Abstract
Transcription factors are key regulatory proteins in all living beings. In fungi, transcription factors include either broad-domain regulatory proteins that affect the expression of many genes involved in biosynthetic processes, or proteins encoded by cluster-associated (also called pathway-specific) regulatory genes. Belonging to the most interesting transcription factors in fungi are binuclear zinc finger proteins. In addition to the transcription factors in the strict sense, other proteins play a very important role in the expression of genes for primary and secondary metabolism in fungi, such as winged helix regulators, the LaeA protein and the velvet complex. LaeA appears to be involved in heterochromatin reorganization, and the velvet complex proteins, which are nuclear factors that associate with LaeA, also have a determining role in both differentiation (sporulation) and secondary metabolite biosynthesis. The genes involved in the biosynthesis of β-lactam antibiotics are well known and serve as an excellent model to understand the transcriptional control of genes involved in the biosynthesis of secondary metabolites. Interaction between different regulatory proteins in the promoter regions may represent a cross-talk regulation between different gene clusters.
Highlights
Fungi play very important roles in nature
Unlike in P. chrysogenum, catabolite regulation (CreA) seems not to play a role in C-source repression of β-lactam biosynthesis in A. nidulans, since different mutants in CreA, CreB, or CreC did not modify carbon regulation of penicillin biosynthesis [29,103,104]. These results indicate that a CreA-independent mechanism of carbon repression controls penicillin biosynthesis in A. nidulans
There are many transcription factors that affect the expression of genes involved in primary and secondary metabolism in filamentous fungi
Summary
Fungi play very important roles in nature. They are crucial in biotransformation in the biosphere, acting as recyclers and playing a major role in the balance of ecosystems. Transcriptional control of genes involved in the biosynthesis of secondary metabolites is carried out by two categories of transcription factors that interact with distinct recognition sequences (target sequences) present in the promoter regions of different genes. These transcription factors can be regulatory proteins that are specific to a particular gene cluster, or broad-domain transcription factors that are mediated by nutritional and environmental signals such as carbon source, pH, or nitrogen sources. Cephalosporin C biosynthesis in A. chrysogenum requires the epimerization of isopenicillin N to penicillin N in a reaction catalyzed by the products of the cefD1 and cefD2 genes This is followed by thiazolidine ring expansion and further hydroxylation by means of the bifunctional protein encoded.
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