Department of Microbiology and Cell Biology, Centre for Infectious Disease Research, Indian Institute of Science, Bangalore 560012, India.
Department of Structural Biology, CSIR-Institute of Genomics and Integrative Biology, South Campus, Mathura Road, New Delhi 110020, India; Academy of Scientific and Innovative Research (AcSIR), Anusandhan Bhawan, 2 Rafi Marg, New Delhi 110001, India.
Redox Biol. 2018 Oct;19:116-133. doi: 10.1016/j.redox.2018.08.006. Epub 2018 Aug 13.
Oxidative stress response in bacteria is mediated through coordination between the regulators of oxidant-remediation systems (e.g. OxyR, SoxR) and nucleoid condensation (e.g. Dps, Fis). However, these genetic factors are either absent or rendered non-functional in the human pathogen Mycobacterium tuberculosis (Mtb). Therefore, how Mtb organizes genome architecture and regulates gene expression to counterbalance oxidative imbalance is unknown. Here, we report that an intracellular redox-sensor, WhiB4, dynamically links genome condensation and oxidative stress response in Mtb. Disruption of WhiB4 affects the expression of genes involved in maintaining redox homeostasis, central metabolism, and respiration under oxidative stress. Notably, disulfide-linked oligomerization of WhiB4 in response to oxidative stress activates the protein's ability to condense DNA. Further, overexpression of WhiB4 led to hypercondensation of nucleoids, redox imbalance and increased susceptibility to oxidative stress, whereas WhiB4 disruption reversed this effect. In accordance with the findings in vitro, ChIP-Seq data demonstrated non-specific binding of WhiB4 to GC-rich regions of the Mtb genome. Lastly, data indicate that WhiB4 deletion affected the expression of ~ 30% of genes preferentially bound by the protein, suggesting both direct and indirect effects on gene expression. We propose that WhiB4 structurally couples Mtb's response to oxidative stress with genome organization and transcription.
细菌中的氧化应激反应是通过氧化剂修复系统（如 OxyR、SoxR）和核凝聚（如 Dps、Fis）的调节剂之间的协调来介导的。然而，这些遗传因素在人类病原体结核分枝杆菌（Mtb）中要么缺失，要么失去功能。因此，Mtb 如何组织基因组结构并调节基因表达以平衡氧化失衡尚不清楚。在这里，我们报告一种细胞内氧化还原传感器 WhiB4，它在 Mtb 中动态连接基因组凝聚和氧化应激反应。破坏 WhiB4 会影响涉及维持氧化还原稳态、中心代谢和呼吸作用的基因在氧化应激下的表达。值得注意的是，氧化应激下 WhiB4 的二硫键连接寡聚化激活了其凝聚 DNA 的能力。此外，WhiB4 的过表达导致核凝聚、氧化还原失衡和对氧化应激的敏感性增加，而 WhiB4 的破坏则逆转了这种效应。与体外发现一致，ChIP-Seq 数据表明 WhiB4 与 Mtb 基因组中富含 GC 的区域非特异性结合。最后，数据表明 WhiB4 缺失会影响约 30%的优先与该蛋白结合的基因的表达，这表明对基因表达具有直接和间接的影响。我们提出 WhiB4 结构上使 Mtb 对氧化应激的反应与基因组组织和转录偶联。
