Department of Molecular Biology, School of Biological Sciences, Centre for Advanced Studies in Functional and Organismal Genomics, Madurai Kamaraj University [University with Potential for Excellence], Madurai 625 021, India.
Department of Molecular Biology, School of Biological Sciences, Centre for Advanced Studies in Functional and Organismal Genomics, Madurai Kamaraj University [University with Potential for Excellence], Madurai 625 021, India.
Gene. 2019 Sep 10;713:143951. doi: 10.1016/j.gene.2019.143951. Epub 2019 Jun 30.
Rifampicin (RIF) is still a first line of antibiotic in the treatment of bacterial diseases, in particular the Mycobacterial infections. The antimicrobial activity of RIF is attributed to its ability to inhibit transcription by binding to the β subunit of bacterial RNA polymerase (encoded by rpoB). Continued use of this drug resulted in the emergence of RIF resistant rpoB mutations in a high frequency that compels the use of RIF almost exclusively in drug combinations. As of date, a broad array of rif mutations have been isolated and characterized by different research groups. Studies on rpoB mutations strengthen the view that the β subunit of RNA polymerase (RNAP) is very crucial in modulating transcription thereby leading to differential gene expression. Very recently we have reported the transcriptome profile of rpoB12 mutant that provides molecular evidence that presence of rpoB12 mutation modulates the transcription of about 450 genes. Here we present a maiden report that rpoB mutations that substitute Tyr at the Rif binding pocket (RBP) of β subunit of RNA polymerase are able to suppress the over-production of colanic acid capsular polysaccharide (Ces phenotype) in Δlon mutant of Escherichia coli. Further analyses of the rif mutants involving their growth pattern on LB at higher temperature (42 °C), LB media without NaCl, survival in LB media with acidic pH (pH - 3) and motility revealed that only rpoB12 (His526Tyr) and rpoB137 (Ser522Tyr) affected all the above mentioned physiological parameters in addition to the elicitation of Ces phenotype. These two rif mutations confer fast movement to RNAP and they bear Tyr as the substituted amino acid in the RBP. This is perhaps the first study that brings out the possible role of Tyr in the RBP and its participation in the global gene expression. This study also envisages the point that amino acid residues that share the properties of Tyr in the RBP can be employed as a tool to bring out differential gene expression which would certainly have basic and applied values for the mankind.
利福平（RIF）仍然是治疗细菌疾病，特别是分枝杆菌感染的一线抗生素。RIF 的抗菌活性归因于其通过与细菌 RNA 聚合酶的β亚基（由 rpoB 编码）结合来抑制转录的能力。该药物的持续使用导致了高频率的 RIF 耐药 rpoB 突变的出现，这迫使 RIF 几乎完全用于药物联合治疗。迄今为止，不同的研究小组已经分离并表征了广泛的 rif 突变。对 rpoB 突变的研究加强了这样一种观点，即 RNA 聚合酶（RNAP）的β亚基在调节转录方面非常重要，从而导致基因表达的差异。就在最近，我们报告了 rpoB12 突变体的转录组图谱，该图谱提供了分子证据，表明 rpoB12 突变会调节大约 450 个基因的转录。在这里，我们首次报告了 rpoB 突变，该突变取代了 RNA 聚合酶β亚基 Rif 结合口袋（RBP）中的 Tyr，能够抑制大肠杆菌Δlon 突变体中 colanic 酸荚膜多糖（Ces 表型）的过度产生。对 Rif 突变体的进一步分析，包括它们在较高温度（42°C）下在 LB 上的生长模式、不含 NaCl 的 LB 培养基、在酸性 pH（pH-3）的 LB 培养基中的存活能力和运动性，表明只有 rpoB12（His526Tyr）和 rpoB137（Ser522Tyr）除了引发 Ces 表型外，还影响了所有上述生理参数。这两种 Rif 突变赋予了 RNAP 快速运动的能力，并且它们在 RBP 中带有 Tyr 作为取代氨基酸。这也许是第一个阐明 RBP 中 Tyr 可能作用及其参与全局基因表达的研究。这项研究还设想了这样一个观点，即 RBP 中具有 Tyr 性质的氨基酸残基可以作为一种工具来实现差异基因表达，这无疑将对人类具有基础和应用价值。
