<named-content content-type="genus-species">Vibrio cholerae</named-content> CsrA Directly Regulates <italic toggle="yes">varA</italic> To Increase Expression of the Three Nonredundant Csr Small RNAs

ABSTRACT CsrA, an RNA-binding global regulator, is an essential protein in Vibrio cholerae. V. cholerae CsrA is regulated by three small RNAs (sRNAs), namely, CsrB, CsrC, and CsrD, which act to sequester and antagonize the activity of CsrA. Although the sRNAs were considered to be largely redundant,...

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Autores principales:	Heidi A. Butz, Alexandra R. Mey, Ashley L. Ciosek, Shelley M. Payne
Formato:	article
Lenguaje:	EN
Publicado:	American Society for Microbiology 2019
Materias:	CsrA CsrB ToxR VarA Vibrio cholerae sRNA Microbiology QR1-502
Acceso en línea:	https://doaj.org/article/07ac550dc84643b09d924da31fb3fe30
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spelling	oai:doaj.org-article:07ac550dc84643b09d924da31fb3fe302021-11-15T15:55:24Z<named-content content-type="genus-species">Vibrio cholerae</named-content> CsrA Directly Regulates <italic toggle="yes">varA</italic> To Increase Expression of the Three Nonredundant Csr Small RNAs10.1128/mBio.01042-192150-7511https://doaj.org/article/07ac550dc84643b09d924da31fb3fe302019-06-01T00:00:00Zhttps://journals.asm.org/doi/10.1128/mBio.01042-19https://doaj.org/toc/2150-7511ABSTRACT CsrA, an RNA-binding global regulator, is an essential protein in Vibrio cholerae. V. cholerae CsrA is regulated by three small RNAs (sRNAs), namely, CsrB, CsrC, and CsrD, which act to sequester and antagonize the activity of CsrA. Although the sRNAs were considered to be largely redundant, we found that they differ in expression, half-life, and the ability to regulate CsrA. Further, we identified a feedback loop in the Csr system in which CsrA increases the synthesis of these antagonistic sRNAs. Because the Csr sRNAs are positively regulated by VarA, we determined the effects of CsrA on VarA levels. The level of VarA was reduced in a csrA mutant, and we found that CsrA directly bound to varA mRNA in an electrophoretic mobility shift assay in vitro and in an CsrA-RNA immunoprecipitation assay in vivo. Thus, varA mRNA is an in vivo-verified direct target of CsrA in V. cholerae, and this is the first demonstration of CsrA directly binding to a varA/uvrY/gacA homolog. Additionally, we demonstrated that a varA translational fusion was less active in a csrA mutant than in wild-type V. cholerae, suggesting that CsrA enhances varA translation. We propose that this autoregulatory feedback loop, in which CsrA increases the production of the nonredundant Csr sRNAs by regulating the amount of VarA, provides a mechanism for fine-tuning the availability of CsrA and, thus, of its downstream targets. IMPORTANCE Vibrio cholerae is a major human pathogen, causing epidemics and pandemics of cholera. V. cholerae persists in the aquatic environment, providing a constant source for human infection. Success in transitioning from the environment to the human host and back requires the bacterium to rapidly respond and to adjust its gene expression and metabolism to these two very different habitats. Our findings show that CsrA, an RNA-binding regulatory protein, plays a central role in regulating these transitions. CsrA activity is controlled by the antagonistic sRNAs CsrB, CsrC, and CsrD, and these sRNAs respond to changes in the availability of nutrients. CsrA autoregulates its own activity by controlling these sRNAs via their primary regulator VarA. Thus, the change in CsrA availability in response to nutrient availability allows V. cholerae to alter gene expression in response to environmental cues.Heidi A. ButzAlexandra R. MeyAshley L. CiosekShelley M. PayneAmerican Society for MicrobiologyarticleCsrACsrBToxRVarAVibrio choleraesRNAMicrobiologyQR1-502ENmBio, Vol 10, Iss 3 (2019)
institution	DOAJ
collection	DOAJ
language	EN
topic	CsrA CsrB ToxR VarA Vibrio cholerae sRNA Microbiology QR1-502
spellingShingle	CsrA CsrB ToxR VarA Vibrio cholerae sRNA Microbiology QR1-502 Heidi A. Butz Alexandra R. Mey Ashley L. Ciosek Shelley M. Payne <named-content content-type="genus-species">Vibrio cholerae</named-content> CsrA Directly Regulates <italic toggle="yes">varA</italic> To Increase Expression of the Three Nonredundant Csr Small RNAs
description	ABSTRACT CsrA, an RNA-binding global regulator, is an essential protein in Vibrio cholerae. V. cholerae CsrA is regulated by three small RNAs (sRNAs), namely, CsrB, CsrC, and CsrD, which act to sequester and antagonize the activity of CsrA. Although the sRNAs were considered to be largely redundant, we found that they differ in expression, half-life, and the ability to regulate CsrA. Further, we identified a feedback loop in the Csr system in which CsrA increases the synthesis of these antagonistic sRNAs. Because the Csr sRNAs are positively regulated by VarA, we determined the effects of CsrA on VarA levels. The level of VarA was reduced in a csrA mutant, and we found that CsrA directly bound to varA mRNA in an electrophoretic mobility shift assay in vitro and in an CsrA-RNA immunoprecipitation assay in vivo. Thus, varA mRNA is an in vivo-verified direct target of CsrA in V. cholerae, and this is the first demonstration of CsrA directly binding to a varA/uvrY/gacA homolog. Additionally, we demonstrated that a varA translational fusion was less active in a csrA mutant than in wild-type V. cholerae, suggesting that CsrA enhances varA translation. We propose that this autoregulatory feedback loop, in which CsrA increases the production of the nonredundant Csr sRNAs by regulating the amount of VarA, provides a mechanism for fine-tuning the availability of CsrA and, thus, of its downstream targets. IMPORTANCE Vibrio cholerae is a major human pathogen, causing epidemics and pandemics of cholera. V. cholerae persists in the aquatic environment, providing a constant source for human infection. Success in transitioning from the environment to the human host and back requires the bacterium to rapidly respond and to adjust its gene expression and metabolism to these two very different habitats. Our findings show that CsrA, an RNA-binding regulatory protein, plays a central role in regulating these transitions. CsrA activity is controlled by the antagonistic sRNAs CsrB, CsrC, and CsrD, and these sRNAs respond to changes in the availability of nutrients. CsrA autoregulates its own activity by controlling these sRNAs via their primary regulator VarA. Thus, the change in CsrA availability in response to nutrient availability allows V. cholerae to alter gene expression in response to environmental cues.
format	article
author	Heidi A. Butz Alexandra R. Mey Ashley L. Ciosek Shelley M. Payne
author_facet	Heidi A. Butz Alexandra R. Mey Ashley L. Ciosek Shelley M. Payne
author_sort	Heidi A. Butz
title	<named-content content-type="genus-species">Vibrio cholerae</named-content> CsrA Directly Regulates <italic toggle="yes">varA</italic> To Increase Expression of the Three Nonredundant Csr Small RNAs
title_short	<named-content content-type="genus-species">Vibrio cholerae</named-content> CsrA Directly Regulates <italic toggle="yes">varA</italic> To Increase Expression of the Three Nonredundant Csr Small RNAs
title_full	<named-content content-type="genus-species">Vibrio cholerae</named-content> CsrA Directly Regulates <italic toggle="yes">varA</italic> To Increase Expression of the Three Nonredundant Csr Small RNAs
title_fullStr	<named-content content-type="genus-species">Vibrio cholerae</named-content> CsrA Directly Regulates <italic toggle="yes">varA</italic> To Increase Expression of the Three Nonredundant Csr Small RNAs
title_full_unstemmed	<named-content content-type="genus-species">Vibrio cholerae</named-content> CsrA Directly Regulates <italic toggle="yes">varA</italic> To Increase Expression of the Three Nonredundant Csr Small RNAs
title_sort	<named-content content-type="genus-species">vibrio cholerae</named-content> csra directly regulates <italic toggle="yes">vara</italic> to increase expression of the three nonredundant csr small rnas
publisher	American Society for Microbiology
publishDate	2019
url	https://doaj.org/article/07ac550dc84643b09d924da31fb3fe30
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<named-content content-type="genus-species">Vibrio cholerae</named-content> CsrA Directly Regulates <italic toggle="yes">varA</italic> To Increase Expression of the Three Nonredundant Csr Small RNAs

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