The mycobacterium tuberculosis extracytoplasmic-function sigma factor SigL regulates polyketide synthases and secreted or membrane proteins and is required for virulence
The mycobacterium tuberculosis extracytoplasmic-function sigma factor SigL regulates polyketide synthases and secreted or membrane proteins and is required for virulence
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DOI：
10.1128/jb.187.20.7062-7071.2005
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发表时间：
2005-10-01
影响因子：
3.2
通讯作者：
Husson, RN
中科院分区：
文献类型：
--
作者：
Hahn, MY;Raman, S;Husson, RN
结核分枝杆菌sigL编码胞质外功能（ECF）σ因子，并且与包含保守的HXXXCXXC序列的膜蛋白基因（Rv 0736）相邻。该基序存在于调节几种ECF σ因子的抗σ因子中，包括控制氧化应激反应的那些。在这项工作中，发现SigL和Rv 0736共转录，并且Rv 0736的胞内结构域显示与SigL特异性相互作用，表明Rv 0736可能编码SigL的抗σ因子。个核磁结核病sigL突变体对几种氧化和亚硝化应激的敏感性并不比亲本菌株高，并且sigL表达在对这些应激的响应中没有增加。在体内，sigL从弱SigL非依赖性启动子表达，也从第二SigL依赖性启动子表达。为了鉴定SigL调节的基因，sigL过表达，并进行全局转录的微阵列分析。四个小操纵子sigL（Rv 0735）-Rv 0736、mpt 53（Rv 2878 c）-Rv 2877 c、pks 10（Rv 1660）-pks 7（Rv 1661）和Rv 1139 c-Rv 1138 c是sigL过表达菌株中最高度上调的基因。对这些操纵子的SigL依赖性转录起始位点进行了定位，并鉴定了-35区的共有启动子序列TGAACC和-10区的CGTgtc。在体外，纯化的SigL特异性地从sigL、mpt 53和pks 10的启动子启动转录。其他基因，包括四个PE（-）PGRS基因，似乎间接由SigL调节。在体内鼠感染模型中，sigL突变株显示出显著的减毒，表明sigL调节子在M.结核病发病机制
Mycobacterium tuberculosis sigL encodes an extracytoplasmic function (ECF) sigma factor and is adjacent to a gene for a membrane protein (Rv0736) that contains a conserved HXXXCXXC sequence. This motif is found in anti-sigma factors that regulate several ECF sigma factors, including those that control oxidative stress responses. In this work, SigL and Rv0736 were found to be cotranscribed, and the intracellular domain of Rv0736 was shown to interact specifically with SigL, suggesting that Rv0736 may encode an anti-sigma factor of SigL. An M. tuberculosis sigL mutant was not more susceptible than the parental strain to several oxidative and nitrosative stresses, and sigL expression was not increased in response to these stresses. In vivo, sigL is expressed from a weak SigL-independent promoter and also from a second SigL-dependent promoter. To identify SigL-regulated genes, sigL was overexpressed and microarray analysis of global transcription was performed. Four small operons, sigL (Rv0735)-Rv0736, mpt53 (Rv2878c)-Rv2877c, pks10 (Rv1660)-pks7 (Rv1661), and Rv1139c-Rv1138c, were among the most highly upregulated genes in the sigL-overexpressing strain. SigL-dependent transcription start sites of these operons were mapped, and the consensus promoter sequences TGAACC in the -35 region and CGTgtc in the -10 region were identified. In vitro, purified SigL specifically initiated transcription from the promoters of sigL, mpt53, and pks10. Additional genes, including four PE(-)PGRS genes, appear to be regulated indirectly by SigL. In an in vivo murine infection model, the sigL mutant strain showed marked attenuation, indicating that the sigL regulon is important in M. tuberculosis pathogenesis.