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CroS_R391 , an ortholog of the λ Cro repressor, plays a major role in suppressing polV_R391 -dependent mutagenesis.

ABSTRACT: When subcloned into low-copy-number expression vectors, rumAB, encoding polV_R391 (RumA'₂ B), is best characterized as a potent mutator giving rise to high levels of spontaneous mutagenesis in vivo. This is in dramatic contrast to the poorly mutable phenotype when polV_R391 is expressed from the native 88.5 kb R391, suggesting that R391 expresses cis-acting factors that suppress the expression and/or the activity of polV_R391 . Indeed, we recently discovered that SetR_R391 , an ortholog of λ cI repressor, is a transcriptional repressor of rumAB. Here, we report that CroS_R391 , an ortholog of λ Cro, also serves as a potent transcriptional repressor of rumAB. Levels of RumA are dependent upon an interplay between SetR_R391 and CroS_R391 , with the greatest reduction of RumA protein levels observed in the absence of SetR_R391 and the presence of CroS_R391 . Under these conditions, CroS_R391 completely abolishes the high levels of mutagenesis promoted by polV_R391 expressed from low-copy-number plasmids. Furthermore, deletion of croS_R391 on the native R391 results in a dramatic increase in mutagenesis, indicating that CroS_R391 plays a major role in suppressing polV_R391 mutagenesis in vivo. Inactivating mutations in CroS_R391 therefore have the distinct possibility of increasing cellular mutagenesis that could lead to the evolution of antibiotic resistance of pathogenic bacteria harboring R391.

SUBMITTER: McDonald JP

PROVIDER: S-EPMC8460599 | biostudies-literature | 2021 Sep

REPOSITORIES: biostudies-literature

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CroSR391 , an ortholog of the λ Cro repressor, plays a major role in suppressing polVR391 -dependent mutagenesis.

McDonald John P JP Quiros Dominic R DR Vaisman Alexandra A Mendez Antonio R AR Reyelt Jan J Schmidt Marlen M Gonzalez Martín M Woodgate Roger R

Molecular microbiology 20210712 3

When subcloned into low-copy-number expression vectors, rumAB, encoding polVR391 (RumA'2 B), is best characterized as a potent mutator giving rise to high levels of spontaneous mutagenesis in vivo. This is in dramatic contrast to the poorly mutable phenotype when polVR391 is expressed from the native 88.5 kb R391, suggesting that R391 expresses cis-acting factors that suppress the expression and/or the activity of polVR391 . Indeed, we recently discove ...[more]

PMID: 34184328

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Project description:UnlabelledIntegrative and conjugative elements (ICEs) of the SXT/R391 family are the main contributors to acquired multidrug resistance in the seventh pandemic lineage of Vibrio cholerae, the etiological agent of the diarrheal disease cholera. Conjugative transfer of SXT/R391 ICEs is triggered by antibiotics and agents promoting DNA damage through RecA-dependent autoproteolysis of SetR, an ICE-encoded λ CI-like repressor. Here, we describe the role of CroS, a distant λ Cro homolog, as a key component contributing to the regulation of expression of the activator SetCD that orchestrates the expression of the conjugative transfer genes. We show that deletion of croS abolishes the SOS response-dependent induction of SXT despite the presence of a functional setR gene. Using quantitative reverse transcription-PCR and lacZ reporter assays, we also show that CroS represses setR and setCD expression by binding to operator sites shared with SetR. Furthermore, we provide evidence of an additional operator site bound by SetR and CroS. Finally, we show that SetCD expression generates a positive feedback loop due to SXT excision and replication in a fraction of the cell population. Together, these results refine our understanding of the genetic regulation governing the propagation of major vectors of multidrug resistance.ImportanceHealthcare systems worldwide are challenged by an alarming drug resistance crisis caused by the massive and rapid propagation of antibiotic resistance genes and the associated emergence of multidrug-resistant pathogenic bacteria. SXT/R391 ICEs contribute to this phenomenon not only in clinical and environmental vibrios but also in several members of the family Enterobacteriaceae. We have identified and characterized here the regulator CroS as a key factor in the stimulation of conjugative transfer of these ICEs in response to DNA-damaging agents. We have also untangled conflicting evidence regarding autoactivation of transfer by the master activator of SXT/R391 ICEs, SetCD. Discovery of CroS provides a clearer and more complete understanding of the regulatory network that governs the dissemination of SXT/R391 ICEs in bacterial populations.

Dataset Information

CroS_R391 , an ortholog of the λ Cro repressor, plays a major role in suppressing polV_R391 -dependent mutagenesis.

Publications

CroS<sub>R391</sub> , an ortholog of the λ Cro repressor, plays a major role in suppressing polV<sub>R391</sub> -dependent mutagenesis.

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OmicsDI is part of the ELIXIR infrastructure

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Dataset Information

CroSR391 , an ortholog of the λ Cro repressor, plays a major role in suppressing polVR391 -dependent mutagenesis.

Publications

CroS&lt;sub&gt;R391&lt;/sub&gt; , an ortholog of the λ Cro repressor, plays a major role in suppressing polV&lt;sub&gt;R391&lt;/sub&gt; -dependent mutagenesis.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

CroS_R391 , an ortholog of the λ Cro repressor, plays a major role in suppressing polV_R391 -dependent mutagenesis.

CroS<sub>R391</sub> , an ortholog of the λ Cro repressor, plays a major role in suppressing polV<sub>R391</sub> -dependent mutagenesis.