Discovery of a Cryptic Antifungal Compound from Streptomyces albus J1074 Using High-Throughput Elicitor Screens.

TitleDiscovery of a Cryptic Antifungal Compound from Streptomyces albus J1074 Using High-Throughput Elicitor Screens.
Publication TypeJournal Article
Year of Publication2017
AuthorsXu, F, Nazari, B, Moon, K, Bushin, LB, Seyedsayamdost, MR
JournalJ Am Chem Soc
Volume139
Issue27
Pagination9203-9212
Date Published2017 Jul 12
ISSN1520-5126
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.

DOI10.1021/jacs.7b02716
Alternate JournalJ. Am. Chem. Soc.
PubMed ID28590725
PubMed Central IDPMC5617735
Grant ListDP2 AI124786 / AI / NIAID NIH HHS / United States