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Journal of Bacteriology, September 2007, p. 6213-6221, Vol. 189, No. 17
0021-9193/07/$08.00+0     doi:10.1128/JB.00492-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Regulation of the {alpha}-Crystallin Gene acr2 by the MprAB Two-Component System of Mycobacterium tuberculosis{triangledown} ,{dagger}

Xiuhua Pang and Susan T. Howard*

Department of Microbiology and Immunology, Center for Pulmonary and Infectious Disease Control, University of Texas Health Center at Tyler, 11937 US Highway 271, Tyler, Texas 75708

Received 30 March 2007/ Accepted 20 June 2007

Coordinated regulation of molecular chaperones is an important feature of the bacterial stress response. The small molecular chaperone gene acr2 of Mycobacterium tuberculosis is activated by exposure to several stresses, including heat and the detergent sodium dodecyl sulfate (SDS). In this study, we show that acr2 is directly regulated by the MprAB two-component system, and that MprAB has both positive and negative effects on acr2 expression. mRNA analyses showed that acr2 expression levels were lower under SDS stress and control conditions but higher under heat shock in an mprAB deletion mutant than they were in the parental strain. Parental expression patterns were restored in an mprAB-complemented strain. Western blotting using an anti-Acr2 antibody showed that Acr2 protein synthesis correlated with mRNA levels. Primer extension identified one transcriptional start point (TSP) for acr2 in all three strains under control and stress conditions. Electrophoresis mobility shift assays revealed multiple MprA binding sites in the acr2 promoter, including one downstream and three upstream of the acr2 TSP, with one overlapping the binding sites predicted for SigE, SigH, and HspR. DNA footprinting confirmed that MprA protected large sections of the acr2 promoter region. Expression of several housekeeping genes under SDS stress also was evaluated, revealing the upregulation of large molecular chaperone genes and, unexpectedly, sigA, with slightly lower sigA mRNA levels detected in the mprAB deletion mutant than in the wild type. In contrast to Acr2, SigA protein synthesis did not correlate with mRNA expression. Overall, the data indicated that MprA has complex interactions with the acr2 promoter and indirect effects on major housekeeping genes.

* Corresponding author. Mailing address: CPIDC, BMR D617, University of Texas Health Center at Tyler, 11937 US Highway 271, Tyler, TX 75708-3154. Phone: (903) 877-7684. Fax: (903) 877-7989. E-mail: susan.howard{at}uthct.edu

{triangledown} Published ahead of print on 29 June 2007.

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

Journal of Bacteriology, September 2007, p. 6213-6221, Vol. 189, No. 17
0021-9193/07/$08.00+0     doi:10.1128/JB.00492-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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