Journal of Bacteriology, August 2005, p. 5691-5699, Vol. 187, No. 16
0021-9193/05/$08.00+0 doi:10.1128/JB.187.16.5691-5699.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Regulation of finP Transcription by DNA Adenine Methylation in the Virulence Plasmid of Salmonella enterica
Eva M. Camacho,1
Ana Serna,1
Cristina Madrid,2
Silvia Marqués,1,
Raúl Fernández,3
Fernando de la Cruz,3
Antonio Juárez,2,
and
Josep Casadesús1*
Departamento de Genética, Universidad de Sevilla, Apartado 1095, Seville 41080,1
Departament de Microbiologia, Universitat de Barcelona, Avda. Diagonal 645, Barcelona 08028,2
Departamento de Biología Molecular, Universidad de Cantabria, Avda. Cardenal Herrera Oria s/n, Santander 39011, Spain3
Received 23 March 2005/
Accepted 16 May 2005
DNA adenine methylase (Dam) mutants of Salmonella enterica serovar Typhimurium contain reduced levels of FinP RNA encoded on the virulence plasmid. Dam methylation appears to regulate finP transcription, rather than FinP RNA stability or turnover. The finP promoter includes canonical 10 and 35 modules and depends on the
70 factor. Regulation of finP transcription by Dam methylation does not require DNA sequences upstream from the 35 module, indicating that Dam acts at the promoter itself or downstream. Unexpectedly, a GATC site overlapping with the 10 module is likewise dispensable for Dam-mediated regulation. These observations indicate that Dam methylation regulates finP transcription indirectly and suggest the involvement of a host factor(s) responsive to the Dam methylation state of the cell. We provide evidence that one such factor is the nucleoid protein H-NS, which acts as a repressor of finP transcription in a Dam background. H-NS also restrains transcription of the overlapping traJ gene, albeit in a Dam-independent fashion. Hence, the decreased FinP RNA content found in Dam hosts of S. enterica appears to result from H-NS-mediated repression of finP transcription.
* Corresponding author. Mailing address: Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Apartado 1095, E-41080 Sevilla, Spain. Phone: 34 95 455 7105. Fax: 34 95 455 7104. E-mail: casadesus{at}us.es.
Present address: Estación Experimental del Zaidín, C. S. I. C., Profesor Albareda 1, Granada 18008, Spain.
Supplemental material for this article may be found at http://jb.asm.org/.
Journal of Bacteriology, August 2005, p. 5691-5699, Vol. 187, No. 16
0021-9193/05/$08.00+0 doi:10.1128/JB.187.16.5691-5699.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
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Copyright © 2005 by the American Society for Microbiology. All rights reserved.