Cholesterol utilization in mycobacteria is controlled by two TetR-type transcriptional regulators: kstR and kstR2

Abstract

Mycobacterium tuberculosis is able to use a variety of carbon sources in vivo and current knowledge suggests that cholesterol is used as a carbon source during infection. The catabolized cholesterol is used both as an energy source (ATP generation) and as a source of precursor molecules for the synthesis of complex methyl-branched fatty acids. In previous studies, we described a TetR-type transcriptional repressor, kstR, that controls the expression of a number of genes involved in cholesterol catabolism. In this study, we describe a second TetR-type repressor, which we call kstR2. We knocked this gene out in Mycobacterium smegmatis and used microarrays and quantitative RT-PCR to examine the effects on gene expression. We identified a palindromic regulatory motif for KstR2, showed that this motif is present in three promoter regions in mycobacteria and rhodococcus, and demonstrated binding of purified KstR2 to the motif. Using a combination of motif location analysis, gene expression analysis and the examination of gene conservation, we suggest that kstR2 controls the expression of a 15 gene regulon. Like kstR, kstR2 and the kstR2 regulon are highly conserved among the actinomycetes and studies in rhodococcus suggest a role for these genes in cholesterol catabolism. The functional significance of the regulon and implications for the control of cholesterol utilization are discussed.

Gene Cluster Encoding Cholate Catabolism in Rhodococcus spp

“…The other, ro04591 to ro04599, was upregulated only during growth on cholate but was likely expressed at a high constitutive level on cholesterol. Together, these two gene groups appear to correspond to the KstR2 regulon described in M. smegmatis (15). Thus, cluster 3 does not appear to encode the complete degradation of cholate, and a subset of genes in cluster 1 encoding degradation of rings C and D is upregulated during growth on cholate.…”

Shrinking the FadE Proteome of Mycobacterium tuberculosis: Insights into Cholesterol Metabolism through Identification of an α 2 β 2 Heterotetrameric Acyl Coenzyme A Dehydrogenase Family

“…In the M. tuberculosis genome, there are over 250 genes identified as involved in lipid, sterol, and fatty acid metabolism (29), and there are many variants of TetR-like transcriptional repressors throughout the M. tuberculosis genome. A large subset of the genes (ϳ80 to 90) in the M. tuberculosis cholesterol-regulated transcriptome are under the control of two TetR-like transcriptional repressors, KstR1 (also known as KstR) (30) and KstR2 (31).…”

The TetR Family of Regulators

“…Two TFRs, KstR and KstR2, control cholesterol degradation in M. tuberculosis (169)(170)(171)(172). The genes in the KstR and KstR2 regulons are known to be upregulated in vivo and are important for virulence of M. tuberculosis (173).…”