Isolation and Characterization of the gtfA Gene Encoding GAL4-Like Transcription Factor in Aspergillus nidulans

ABSTRACT Polyketide synthases (PKSs) and/or nonribosomal peptide synthetases (NRPSs) are central components of secondary metabolism in bacteria, plants, and fungi. In filamentous fungi, diverse PKSs and NRPSs participate in the biosynthesis of secondary metabolites such as pigments, antibiotics, siderophores, and mycotoxins. However, many secondary metabolites as well as the enzymes involved in their production are yet to be discovered. Both PKSs and NRPSs require activation by enzyme members of the 4′-phosphopantetheinyl transferase (PPTase) family. Here, we report the isolation and characterization of Aspergillus nidulans strains carrying conditional (cfwA2) and null (ΔcfwA) mutant alleles of the cfwA gene, encoding an essential PPTase. We identify the polyketides shamixanthone, emericellin, and dehydroaustinol as well as the sterols ergosterol, peroxiergosterol, and cerevisterol in extracts from A. nidulans large-scale cultures. The PPTase CfwA/NpgA was required for the production of these polyketide compounds but dispensable for ergosterol and cerevisterol and for fatty acid biosynthesis. The asexual sporulation defects of cfwA, ΔfluG, and ΔtmpA mutants were not rescued by the cfwA-dependent compounds identified here. However, a cfwA2 mutation enhanced the sporulation defects of both ΔtmpA and ΔfluG single mutants, suggesting that unidentified CfwA-dependent PKSs and/or NRPSs are involved in the production of hitherto-unknown compounds required for sporulation. Our results expand the number of known and predicted secondary metabolites requiring CfwA/NpgA for their biosynthesis and, together with the phylogenetic analysis of fungal PPTases, suggest that a single PPTase is responsible for the activation of all PKSs and NRPSs in A. nidulans.

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A Chimeric Subunit of Yeast Transcription Factor IIIC Forms a Subcomplex with τ95

Molecular and Cellular Biology ◽

10.1128/mcb.18.6.3191 ◽

1998 ◽

Vol 18 (6) ◽

pp. 3191-3200 ◽

Cited By ~ 25

Author(s):

Nathalie Manaud ◽

Rosalía Arrebola ◽

Bénédicte Buffin-Meyer ◽

Olivier Lefebvre ◽

Hartmut Voss ◽

...

Keyword(s):

Transcription Factor ◽

Essential Gene ◽

Cell Metabolism ◽

Chimeric Protein ◽

Gene Encoding ◽

Multifunctional Protein ◽

Isolation And Characterization ◽

Promoter Recognition ◽

Transcription Factor Iiib

ABSTRACT The multisubunit yeast transcription factor IIIC (TFIIIC) is a multifunctional protein required for promoter recognition, transcription factor IIIB recruitment, and chromatin antirepression. We report the isolation and characterization of TFC7, an essential gene encoding the 55-kDa polypeptide, τ55, present in affinity-purified TFIIIC. τ55 is a chimeric protein generated by an ancient chromosomal rearrangement. Its C-terminal half is essential for cell viability and sufficient to ensure TFIIIC function in DNA binding and transcription assays. The N-terminal half is nonessential and highly similar to a putative yeast protein encoded on another chromosome and to a cyanobacterial protein of unknown function. Partial deletions of the N-terminal domain impaired τ55 function at a high temperature or in media containing glycerol or ethanol, suggesting a link between PolIII transcription and metabolic pathways. Interestingly, τ55 was found, together with TFIIIC subunit τ95, in a protein complex which was distinct from TFIIIC and which may play a role in the regulation of PolIII transcription, possibly in relation to cell metabolism.

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