397-17407.
    OpenUrlAbstract/FREE Full Text
  40. ↵
    Loris, R., Marianovsky, I., Lah, J., Laermans, T., Engelberg-Kulka, H., Glaser, G., Muylderman, S. and Wyne, L. (2003). Crystal structure of the intrinsically flexible addiction antidote MazE. J. Biol. Chem. 278, 28252-28257.
    OpenUrlAbstract/FREE Full Text
  41. ↵
    Marianovsky, I., Aizenman, E., Engelberg-Kulka, H. and Glaser, G. (2001). The regulation of the Escherichia coli mazEF promoter involves an unusual alternating palindrome. J. Biol. Chem. 278, 5975-5984.
    OpenUrl
  42. ↵
    Masuda, Y. and Ohtsubo, E. (1994). Mapping and disruption of the chpB locus in Escherichia coli. J. Bacteriol. 176, 5861-5863.
    OpenUrlAbstract/FREE Full Text
  43. ↵
    Masuda, Y., Miyakawa, K., Nishimura, Y. and Ohtsubo, E. (1993). chpA and chpB, Escherichia coli chromosomal homologs of the pem locus responsible for stable maintenance of plasmid R100. J. Bacteriol. 175, 6850-6856.
    OpenUrlAbstract/FREE Full Text
  44. ↵
    Metzger, S., Dror, I. B., Aizenman, E., Schreiber, G., Toone, M., Friesen, J. D., Cashel, M. and Glaser, G. (1988). The nucleotide sequence and characterization of the relA gene of Escherichia coli. J. Biol. Chem. 263, 15699-15704.
    OpenUrlAbstract/FREE Full Text
  45. ↵
    Miller, M. B. and Bassler, B. L. (2001). Quorum sensing in bacteria. Annu. Rev. Microbiol. 55, 165-199.
    OpenUrlCrossRefPubMedWeb of Science
  46. ↵
    Mittenhuber, G. (1999). Occurrence of MazEF-like antitoxin/toxin systems in bacteria. J. Mol. Microbiol. Biothechnol. 1, 295-302.
    OpenUrl
  47. ↵
    Münoz-Gomez, A. G., Santos-Sierra, S., Berzal-Herranz, A., Lemonner, M. and Diaz-Orejas, R. (2004). Insight into the specificity of RNA cleavage by the Escherichia coli MazF toxin. FEBS Lett. 567, 316-320.
    OpenUrlCrossRefPubMedWeb of Science
  48. ↵
    Nagata, A. (1997). Apoptosis by death factor. Cell 88, 355-365.
    OpenUrlCrossRefPubMedWeb of Science
  49. ↵
    Nakayama, K., Kusano, K., Irino, N. and Nakayama, H. (1994). Thymine starvation induced structural changes in Escherichia coli DNA. Detection by pulse field gelelectrophoresis and evidence for involvement of homologous recombination. J. Mol. Biol. 243, 611-620.
    OpenUrlCrossRefPubMedWeb of Science
  50. ↵
    Pandey, D. P. and Gerdes, K. (2005). Toxin-antitoxin loci are highly abandant in free-living but lost from host-associated prokaryotes. Nucleic Acids Res. 33, 966-976.
    OpenUrlAbstract/FREE Full Text
  51. ↵
    Pedersen, K., Christensen, S. K. and Gerdes, K. (2002). Rapid induction and reversal of bacteriostatic conditions by controlled expression of toxins and antitoxins. Mol. Microbiol. 45, 501-510.
    OpenUrlCrossRefPubMedWeb of Science
  52. ↵
    Pedersen, K., Zavialov, K., Pavlov, M. Y., Elf, J., Gerdes, K. and Ehrenberg, M. (2003). The bacterial toxin RelE displays codon-specific cleavage of mRNAs in the ribosomal A site. Cell 112, 131-140.
    OpenUrlCrossRefPubMedWeb of Science
  53. ↵
    Raff, M. (1998). Cell suicide for beginners. Nature 396, 119-122.
    OpenUrlCrossRefPubMedWeb of Science
  54. ↵
    Raina, S., Missiakas, D. and Georgopoulos, D. (1995). The rpoE gene encoding the sigma E (sigma 24) heat shock sigma factor of Escherichia coli. EMBO J. 14, 1043-1055.
    OpenUrlPubMedWeb of Science
  55. ↵
    Rouviere, P. E., De Las Penas, A., Mecsas, J., Lu, C. Z., Rudd, K. E. and Gross, C. A. (1995). rpoE, the gene encoding the second heat-shock sigma factor, sigma E, in Escherichia coli. EMBO J. 14, 1032-1042.
    OpenUrlPubMedWeb of Science
  56. ↵
    Sat, B., Hazan, R., Fisher, T., Khaner, H., Glaser, G. and Engelberg-Kulka, H. (2001). Programmed cell death in Escherichia coli: some antibiotics can trigger the MazEF lethality. J. Bacteriol. 183, 2041-2045.
    OpenUrlAbstract/FREE Full Text
  57. ↵
    Sat, B., Reches, M. and Engelberg-Kulka, H. (2003). The Escherichia coli chromosomal `suicide module' mazEF is involved in thymine-less death. J. Bacteriol. 185, 1803-1807.
    OpenUrlAbstract/FREE Full Text
  58. ↵
    Shapiro, J. A. (1998). Thinking about bacterial populations as multi-cellular organisms. Annu. Rev. Microbiol. 52, 81-104.
    OpenUrlCrossRefPubMedWeb of Science
  59. ↵
    Spahn, C. M. T. and Prescott, C. D. (1996). Throwing a spanner in the works: antibiotics and the translation apparatus. J. Mol. Biol. 74, 423-439.
    OpenUrl
  60. ↵
    Storz, G. and Zheng, M. (2000). Oxidative Stress. In Bacterial Stress Response (ed. G. Storz and R. Hengge-Aronis), pp. 47-59. Washington, DC: ASM Press.
  61. ↵
    Suzuki, M., Zhang, J., Liu, M., Woychik, N. and Inouye, M. (2005). Single protein production in living cells facilitated by an mRNA interferase. Mol. Cell. 18, 253-261.
    OpenUrlCrossRefPubMedWeb of Science
  62. ↵
    Swift, S., Throup, J. P., Williams, P., Salmond, G. P. and Stewart, G. S. (1996). Quorum sensing: a population-density component in the determination of bacterial phenotype. Trends Biochem. Sci. 21, 214-219.
    OpenUrlCrossRefPubMedWeb of Science
  63. ↵
    Takagi, H., Kakjuta, Y., Okada, T., Yao, M., Tanaka, I. and Kimura, M. (2005). Crystal structure of archaeal toxin-antitoxin RelE-RelB complex with implications for toxin activity and antitoxin effects. Nat. Struct. Mol. Biol. 12, 327-331.
    OpenUrlCrossRefPubMedWeb of Science
  64. ↵
    Wherli, W. and Stahelin, M. (1971). Actions of the rifamipicins. Bacteriol. Rev. 35, 290-309.
    OpenUrlFREE Full Text
  65. ↵
    Wilson, D. and Nierhaus, K. H. (2005). RelBE or not to be. Nat. Struct. Mol. Biol. 12, 282-284.
    OpenUrlCrossRefPubMedWeb of Science
  66. ↵
    Yarmolinsky, M. B. (1995). Programmed cell death in bacterial population. Science 267, 836-837.
    OpenUrlFREE Full Text
  67. ↵
    Yura, T., Kanemori, M. and Morita, T. M. (2000). The heat shock response: regulation and function. In Bacterial Stress Response (ed. G. Storz and R. Hengge-Aronis), pp. 3-18. Washington, DC: ASM Press.
  68. ↵
    Zhang, Y., Zhang, J., Hoeflich, K. P., Ikura, M., Quing, G. and Inouye, M. (2003). MazF cleaves cellular mRNA specifically at ACA to block protein synthesis in Escherichia coli. Mol. Cell 12, 913-923.
    OpenUrlCrossRefPubMedWeb of Science
  69. ↵
    Zhang, Y., Zhang, J., Hara, H., Kato, I. and Inouye, M. (2004). Insight into mRNA cleavage mechanism by MazF, an mRNA interferase. J. Biol. Chem. 280, 3143-3150.
    OpenUrlPubMed
View Abstract
Previous ArticleNext Article
Back to top
Previous ArticleNext Article

This Issue

 Download PDF

Email

Thank you for your interest in spreading the word on Journal of Cell Science.

NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address.

Enter multiple addresses on separate lines or separate them with commas.
mazEF: a chromosomal toxin-antitoxin module that triggers programmed cell death in bacteria
(Your Name) has sent you a message from Journal of Cell Science
(Your Name) thought you would like to see the Journal of Cell Science web site.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.
Share
Commentary
mazEF: a chromosomal toxin-antitoxin module that triggers programmed cell death in bacteria
Hanna Engelberg-Kulka, Ronen Hazan, Shahar Amitai
Journal of Cell Science 2005 118: 4327-4332; doi: 10.1242/jcs.02619
del.icio.us logo Digg logo Reddit logo Twitter logo CiteULike logo Facebook logo Google logo Mendeley logo
Citation Tools
Commentary
mazEF: a chromosomal toxin-antitoxin module that triggers programmed cell death in bacteria
Hanna Engelberg-Kulka, Ronen Hazan, Shahar Amitai
Journal of Cell Science 2005 118: 4327-4332; doi: 10.1242/jcs.02619

Citation Manager Formats

  • BibTeX
  • Bookends
  • EasyBib
  • EndNote (tagged)
  • EndNote 8 (xml)
  • Medlars
  • Mendeley
  • Papers
  • RefWorks Tagged
  • Ref Manager
  • RIS
  • Zotero
Alerts

Please log in to add an alert for this article.

Sign in to email alerts with your email address

Article navigation

  • Top
  • Article
    • Summary
    • Introduction
    • mazEF is a stress-induced suicide module
    • Modes of action and structures of MazF and RelE
    • A point of no return
    • mazEF-mediated cell death as a defense mechanism that prevents the spread of phage infections
    • Conclusions and perspectives
    • Acknowledgements
    • References
  • Figures & tables
  • Info & metrics
  • PDF

Related articles

Cited by...

More in this TOC section

  • Lamins in the nuclear interior − life outside the lamina
  • Molecular mechanisms of kinesin-14 motors in spindle assembly and chromosome segregation
  • Mechanisms of regulation and diversification of deubiquitylating enzyme function
Show more Commentary

Similar articles

Other journals from The Company of Biologists

Development

Journal of Experimental Biology

Disease Models & Mechanisms

Biology Open

Advertisement

2020 at The Company of Biologists

Despite the challenges of 2020, we were able to bring a number of long-term projects and new ventures to fruition. While we look forward to a new year, join us as we reflect on the triumphs of the last 12 months.


Mole – The Corona Files

"This is not going to go away, 'like a miracle.' We have to do magic. And I know we can."

Mole continues to offer his wise words to researchers on how to manage during the COVID-19 pandemic.


Cell scientist to watch – Christine Faulkner

In an interview, Christine Faulkner talks about where her interest in plant science began, how she found the transition between Australia and the UK, and shares her thoughts on virtual conferences.


Read & Publish participation extends worldwide

“The clear advantages are rapid and efficient exposure and easy access to my article around the world. I believe it is great to have this publishing option in fast-growing fields in biomedical research.”

Dr Jaceques Behmoaras (Imperial College London) shares his experience of publishing Open Access as part of our growing Read & Publish initiative. We now have over 60 institutions in 12 countries taking part – find out more and view our full list of participating institutions.


JCS and COVID-19

For more information on measures Journal of Cell Science is taking to support the community during the COVID-19 pandemic, please see here.

If you have any questions or concerns, please do not hestiate to contact the Editorial Office.

Articles

  • Accepted manuscripts
  • Issue in progress
  • Latest complete issue
  • Issue archive
  • Archive by article type
  • Special issues
  • Subject collections
  • Interviews
  • Sign up for alerts

About us

  • About Journal of Cell Science
  • Editors and Board
  • Editor biographies
  • Travelling Fellowships
  • Grants and funding
  • Journal Meetings
  • Workshops
  • The Company of Biologists

For Authors

  • Submit a manuscript
  • Aims and scope
  • Presubmission enquiries
  • Fast-track manuscripts
  • Article types
  • Manuscript preparation
  • Cover suggestions
  • Editorial process
  • Promoting your paper
  • Open Access
  • JCS Prize
  • Manuscript transfer network
  • Biology Open transfer

Journal Info

  • Journal policies
  • Rights and permissions
  • Media policies
  • Reviewer guide
  • Sign up for alerts

Contacts

  • Contact JCS
  • Subscriptions
  • Advertising
  • Feedback

Twitter   YouTube   LinkedIn

© 2021   The Company of Biologists Ltd   Registered Charity 277992