National Key Laboratory of Agricultural Microbiology, Center for Proteomics Research, College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
BMC Microbiol. 2010 Sep 16;10:242. doi: 10.1186/1471-2180-10-242.
The two-component systems of Mycobacterium tuberculosis are apparently required for its growth and resistance in hostile host environments. In such environments, MtrAB has been reported to regulate the expression of the M. tuberculosis replication initiator gene, dnaA. However, the dnaA promoter binding sites and many potential target genes for MtrA have yet to be precisely characterized.
In this study, a 7 bp sequence motif in the dnaA promoter region was identified for MtrA binding using DNaseI footprinting assays and surface plasmon resonance (SPR) analysis. Approximately 420 target genes potentially regulated by MtrA, including the isoniazid inducible gene iniB, were further characterized from M. tuberculosis and M. smegmatis genomes. When assayed using quantitative real-time PCR (qRT-PCR), many of the target genes demonstrated significant expression changes when the antisense mRNA of the mtrA gene was expressed in M. smegmatis. The recombinant mycobacteria grew in length and were more sensitive to two anti-tuberculosis drugs, isoniazid and streptomycin.
These findings yield critical information about the regulatory mechanisms of the MtrAB two-component system and its role in the drug resistance of M. smegmatis.
结核分枝杆菌的双组分系统显然是其在恶劣的宿主环境中生长和抵抗的必需条件。在这种环境中，已经报道 MtrAB 调节结核分枝杆菌复制起始基因 dnaA 的表达。然而，dnaA 启动子结合位点和 MtrA 的许多潜在靶基因尚未得到精确表征。
在这项研究中，使用 DNaseI 足迹分析和表面等离子体共振（SPR）分析鉴定了 dnaA 启动子区域中的 7 个 bp 序列基序，用于 MtrA 结合。从结核分枝杆菌和耻垢分枝杆菌基因组中进一步鉴定了大约 420 个潜在受 MtrA 调控的靶基因，包括异烟肼诱导基因 iniB。使用定量实时 PCR（qRT-PCR）进行检测时，当在耻垢分枝杆菌中表达 mtrA 基因的反义 mRNA 时，许多靶基因的表达发生了显著变化。重组分枝杆菌的长度增加，对两种抗结核药物异烟肼和链霉素更加敏感。
这些发现提供了有关 MtrAB 双组分系统调控机制及其在耻垢分枝杆菌耐药性中的作用的关键信息。
