Discovery of a Cryptic Antifungal Compound from Streptomyces albus J1074 Using High-Throughput Elicitor Screens. Author Fei Xu, Behnam Nazari, Kyuho Moon, Leah Bushin, Mohammad Seyedsayamdost Publication Year 2017 Type Journal Article Abstract An important unresolved issue in microbial secondary metabolite production is the abundance of biosynthetic gene clusters that are not expressed under typical laboratory growth conditions. These so-called silent or cryptic gene clusters are sources of new natural products, but how they are silenced, and how they may be rationally activated are areas of ongoing investigation. We recently devised a chemogenetic high-throughput screening approach ("HiTES") to discover small molecule elicitors of silent biosynthetic gene clusters. This method was successfully applied to a Gram-negative bacterium; it has yet to be implemented in the prolific antibiotic-producing streptomycetes. Herein we have developed a high-throughput transcriptional assay format in Streptomyces spp. by leveraging eGFP, inserted both at a neutral site and inside the biosynthetic cluster of interest, as a read-out for secondary metabolite synthesis. Using this approach, we successfully used HiTES to activate a silent gene cluster in Streptomyces albus J1074. Our results revealed the cytotoxins etoposide and ivermectin as potent inducers, allowing us to isolate and structurally characterize 14 novel small molecule products of the chosen cluster. One of these molecules is a novel antifungal, while several others inhibit a cysteine protease implicated in cancer. Studies addressing the mechanism of induction by the two elicitors led to the identification of a pathway-specific transcriptional repressor that silences the gene cluster under standard growth conditions. The successful application of HiTES will allow future interrogations of the biological regulation and chemical output of the countless silent gene clusters in Streptomyces spp. Keywords High-Throughput Screening Assays, Drug Discovery, Biological Products, Molecular Conformation, Streptomyces, Antifungal Agents Journal J Am Chem Soc Volume 139 Issue 27 Pages 9203-9212 Date Published 2017 Jul 12 ISSN Number 1520-5126 DOI 10.1021/jacs.7b02716 Alternate Journal J Am Chem Soc PMCID PMC5617735 PMID 28590725 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML