Negative Transcriptional Regulation of the ilv-leu Operon for Biosynthesis of Branched-Chain Amino Acids through the Bacillus subtilis Global Regulator TnrA
Negative Transcriptional Regulation of the ilv-leu Operon for Biosynthesis of Branched-Chain Amino Acids through the Bacillus subtilis Global Regulator TnrA
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DOI：
10.1128/jb.186.23.7971-7979.2004
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发表时间：
2004-12
影响因子：
3.2
通讯作者：
Shigeo Tojo;T. Satomura;K. Morisaki;Ken-ichi Yoshida;K. Hirooka;Y. Fujita
中科院分区：
文献类型：
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作者：
Shigeo Tojo;T. Satomura;K. Morisaki;Ken-ichi Yoshida;K. Hirooka;Y. Fujita
摘要 枯草芽孢杆菌 ilv-leu 操纵子参与支链氨基酸（缬氨酸、异亮氨酸和亮氨酸）的合成。在氮限制条件下的对数期生长过程中，ilv-leu操纵子的表达受到两到三倍的抑制，这最初是通过DNA微阵列分析来比较野生型和tnrA突变菌株的转录组而检测到的，后来通过lacZ融合和Northern实验得到了证实。全基因组 TnrA 框搜索揭示了 ilv-leu 操纵子转录起始碱基上游约 200 bp 处的候选框，通过凝胶阻滞和 DNase I 足迹分析验证了与其结合的 TnrA。 TnrA 盒序列的缺失和碱基取代影响了 ilv-leu 启动子的体内活性，这意味着与该盒结合的 TnrA 可能能够通过 DNA 弯曲来抑制启动子活性。 TnrA 对 ilv-leu 操纵子表达的负控制被认为代表了相当精细的调节（两到三倍），是氮和氨基酸代谢之间的一种新的调节联系。
ABSTRACT The Bacillus subtilis ilv-leu operon is involved in the synthesis of branched-chain amino acids (valine, isoleucine, and leucine). The two- to threefold repression of expression of the ilv-leu operon during logarithmic-phase growth under nitrogen-limited conditions, which was originally detected by a DNA microarray analysis to compare the transcriptomes from the wild-type and tnrA mutant strains, was confirmed by lacZ fusion and Northern experiments. A genome-wide TnrA box search revealed a candidate box approximately 200 bp upstream of the transcription initiation base of the ilv-leu operon, the TnrA binding to which was verified by gel retardation and DNase I footprinting analyses. Deletion and base substitution of the TnrA box sequence affected the ilv-leu promoter activity in vivo, implying that TnrA bound to the box might be able to inhibit the promoter activity, possibly through DNA bending. The negative control of the expression of the ilv-leu operon by TnrA, which is considered to represent rather fine-tuning (two- to threefold), is a novel regulatory link between nitrogen and amino acid metabolism.