Affiliation:
1. 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
Abstract
ABSTRACT
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.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
32 articles.
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