Department of Biology, Duke University, Durham, NC 27708, USA.
Center for Genomics and System Biology at NYU Department of Biology, New York University, NY, NY 10003, USA.
Nucleic Acids Res. 2024 Jan 11;52(1):125-140. doi: 10.1093/nar/gkad997.
Maintaining the intracellular iron concentration within the homeostatic range is vital to meet cellular metabolic needs and reduce oxidative stress. Previous research revealed that the haloarchaeon Halobacterium salinarum encodes four diphtheria toxin repressor (DtxR) family transcription factors (TFs) that together regulate the iron response through an interconnected transcriptional regulatory network (TRN). However, the conservation of the TRN and the metal specificity of DtxR TFs remained poorly understood. Here we identified and characterized the TRN of Haloferax volcanii for comparison. Genetic analysis demonstrated that Hfx. volcanii relies on three DtxR transcriptional regulators (Idr, SirR, and TroR), with TroR as the primary regulator of iron homeostasis. Bioinformatics and molecular approaches revealed that TroR binds a conserved cis-regulatory motif located ∼100 nt upstream of the start codon of iron-related target genes. Transcriptomics analysis demonstrated that, under conditions of iron sufficiency, TroR repressed iron uptake and induced iron storage mechanisms. TroR repressed the expression of one other DtxR TF, Idr. This reduced DtxR TRN complexity relative to that of Hbt. salinarum appeared correlated with natural variations in iron availability. Based on these data, we hypothesize that variable environmental conditions such as iron availability appear to select for increasing TRN complexity.
维持细胞内铁浓度在稳态范围内对于满足细胞代谢需求和减少氧化应激至关重要。先前的研究表明，盐杆菌属 Haloarchaeon 编码了四个白喉毒素阻遏物（DtxR）家族转录因子（TFs），它们通过相互关联的转录调控网络（TRN）共同调节铁反应。然而，TRN 的保守性和 DtxR TFs 的金属特异性仍知之甚少。在这里，我们鉴定并表征了 Haloferax volcanii 的 TRN 进行比较。遗传分析表明，Hfx. volcanii 依赖于三个 DtxR 转录调节因子（Idr、SirR 和 TroR），其中 TroR 是铁稳态的主要调节因子。生物信息学和分子方法揭示了 TroR 结合了一个保守的顺式调节元件，位于铁相关靶基因起始密码子上游约 100 个核苷酸处。转录组学分析表明，在铁充足的条件下，TroR 抑制铁摄取并诱导铁储存机制。TroR 抑制了另一个 DtxR TF 的表达，Idr。与 Hbt. salinarum 相比，这种减少的 DtxR TRN 复杂性似乎与铁可用性的自然变化有关。基于这些数据，我们假设可变的环境条件，如铁的可用性，似乎选择了增加 TRN 的复杂性。
