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Journal of Bacteriology, November 2008, p. 7068-7078, Vol. 190, No. 21
0021-9193/08/$08.00+0     doi:10.1128/JB.00712-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

The Mycobacterium tuberculosis phoPR Operon Is Positively Autoregulated in the Virulent Strain H37Rv{triangledown} ,{dagger}

Jesús Gonzalo-Asensio,1,6 Carlos Y. Soto,2 Ainhoa Arbués,1,6 Javier Sancho,3 María del Carmen Menéndez,4 María J. García,4 Brigitte Gicquel,5 and Carlos Martín1,6*

Departamento de Microbiología, Medicina Preventiva y Salud Pública, Universidad de Zaragoza, Zaragoza, Spain,1 Departamento de Química, Facultad de Ciencias, Universidad Nacional de Colombia, Bogotá, Colombia,2 Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, and Institute for Biocomputation and Physics of Complex Systems (BIFI), Universidad de Zaragoza, Zaragoza, Spain,3 Departamento de Medicina Preventiva, Universidad Autónoma de Madrid, Madrid, Spain,4 Unité Génétique Mycobactérienne, Institut Pasteur, Paris, France,5 CIBER Enfermedades Respiratorias, Mallorca, Spain6

Received 21 May 2008/ Accepted 16 August 2008

The attenuated Mycobacterium tuberculosis H37Ra strain is an isogenic counterpart of the virulent paradigm strain H37Rv. Recently, a link between a point mutation in the PhoP transcriptional regulator and avirulence of H37Ra was established. Remarkably, a previous study demonstrated negative autoregulation of the phoP gene in H37Ra. These findings led us to study the transcriptional autoregulation of PhoP in the virulent H37Rv strain. In contrast to the negative autoregulation of PhoP previously published for H37Ra, our experiments using a phoP promoter-lacZ fusion showed that PhoP is positively autoregulated in both H37Rv and H37Ra compared with an H37Rv phoP deletion mutant constructed in this study. Using quantitative reverse transcription-PCR (RT-PCR) analysis, we showed that the phoP gene is transcribed at similar levels in H37Rv and H37Ra. Gel mobility shift and DNase I footprinting assays allowed us to identify the precise binding region of PhoP from H37Rv to the phoP promoter. We also carried out RT-PCR studies to demonstrate that phoP is transcribed together with the adjacent gene phoR, which codes for the cognate histidine kinase of the phoPR two-component system. In addition, quantitative RT-PCR studies showed that phoR is independently transcribed from a promoter possibly regulated by PhoP. Finally, we discuss the possible role in virulence of a single point mutation found in the phoP gene from the attenuated H37Ra strain but not in virulent members of the M. tuberculosis complex.

* Corresponding author. Mailing address: Departamento de Microbiología, Medicina Preventiva y Salud Pública, Facultad de Medicina, Universidad de Zaragoza, C/Domingo Miral s/n, 50009 Zaragoza, Spain. Phone: 34 976 76 17 59. Fax: 34 976 76 16 64. E-mail: carlos{at}unizar.es

{triangledown} Published ahead of print on 29 August 2008.

{dagger} Supplemental material for this article may be found at http://jb.asm.org/.

Journal of Bacteriology, November 2008, p. 7068-7078, Vol. 190, No. 21
0021-9193/08/$08.00+0     doi:10.1128/JB.00712-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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