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Infection and Immunity, June 2008, p. 2478-2489, Vol. 76, No. 6
0019-9567/08/$08.00+0     doi:10.1128/IAI.01443-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Expression of the Mycobacterium tuberculosis acr-Coregulated Genes from the DevR (DosR) Regulon Is Controlled by Multiple Levels of Regulation{triangledown} ,{dagger}

Hema M. Vasudeva-Rao1 and Kathleen A. McDonough1,2*

Wadsworth Center, New York State Department of Health,1 Department of Biomedical Sciences, University at Albany, SUNY, Albany, New York2

Received 26 October 2007/ Returned for modification 30 December 2007/ Accepted 10 March 2008

Little is known about how Mycobacterium tuberculosis regulates gene expression in response to its host environment, despite its importance as a pathogen. We previously characterized 10 acr-coregulated genes (ACGs), all of which belong to the DevR (DosR) "dormancy" regulon, and identified one to three copies of a conserved 18-bp palindromic DNA motif in the promoter of each ACG family member. In the present study, we used base substitution analyses to assess the importance of individual motif copies and to identify additional regulatory sequences in five ACG promoters. Regulation of acr, acg, Rv2623, narK2, and Rv1738 was examined by using single-copy M. tuberculosis promoter-lacZ reporter constructs in Mycobacterium bovis BCG under conditions of ambient air versus hypoxia, each in shaking versus standing shallow culture conditions. We found that regulation of these ACG promoters is more heterogeneous than expected and is controlled at multiple levels. In addition to the positive regulation previously associated with DevR (DosR) and the 18-bp ACG motif, we identified negative regulation associated with sequences in the 5' untranslated regions of acg and Rv2623 and positive regulation associated with far upstream regulatory regions of narK2 and Rv1738. The importance of individual ACG motifs varied among the promoters examined, and Rv1738 was exceptional in that its ACG motif copies were associated with negative, rather than positive, regulation under some conditions. Further understanding of this important regulon requires the identification of additional regulators that compete and/or collaborate with DevR (DosR) to regulate its individual gene members.

* Corresponding author. Mailing address: Wadsworth Center, P.O. Box 22002, 120 New Scotland Avenue, Albany, NY 12201-2002. Phone: (518) 486-4253. Fax: (518) 402-4773. E-mail: kathleen.mcdonough{at}wadsworth.org

{triangledown} Published ahead of print on 7 April 2008.

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

Editor: V. J. DiRita

Infection and Immunity, June 2008, p. 2478-2489, Vol. 76, No. 6
0019-9567/08/$08.00+0     doi:10.1128/IAI.01443-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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