The global regulator Spx functions in the control of organosulfur metabolism in Bacillus subtilis
The global regulator Spx functions in the control of organosulfur metabolism in Bacillus subtilis
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DOI：
10.1128/jb.00443-06
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发表时间：
2006-08-01
影响因子：
3.2
通讯作者：
Zuber, Peter
中科院分区：
文献类型：
--
作者：
Choi, Soon-Yong;Reyes, Dindo;Zuber, Peter
SPX是枯草芽孢杆菌氧化应激反应的全球转录调节因子。它的靶标是RNA聚合酶，在那里它接触阿尔法亚单位C末端结构域。最近，有证据表明Spx参与了硫酸盐依赖的有机硫利用操纵子的调控，包括ytmI、yxeI、SSU和yrrT操纵子。YrrT操纵子包括由S-腺苷蛋氨酸通过中间体S-腺苷同型半胱氨酸、核糖基同型半胱氨酸、同型半胱氨酸和胱硫氨酸合成半胱氨酸的基因。这些操纵子还受到半胱氨酸生物合成操纵子的抑制子Cymr的负调控。所有操纵子在含有半胱氨酸或硫酸盐的介质中被抑制，但在含有替代硫源蛋氨酸的介质中被解压。SPX被发现在硫酸盐介质中负向控制这些操纵子的表达，部分是通过刺激Cymr基因的表达。此外，基因芯片分析、YrrT-LacZ融合表达的监测和体外转录研究表明，Spx在以蛋氨酸为唯一硫源的培养基中直接激活yrrT操纵子的表达。这些实验揭示了Spx在不受干扰的稳定生长过程中控制基因表达的其他作用。
Spx is a global transcriptional regulator of the oxidative stress response in Bacillus subtilis. Its target is RNA polymerase, where it contacts the alpha subunit C-terminal domain. Recently, evidence was presented that Spx participates in sulfate-dependent control of organosulfur utilization operons, including the ytmI, yxeI, ssu, and yrrT operons. The yrrT operon includes the genes that function in cysteine synthesis from S-adenosylmethionine through intermediates S-adenosylhomocysteine, ribosylhomocysteine, homocysteine, and cystathionine. These operons are also negatively controlled by CymR, the repressor of cysteine biosynthesis operons. All of the operons are repressed in media containing cysteine or sulfate but are derepressed in medium containing the alternative sulfur source, methionine. Spx was found to negatively control the expression of these operons in sulfate medium, in part, by stimulating the expression of the cymR gene. In addition, microarray analysis, monitoring of yrrT-lacZ fusion expression, and in vitro transcription studies indicate that Spx directly activates yrrT operon expression during growth in medium containing methionine as sole sulfur source. These experiments have uncovered additional roles for Spx in the control of gene expression during unperturbed, steady-state growth.