Escherichia coli dinJ-yafQgenes act as a toxin-antitoxin module

Abstract

Bacterial toxin-antitoxin (TA) systems are operons that code for a stable toxic protein and a labile antitoxin. TA modules are widespread on the chromosomes of free-living Bacteria and Archaea, where they presumably act as stress response elements. The chromosome of Escherichia coli K-12 encodes four known TA pairs, as well as the dinJ-yafQ operon, which is hypothesized to be a TA module based on operon organization similar to known TA genes. Induction of YafQ inhibited cell growth, but its toxicity was counteracted by coexpression of dinJ cloned on a separate plasmid. YafQ(His)(6) and DinJ proteins coeluted in Ni(2+)-affinity and gel filtration chromatography, implying the formation of a specific and stable YafQ-DinJ protein complex with an estimated molecular mass of c. 37.3 kDa. Induction of YafQ reduced protein synthesis up to 40% as judged by incorporation of [(35)S]-methionine, but did not influence the rates of DNA and RNA synthesis. Structure modelling of E. coli YafQ revealed its structural relationship with bacterial toxins of known structure suggesting that it might act as a sequence-specific mRNA endoribonuclease.

Functional Identification of Toxin-Antitoxin Molecules from Helicobacter pylori 26695 and Structural Elucidation of the Molecular Interactions

“…In contrast, the antitoxins in the RelE-RelB (n ϭ 2), aRelE-aRelB (n ϭ 2), YoeBYefM (n ϭ 1), and MazF-MazE (n ϭ 4) complexes form dimers (toxin n -antitoxin 2 (7,12,21,38)). It has been suggested that the YafQ-DinJ complex comprises two toxin and two antitoxin molecules (39). Dimerization of antitoxins can be related to observations showing that the antitoxins regulate the TA operon by interacting with DNA as homodimers (7,38,40,41).…”

Characterization of Escherichia coli dinJ-yafQ Toxin-Antitoxin System Using Insights from Mutagenesis Data

“…(His) 6 DinJ-YafQ protein complex was obtained after overexpression of pRSETdinJyafQ plasmid (Table 1) in BL21 strain, and (His) 6 DinJ protein was purified from (His) 6 DinJ-YafQ protein complex as described earlier (33). RNA cleavage analysis in vitro.…”

“…We have shown earlier that E. coli YafQ toxin exhibits high structural similarity to RelE family of toxin RNases such as E. coli YoeB and Pyrococcus horikoshii RelE (33). More recently, Prysak et al (42) demonstrated that YafQ specifically cleaves E. coli mRNA's exclusively at AAA (Lys) codons in the ribosome.…”

“…Further insights into biological role of chromosomal TA systems showed their involvement in persistence, biofilm formation and multidrug tolerance (20,27,30,47,53,55). Escherichia coli K-12 chromosome codes for at least 19 type II TA systems (57), including mazEF, relBE, yefM-yoeB, dinJ-yafQ, prlF-yhaV, chpBI-chpBK, hicAB, yafNO, hipBA, mqsAR, ygjNM, and ygiUT (3,9,15,16,23,31,33,46). Nearly all E. coli chromosome-borne type II TA system toxins investigated to date inhibit translation.…”

The C-Terminal Portion of an Archaeal Toxin, aRelE, Plays a Crucial Role in Protein Synthesis Inhibition

“…6,7) The Escherichia coli chromosome encodes at least five TA systems, RelB-RelE, MazE-MazF, ChpBIChpBK, YefM-YoeB, and DinJ-YafQ. 8) Toxins MazF, ChpBK, YoeB, and YafQ have been found to have intrinsic RNase activity in vitro; they are hence referred to as mRNA interferases. 9) However, a recent study found that mRNA cleavage by YoeB and YafQ was strictly dependent on translation of the mRNA in vivo, whereas site-specific mRNA cleavage by MazF occurred independently of translation in vivo.…”