Gamma Butyrolactones as Biosynthetic Gene Cluster Inducers

Project Summary/Abstract Historically, natural products (NPs) from Streptomyces have been rich sources for medicines including antibiotics, antifungals, anticancer agents and many others; however, traditional NP isolation techniques (i.e. screening culture isolates for antibiotic activity) are no longer effective as evidenced by the high rates of rediscovery.

A significant proportion of the Streptomyces genome (up to 10%) is devoted to genes encoding the biosynthesis of natural products; however, whole genome sequencing of diverse Streptomyces has revealed the presence of many transcriptionally inactive (or cryptic) biosynthesis gene clusters (BCGs).

These cryptic BCGs have yet to be characterized which provides strong evidence for the existence of many bioactive NPs that have not yet been discovered. A significant gap remains in the strategies available to discover new bioactive NPs from cryptic BGCs.

To maximize the success of NP potential from Streptomyces we propose to study a class of BGC inducers (?- butyrolactones) to probe the biochemical connection between BGC elicitation and NP production.

To this end, we propose three interrelated aims focusing on (1) the organic synthesis of a library of ?-butyrolactones, (2) development of a novel BGC elicitation assay and (3) isolation and characterization of novel NPs from diverse Streptomyces. Herein, we have devised synthetic routes for rapid generation of diverse ?-butyrolactones.

In parallel, we will develop a green fluorescent protein (GFP) bioassay for both known and novel ?-butyrolactone receptors predicted via a generated sequence similarity network (SSN).

With this in hand, transcription of cryptic BGCs in diverse Streptomyces cultures will be induced by treatment with synthetic ?-butyrolactones. This proposal will identify novel inducers of BGCs and concurrently result in the identification of novel NPs.

The natural products identified will be tested for antimicrobial and anticancer activity and mechanism of action studies will be performed in future studies.

Overall, this work will result in the identification of bioactive NPs and will provide a means for the discovery of many more.