Erwin Kyle N, Nakano Shunji, Zuber Peter
Department of Environmental & Biomolecular Systems, OGI School of Science & Engineering, Oregon Health & Science University, 20000 NW Walker Rd., Beaverton, OR 97006, USA.
J Bacteriol. 2005 Jun;187(12):4042-9. doi: 10.1128/JB.187.12.4042-4049.2005.
Oxidative stress in Bacillus subtilis results in the accumulation of Spx protein, which exerts both positive and negative transcriptional control over a genome-wide scale through its interaction with the RNA polymerase alpha subunit. Previous microarray transcriptome studies uncovered a unique class of genes that are controlled by Spx-RNA polymerase interaction under normal growth conditions that do not promote Spx overproduction. These genes were repressed by Spx when sulfate was present as a sole sulfur source. The genes include those of the ytmI, yxeI, and ssu operons, which encode products resembling proteins that function in the uptake and desulfurization of organic sulfur compounds. Primer extension and analysis of operon-lacZ fusion expression revealed that the operons are repressed by sulfate and cysteine; however, Spx functioned only in sulfate-dependent repression. Both the ytmI operon and the divergently transcribed ytlI, encoding a LysR-type regulator that positively controls ytmI operon transcription, are repressed by Spx in sulfate-containing media. The CXXC motif of Spx, which is necessary for redox sensitive control of Spx activity in response to oxidative stress, is not required for sulfate-dependent repression. The yxeL-lacZ and ssu-lacZ fusions were also repressed in an Spx-dependent manner in media containing sulfate as the sole sulfur source. This work uncovers a new role for Spx in the control of sulfur metabolism in a gram-positive bacterium under nonstressful growth conditions.
枯草芽孢杆菌中的氧化应激会导致Spx蛋白积累，该蛋白通过与RNA聚合酶α亚基相互作用，在全基因组范围内发挥正负转录调控作用。先前的微阵列转录组研究发现了一类独特的基因，在正常生长条件下，这些基因受Spx - RNA聚合酶相互作用的控制，此时不会促进Spx过量产生。当硫酸盐作为唯一硫源存在时，这些基因被Spx抑制。这些基因包括ytmI、yxeI和ssu操纵子的基因，它们编码的产物类似于在有机硫化合物摄取和脱硫中起作用的蛋白质。引物延伸和操纵子 - lacZ融合表达分析表明，这些操纵子受硫酸盐和半胱氨酸抑制；然而，Spx仅在硫酸盐依赖性抑制中起作用。ytmI操纵子和与之反向转录的ytlI（编码正向控制ytmI操纵子转录的LysR型调节因子）在含硫酸盐的培养基中均被Spx抑制。Spx的CXXC基序是其在氧化应激时对氧化还原敏感控制活性所必需的，但在硫酸盐依赖性抑制中并非必需。在以硫酸盐作为唯一硫源的培养基中，yxeL - lacZ和ssu - lacZ融合也以Spx依赖性方式被抑制。这项工作揭示了Spx在非应激生长条件下对革兰氏阳性菌硫代谢控制中的新作用。
