Rios-Delgado Gustavo, McReynolds Aubrey K G, Pagella Emma A, Norambuena Javiera, Briaud Paul, Zheng Vincent, Munneke Matthew J, Kim Jisun, Racine Hugo, Carroll Ronan K, Zelzion Ehud, Skaar Eric, Bose Jeffrey L, Parker Dane, Lalaouna David, Boyd Jeffrey M
Department of Biochemistry and Microbiology, Rutgers, the State University of New Jersey, 76 Lipman Dr, New Brunswick, NJ 08901, USA.
Department of Microbiology, Molecular Genetics, and Immunology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA.
Nucleic Acids Res. 2025 Feb 8;53(4). doi: 10.1093/nar/gkae1243.
Staphylococcus aureus has evolved mechanisms to cope with low iron (Fe) availability in host tissues. Staphylococcus aureus uses the ferric uptake transcriptional regulator (Fur) to sense titers of cytosolic Fe. Upon Fe depletion, apo-Fur relieves transcriptional repression of genes utilized for Fe uptake. We demonstrate that an S. aureus Δfur mutant has decreased expression of acnA, which codes for the Fe-dependent enzyme aconitase. This prevents the Δfur mutant from growing with amino acids as sole carbon and energy sources. We used a suppressor screen to exploit this phenotype and determined that a mutation that decreases the transcription of isrR, which produces a regulatory RNA, increased acnA expression, thereby enabling growth. Directed mutation of bases predicted to facilitate the interaction between the acnA transcript and IsrR, decreased the ability of IsrR to control acnA expression in vivo and IsrR bound to the acnA transcript in vitro. IsrR also bound transcripts coding the alternate tricarboxylic acid cycle proteins sdhC, mqo, citZ and citM. Whole-cell metal analyses suggest that IsrR promotes Fe uptake and increases intracellular Fe not ligated by macromolecules. Lastly, we determined that Fur and IsrR promote infection using murine skin and acute pneumonia models.
金黄色葡萄球菌已进化出应对宿主组织中铁（Fe）可用性低的机制。金黄色葡萄球菌利用铁摄取转录调节因子（Fur）来感知胞质铁的滴度。在铁耗尽时，脱辅基Fur解除对铁摄取相关基因转录抑制。我们证明，金黄色葡萄球菌Δfur突变体中编码铁依赖性酶乌头酸酶的acnA表达降低。这阻止了Δfur突变体以氨基酸作为唯一碳源和能源生长。我们利用抑制子筛选来利用这种表型，并确定一个降低产生调控RNA的isrR转录的突变增加了acnA表达，从而实现生长。预测促进acnA转录本与IsrR相互作用的碱基的定向突变，降低了IsrR在体内控制acnA表达的能力，并且IsrR在体外与acnA转录本结合。IsrR还与编码替代三羧酸循环蛋白sdhC、mqo、citZ和citM的转录本结合。全细胞金属分析表明，IsrR促进铁摄取并增加未与大分子结合的细胞内铁。最后，我们利用小鼠皮肤和急性肺炎模型确定Fur和IsrR促进感染。
