Department of Pathology and Infectious Diseases, The Royal Veterinary College, Centre for Emerging, Endemic and Exotic Disease, Hawkshead Lane, Hertfordshire, AL9 7TA, UK.
Laboratory of Structural Biology and Maurice Wilkins Centre for Molecular Biodiscovery, School of Biological Sciences, University of Auckland, New Zealand.
Microbiology (Reading). 2010 May;156(Pt 5):1362-1371. doi: 10.1099/mic.0.034538-0. Epub 2010 Feb 18.
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.
结核分枝杆菌能够在体内利用多种碳源，目前的知识表明胆固醇在感染过程中被用作碳源。代谢的胆固醇既可用作能量来源（ATP 生成），也可用作合成复杂支链甲基脂肪酸的前体分子的来源。在以前的研究中，我们描述了一种 TetR 型转录抑制剂 kstR，它控制着参与胆固醇代谢的许多基因的表达。在这项研究中，我们描述了第二种 TetR 型抑制剂 kstR2。我们敲除了分枝杆菌中的该基因，并使用微阵列和定量 RT-PCR 来检查对基因表达的影响。我们确定了 KstR2 的一个回文调节基序，表明该基序存在于分枝杆菌和红球菌的三个启动子区域中，并证明了纯化的 KstR2 与该基序结合。通过基序位置分析、基因表达分析和基因保守性检查的组合，我们推测 kstR2 控制着一个包含 15 个基因的调控子的表达。与 kstR 一样，kstR2 和 kstR2 调控子在放线菌中高度保守，在红球菌中的研究表明这些基因在胆固醇代谢中起作用。讨论了该调控子的功能意义及其对胆固醇利用的控制的影响。
