Division of Environmental and Biomolecular Systems, Institute of Environmental Health, Oregon Health and Science University, Beaverton, OR, USA.
J Bacteriol. 2012 Apr;194(7):1679-88. doi: 10.1128/JB.06486-11. Epub 2012 Jan 27.
The NO-sensitive NsrR repressor of Bacillus subtilis, which carries a [4Fe-4S] cluster, controls transcription of nasD and hmp (class I regulation) under anaerobic conditions. Here, we describe another class of NsrR regulation (class II regulation) that controls a more diverse collection of genes. Base substitution analysis showed that [4Fe-4S]-NsrR recognizes a partial dyad symmetry within the class I cis-acting sites, whereas NO-insensitive interaction of NsrR with an A+T-rich class II regulatory site showed relaxed sequence specificity. Genome-wide transcriptome studies identified genes that are under the control of the class II NsrR regulation. The class II NsrR regulon includes genes controlled by both AbrB and Rok repressors, which also recognize A+T-rich sequences, and by the Fur repressor. Transcription of class II genes was elevated in an nsrR mutant during anaerobic fermentative growth with pyruvate. Although NsrR binding to the class II regulatory sites was NO insensitive in vitro, transcription of class II genes was moderately induced by NO, which involved reversal of NsrR-dependent repression, suggesting that class II repression is also NO sensitive. In all NsrR-repressed genes tested, the loss of NsrR repressor activity was not sufficient to induce transcription as induction required the ResD response regulator. The ResD-ResE signal transduction system is essential for activation of genes involved in aerobic and anaerobic respiration. This study indicated coordinated regulation between ResD and NsrR and uncovered a new role of ResD and NsrR in transcriptional regulation during anaerobiosis of B. subtilis.
枯草芽孢杆菌的 NsrR 阻遏蛋白对 NO 敏感，它携带一个 [4Fe-4S] 簇，在厌氧条件下控制 nasD 和 hmp 的转录（I 类调控）。在这里，我们描述了 NsrR 调控的另一种类型（II 类调控），它控制着更多种类的基因。碱基取代分析表明，[4Fe-4S]-NsrR 识别 I 类顺式作用位点中的部分二分对称结构，而 NsrR 与富含 A+T 的 II 类调节位点的非 NO 敏感相互作用显示出宽松的序列特异性。全基因组转录组研究确定了受 II 类 NsrR 调控的基因。II 类 NsrR 调控子包括受 AbrB 和 Rok 阻遏物控制的基因，它们也识别富含 A+T 的序列，以及 Fur 阻遏物。在厌氧发酵生长过程中，丙酮酸作为碳源时，II 类基因的转录在 nsrR 突变体中升高。尽管 NsrR 与 II 类调节位点的结合在体外对 NO 不敏感，但 II 类基因的转录被 NO 适度诱导，这涉及到 NsrR 依赖性抑制的逆转，表明 II 类抑制也是对 NO 敏感的。在所测试的所有受 NsrR 抑制的基因中，NsrR 抑制活性的丧失不足以诱导转录，因为诱导需要 ResD 响应调节子。ResD-ResE 信号转导系统对于激活参与需氧和厌氧呼吸的基因是必不可少的。本研究表明 ResD 和 NsrR 之间存在协调调控，并揭示了 ResD 和 NsrR 在枯草芽孢杆菌厌氧条件下转录调控中的新作用。
