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Triggering the expression of a silent gene cluster from genetically intractable bacteria results in scleric acid discovery

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Abstract

In this study, we report the rapid characterisation of a novel microbial natural product resulting from the rational derepression of a silent gene cluster. A conserved set of five regulatory genes was used as a query to search genomic databases and identify atypical biosynthetic gene clusters (BGCs). A 20-kb BGC from the genetically intractable Streptomyces sclerotialus bacterial strain was captured using yeast-based homologous recombination and introduced into validated heterologous hosts. CRISPR/Cas9-mediated genome editing was then employed to rationally inactivate the key transcriptional repressor and trigger production of an unprecedented class of hybrid natural products exemplified by (2-(benzoyloxy)acetyl)-L-proline, named scleric acid. Subsequent rounds of CRISPR/Cas9-mediated gene deletions afforded a selection of biosynthetic gene mutant strains which led to a plausible biosynthetic pathway for scleric acid assembly. Synthetic standards of scleric acid and a key biosynthetic intermediate were also prepared to confirm the chemical structures we proposed. The assembly of scleric acid involves two unique condensation reactions catalysed by a single NRPS module and an ATP-grasp enzyme that link a proline and a benzoyl residue to each end of a rare hydroxyethyl-ACP intermediate, respectively. Scleric acid was shown to exhibit moderate inhibition activity against Mycobacterium tuberculosis, as well as inhibition of the cancer-associated metabolic enzyme nicotinamide N-methyltransferase (NNMT).

Graphical abstract: Triggering the expression of a silent gene cluster from genetically intractable bacteria results in scleric acid discovery

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Publication details

The article was received on 26 Aug 2018, accepted on 11 Oct 2018 and first published on 19 Oct 2018


Article type: Edge Article
DOI: 10.1039/C8SC03814G
Citation: Chem. Sci., 2019, Advance Article
  • Open access: Creative Commons BY license
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    Triggering the expression of a silent gene cluster from genetically intractable bacteria results in scleric acid discovery

    F. Alberti, D. J. Leng, I. Wilkening, L. Song, M. Tosin and C. Corre, Chem. Sci., 2019, Advance Article , DOI: 10.1039/C8SC03814G

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