Abstract
MqsA, the antitoxin of the MqsR/MqsA toxin/antitoxin (TA) system, is a global regulator that reduces expression of several stress response genes (e.g., mqsRA, cspD, and rpoS) by binding to the promoter palindromic motif [5′-AACCT (N)3 AGGTT-3′]. We identified a similar mqsRA-like palindrome [5′-AACCT TA AGGTT-3′] 78 bp upstream of the transcription initiation site in the csgD promoter (p-csgD). CsgD is a master regulator for biofilm formation via its control of curli and cellulose production. We show here that MqsA binds to this palindrome in p-csgD to repress csgD transcription. As expected, p-csgD repression by MqsA resulted in reduced transcription from CsgD-regulated curli genes csgA and csgB (encoding the major and minor curlin subunits, respectively). Curli production was reduced in colonies and in planktonic cells upon MqsA production. Hence, MqsA directly represses p-csgD, and thereby influences curli formation. This demonstrates that TA systems can impact overall cell physiology by fine-tuning cellular stress responses.
Highlights
MqsA, the antitoxin of the MqsR/MqsA toxin/antitoxin (TA) system, is a global regulator that reduces expression of several stress response genes by binding to the promoter palindromic motif [59-AACCT (N)[3] AGGTT-39]
We have shown that MqsA is a global regulator that represses rpoS transcription by binding at the mqsRA-like palindrome of p-rpoS31
In the presence of oxidative stress, which would normally induce genes positively controlled by RpoS such as those encoding curli, curli/cellulose production was reduced by 13 6 2 fold in cells producing MqsA, and the csgD transcript was decreased by 3 6 1 fold[31]
Summary
MqsA, the antitoxin of the MqsR/MqsA toxin/antitoxin (TA) system, is a global regulator that reduces expression of several stress response genes (e.g., mqsRA, cspD, and rpoS) by binding to the promoter palindromic motif [59-AACCT (N)[3] AGGTT-39]. MqsA possesses a C-terminal helix-turn-helix domain[32] that allows www.nature.com/scientificreports direct binding to a specific palindromic DNA motif [59-AACCT (N)[3] AGGTT-39] found in two copies in the promoter region of mqsRA33. Upon binding to this palindrome through its C-terminal domain, MqsA controls expression of various genes such as mqsRA33, rpoS31, and cspD34. MqsA behaves as a negative determinant in biofilm formation and as a regulator of an important regulator (CsgD)
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