Wolański Marcin, Krawiec Michał, Nieselt Kay, Schwarz Tobias, Dere Dilek, Krismer Bernhard, Cano-Prieto Carolina, Gross Harald, Zakrzewska-Czerwińska Jolanta
Faculty of Biotechnology, University of Wrocław, Wrocław, Poland.
Institute for Bioinformatics and Medical Informatics, University of Tübingen, Tübingen, Germany.
Appl Microbiol Biotechnol. 2025 Jun 24;109(1):150. doi: 10.1007/s00253-025-13485-3.
Brasilicardin A, BraA, is a secondary metabolite produced by the bacterium Nocardia terpenica, and a promising drug due to its potent immunosuppressive activity and low cytotoxicity. Currently, a semisynthetic approach confers the production of a complete compound but suffers from limited heterologous biosynthesis of BraA intermediates used in the chemical semi-synthesis steps leading to only lab-scale quantities of the compound. A better understanding of the gene expression regulatory pathways involved within the brasilicardin biosynthetic gene cluster, Bra-BGC, is a prerequisite to improving production titers further. However, the transcriptional regulation of the Bra-BGC has only been superficially analyzed, till now. In this study, we comprehensively analyze the functions of several unstudied transcriptional regulators, KstR, SdpR, and OmpR, encoded within the close vicinity of the Bra-BGC, and delve into the role of the previously described cluster-situated activator Bra12. We present that Bra12 and the novel regulator SdpR bind several DNA sequences located in the promoter regions of the genes essential for BraA biosynthesis. Subsequently, we demonstrate the complex regulatory network through which both regulators can control the activity of those gene promoters and thus gene expression in Bra-BGC. Furthermore, using the heterologous producer strain Amycolatopsis japonicum, we present that Bra12 and SdpR regulators play opposite roles in brasilicardin congener biosynthesis. Finally, we propose a comprehensive model of multilevel gene expression regulation in Bra-BGC and propose the roles of locally encoded transcriptional regulators. KEY POINTS: • Multiple regulators bind within the brasilicardin gene cluster. • Bra12 and SdpR are key regulators of brasilicardin biosynthesis. • The bra0 - 1 intergenic region is likely a key regulatory "hot-spot."
巴西利卡汀A(BraA)是由嗜热栖热放线菌产生的一种次生代谢产物,因其具有强大的免疫抑制活性和低细胞毒性而成为一种有前景的药物。目前,半合成方法可生产完整的化合物,但化学半合成步骤中使用的BraA中间体的异源生物合成有限,导致该化合物仅能在实验室规模生产。更好地理解巴西利卡汀生物合成基因簇(Bra-BGC)中涉及的基因表达调控途径是进一步提高产量滴度的先决条件。然而,到目前为止,对Bra-BGC的转录调控仅进行了表面分析。在本研究中,我们全面分析了位于Bra-BGC附近编码的几种未研究的转录调节因子KstR、SdpR和OmpR的功能,并深入研究了先前描述的簇状激活因子Bra12的作用。我们发现Bra12和新型调节因子SdpR结合了位于BraA生物合成必需基因启动子区域的几个DNA序列。随后,我们展示了这两种调节因子可以控制这些基因启动子活性从而调控Bra-BGC中基因表达的复杂调控网络。此外,使用异源生产菌株日本拟无枝酸菌,我们发现Bra12和SdpR调节因子在巴西利卡汀同系物生物合成中发挥相反的作用。最后,我们提出了Bra-BGC中多级基因表达调控的综合模型,并提出了局部编码转录调节因子的作用。要点:• 多个调节因子结合在巴西利卡汀基因簇内。• Bra12和SdpR是巴西利卡汀生物合成的关键调节因子。• bra0 - 1基因间区域可能是关键的调控“热点”。