Identification and Characterization of the Chaetoviridin and Chaetomugilin Gene Cluster in Chaetomium globosum Reveal Dual Functions of an Iterative Highly-Reducing Polyketide Synthase

Abstract

We report the identification and characterization of the caz biosynthetic cluster from C. globosum and the characterization of a highly-reducing polyketide synthase (PKS) that acts in both a sequential and convergent manner with a nonreducing PKS to form the chaetomugilin and chaetoviridin azaphilones. Genetic inactivation studies verified the involvement of individual caz genes in the biosynthesis of the azaphilones. Through in vitro reconstitution, we demonstrated the in vitro synthesis of chaetoviridin A 3 from the pyrano-quinone intermediate cazisochromene 8 using the highly-reducing PKS and an acyltransferase.

Armochaetoglobins A–J: Cytochalasan Alkaloids from Chaetomium globosum TW1-1, a Fungus Derived from the Terrestrial Arthropod Armadillidium vulgare

“…This information was supported by the HMBC correlations from H[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and from H-8 to C-23, as well as the 1 H− 1 H COSY spin system of H 2 -20/H 2 -21/H 2 -22.…”

Involvement of Lipocalin‐like CghA in Decalin‐Forming Stereoselective Intramolecular [4+2] Cycloaddition

“…We chose to integrate cghA into the chaetoviridin biosynthetic PKS gene cazM [20] so that the integration event would be indicated by the loss of formation of chaetoviridin A 8 and B 9 . [19] A control experiment verified that disruption of cazM would not affect the production of 1 (Figure 4, i vs. ii).…”

Saccharomyces cerevisiae as a tool for mining, studying and engineering fungal polyketide synthases

“…The resulting yeast strain containing the desired plasmid was then used directly to elucidate the product of the iPKSs through expression of the encoded enzymes and analysis of the resulting products (Mao et al, 2015). Other examples of TAR-based assembly of iPKSs include cazF and cazM from the chaetoviridin biosynthetic gene cluster in Chaetomium globosum (Winter et al, 2015; Winter et al, 2012a); bref-PKS from the biosynthetic gene cluster of brefeldin A in Eupenicillium brefeldianum (Zabala et al, 2014); and fma-PKS from the biosynthetic gene cluster of fumagillin in Aspergillus fumigatus (Lin et al, 2013). A variation of this strategy is to first assemble the entire iPKSs gene using overlap extension PCR (OE-PCR), followed by transformation into yeast along with the vector to yield the intact expression plasmid via recombination.…”

“…Native producers often evolve their own solutions to protect themselves from the presence of toxic compounds, such as specific transporter proteins or other enzymes that confer self-resistance to the native host (Martín et al, 2005). These self-resistance mechanisms can take the form of product-specific transporters like the putative transporter cazK from Chaetomium globosum and the putative efflux pump lovI from A. terreus (Kennedy et al, 1999; Winter et al, 2012b). Recently, Ley et al showed that integration of the putative efflux pump mlcE , from the compactin PKS cluster of P. citrinum, into the S. cerevisiae genome conferred increased resistance to mevastatin, lovastatin, and simvastatin, as compared to the wild type strain.…”