Extracytoplasmic function (ECF) sigma factor σF is involved in Caulobacter crescentus response to heavy metal stress

Christian Kohler; Rogério F Lourenço; Gabriela Mol Avelar; Suely L Gomes

doi:10.1186/1471-2180-12-210

Extracytoplasmic function (ECF) sigma factor σF is involved in Caulobacter crescentus response to heavy metal stress

Christian Kohler, Rogério F Lourenço, Gabriela Mol Avelar, Suely L Gomes

Medical Sciences

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Abstract

BACKGROUND: The α-proteobacterium Caulobacter crescentus inhabits low-nutrient environments and can tolerate certain levels of heavy metals in these sites. It has been reported that C. crescentus responds to exposure to various heavy metals by altering the expression of a large number of genes.

RESULTS: In this work, we show that the ECF sigma factor σF is one of the regulatory proteins involved in the control of the transcriptional response to chromium and cadmium. Microarray experiments indicate that σF controls eight genes during chromium stress, most of which were previously described as induced by heavy metals. Surprisingly, σF itself is not strongly auto-regulated under metal stress conditions. Interestingly, σF-dependent genes are not induced in the presence of agents that generate reactive oxygen species. Promoter analyses revealed that a conserved σF-dependent sequence is located upstream of all genes of the σF regulon. In addition, we show that the second gene in the sigF operon acts as a negative regulator of σF function, and the encoded protein has been named NrsF (Negative regulator of sigma F). Substitution of two conserved cysteine residues (C131 and C181) in NrsF affects its ability to maintain the expression of σF-dependent genes at basal levels. Furthermore, we show that σF is released into the cytoplasm during chromium stress and in cells carrying point mutations in both conserved cysteines of the protein NrsF.

CONCLUSION: A possible mechanism for induction of the σF-dependent genes by chromium and cadmium is the inactivation of the putative anti-sigma factor NrsF, leading to the release of σF to bind RNA polymerase core and drive transcription of its regulon.

Original language	English
Article number	210
Number of pages	14
Journal	BioMed Central Microbiology
Volume	12
DOIs	https://doi.org/10.1186/1471-2180-12-210
Publication status	Published - 2012

Bibliographical note

Acknowledgements
This work was supported by a grant to S.L.G. from Fundação de Amparo à
Pesquisa do Estado de São Paulo (FAPESP). R.F.L. and C.K. were postdoctoral
fellows from FAPESP, G.M.A. is a pre-doctoral fellow of FAPESP, and S.L.G.
was partially supported by Conselho Nacional de Desenvolvimento Científico
e Tecnológico (CNPq-Brazil). We thank Michael T. Laub for assistance with
the microarray analysis, Cristina E. Alvarez-Martinez for important discussions
and construct pCM30, Chuck S. Farah for careful reading of the manuscript,
and Anne Kohler, Luci D. Navarro and Sandra M. Fernandes for expert
technical assistance.

Keywords

Cadmium
Caulobacter crescentus
Chromium
Gene Expression Profiling
Gene Expression Regulation, Bacterial
Metals, Heavy
Microarray Analysis
Operon
Sigma Factor
Stress, Physiological

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Extracytoplasmic function (ECF) sigma factor σF is involved in Caulobacter crescentus response to heavy metal stress
© 2012 Kohler et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Final published version, 1.04 MBLicence: CC BY

Cite this

@article{1781d319d5244ed9ad30af7f990a1dae,

title = "Extracytoplasmic function (ECF) sigma factor σF is involved in Caulobacter crescentus response to heavy metal stress",

abstract = "BACKGROUND: The α-proteobacterium Caulobacter crescentus inhabits low-nutrient environments and can tolerate certain levels of heavy metals in these sites. It has been reported that C. crescentus responds to exposure to various heavy metals by altering the expression of a large number of genes.RESULTS: In this work, we show that the ECF sigma factor σF is one of the regulatory proteins involved in the control of the transcriptional response to chromium and cadmium. Microarray experiments indicate that σF controls eight genes during chromium stress, most of which were previously described as induced by heavy metals. Surprisingly, σF itself is not strongly auto-regulated under metal stress conditions. Interestingly, σF-dependent genes are not induced in the presence of agents that generate reactive oxygen species. Promoter analyses revealed that a conserved σF-dependent sequence is located upstream of all genes of the σF regulon. In addition, we show that the second gene in the sigF operon acts as a negative regulator of σF function, and the encoded protein has been named NrsF (Negative regulator of sigma F). Substitution of two conserved cysteine residues (C131 and C181) in NrsF affects its ability to maintain the expression of σF-dependent genes at basal levels. Furthermore, we show that σF is released into the cytoplasm during chromium stress and in cells carrying point mutations in both conserved cysteines of the protein NrsF.CONCLUSION: A possible mechanism for induction of the σF-dependent genes by chromium and cadmium is the inactivation of the putative anti-sigma factor NrsF, leading to the release of σF to bind RNA polymerase core and drive transcription of its regulon.",

keywords = "Cadmium, Caulobacter crescentus, Chromium, Gene Expression Profiling, Gene Expression Regulation, Bacterial, Metals, Heavy, Microarray Analysis, Operon, Sigma Factor, Stress, Physiological",

author = "Christian Kohler and Louren{\c c}o, {Rog{\'e}rio F} and {Mol Avelar}, Gabriela and Gomes, {Suely L}",

note = "Acknowledgements This work was supported by a grant to S.L.G. from Funda{\c c}{\~a}o de Amparo {\`a} Pesquisa do Estado de S{\~a}o Paulo (FAPESP). R.F.L. and C.K. were postdoctoral fellows from FAPESP, G.M.A. is a pre-doctoral fellow of FAPESP, and S.L.G. was partially supported by Conselho Nacional de Desenvolvimento Cient{\'i}fico e Tecnol{\'o}gico (CNPq-Brazil). We thank Michael T. Laub for assistance with the microarray analysis, Cristina E. Alvarez-Martinez for important discussions and construct pCM30, Chuck S. Farah for careful reading of the manuscript, and Anne Kohler, Luci D. Navarro and Sandra M. Fernandes for expert technical assistance.",

year = "2012",

doi = "10.1186/1471-2180-12-210",

language = "English",

volume = "12",

journal = "BioMed Central Microbiology",

issn = "1471-2180",

publisher = "BioMed Central",

}

TY - JOUR

T1 - Extracytoplasmic function (ECF) sigma factor σF is involved in Caulobacter crescentus response to heavy metal stress

AU - Kohler, Christian

AU - Lourenço, Rogério F

AU - Mol Avelar, Gabriela

AU - Gomes, Suely L

N1 - Acknowledgements This work was supported by a grant to S.L.G. from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP). R.F.L. and C.K. were postdoctoral fellows from FAPESP, G.M.A. is a pre-doctoral fellow of FAPESP, and S.L.G. was partially supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq-Brazil). We thank Michael T. Laub for assistance with the microarray analysis, Cristina E. Alvarez-Martinez for important discussions and construct pCM30, Chuck S. Farah for careful reading of the manuscript, and Anne Kohler, Luci D. Navarro and Sandra M. Fernandes for expert technical assistance.

PY - 2012

Y1 - 2012

N2 - BACKGROUND: The α-proteobacterium Caulobacter crescentus inhabits low-nutrient environments and can tolerate certain levels of heavy metals in these sites. It has been reported that C. crescentus responds to exposure to various heavy metals by altering the expression of a large number of genes.RESULTS: In this work, we show that the ECF sigma factor σF is one of the regulatory proteins involved in the control of the transcriptional response to chromium and cadmium. Microarray experiments indicate that σF controls eight genes during chromium stress, most of which were previously described as induced by heavy metals. Surprisingly, σF itself is not strongly auto-regulated under metal stress conditions. Interestingly, σF-dependent genes are not induced in the presence of agents that generate reactive oxygen species. Promoter analyses revealed that a conserved σF-dependent sequence is located upstream of all genes of the σF regulon. In addition, we show that the second gene in the sigF operon acts as a negative regulator of σF function, and the encoded protein has been named NrsF (Negative regulator of sigma F). Substitution of two conserved cysteine residues (C131 and C181) in NrsF affects its ability to maintain the expression of σF-dependent genes at basal levels. Furthermore, we show that σF is released into the cytoplasm during chromium stress and in cells carrying point mutations in both conserved cysteines of the protein NrsF.CONCLUSION: A possible mechanism for induction of the σF-dependent genes by chromium and cadmium is the inactivation of the putative anti-sigma factor NrsF, leading to the release of σF to bind RNA polymerase core and drive transcription of its regulon.

AB - BACKGROUND: The α-proteobacterium Caulobacter crescentus inhabits low-nutrient environments and can tolerate certain levels of heavy metals in these sites. It has been reported that C. crescentus responds to exposure to various heavy metals by altering the expression of a large number of genes.RESULTS: In this work, we show that the ECF sigma factor σF is one of the regulatory proteins involved in the control of the transcriptional response to chromium and cadmium. Microarray experiments indicate that σF controls eight genes during chromium stress, most of which were previously described as induced by heavy metals. Surprisingly, σF itself is not strongly auto-regulated under metal stress conditions. Interestingly, σF-dependent genes are not induced in the presence of agents that generate reactive oxygen species. Promoter analyses revealed that a conserved σF-dependent sequence is located upstream of all genes of the σF regulon. In addition, we show that the second gene in the sigF operon acts as a negative regulator of σF function, and the encoded protein has been named NrsF (Negative regulator of sigma F). Substitution of two conserved cysteine residues (C131 and C181) in NrsF affects its ability to maintain the expression of σF-dependent genes at basal levels. Furthermore, we show that σF is released into the cytoplasm during chromium stress and in cells carrying point mutations in both conserved cysteines of the protein NrsF.CONCLUSION: A possible mechanism for induction of the σF-dependent genes by chromium and cadmium is the inactivation of the putative anti-sigma factor NrsF, leading to the release of σF to bind RNA polymerase core and drive transcription of its regulon.

KW - Cadmium

KW - Caulobacter crescentus

KW - Chromium

KW - Gene Expression Profiling

KW - Gene Expression Regulation, Bacterial

KW - Metals, Heavy

KW - Microarray Analysis

KW - Operon

KW - Sigma Factor

KW - Stress, Physiological

U2 - 10.1186/1471-2180-12-210

DO - 10.1186/1471-2180-12-210

M3 - Article

C2 - 22985357

SN - 1471-2180

VL - 12

JO - BioMed Central Microbiology

JF - BioMed Central Microbiology

M1 - 210

ER -

Extracytoplasmic function (ECF) sigma factor σF is involved in Caulobacter crescentus response to heavy metal stress

Abstract

Bibliographical note

Keywords

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