The Transcriptional Architecture of Bacterial Biosynthetic Gene Clusters

Bacterial biosynthetic gene clusters (BGCs) drive the production of diverse bioactive specialized metabolites regulated by transcription factors (TFs) in response to environmental signals. In this meta-analysis, we investigated the regulatory architecture of BGCs by compiling experimental data sets of transcription factor binding sites (TFBSs) to unveil (i) the functional gene categories preferentially targeted by TFs, (ii) the transcriptional coverage based on cluster organization, (iii) the positional distribution of TFBSs, and (iv) the binding strength of TFs. Our analysis reveals a strategy where global TFs primarily target monocistronic pathway-specific TFs when present, aligning with a "one-for-all" strategy ensuring cluster-wide expression control. In contrast, biosynthetic genes are typically organized into polycistronic operons, promoting the synchronized production of building blocks, core structures, and modifications. Assessment of the TF-TFBS interaction strength indicates that TFBSs within BGCs exhibit lower binding affinities compared to those associated with core regulon genes outside BGCs. This lower binding affinity allows greater regulatory flexibility, as BGC expression often responds to multiple environmental signals, each one sensed by its specific TF. These findings refine our understanding of the regulatory logic shaping BGC expression and offer valuable insights for predicting activation conditions, facilitating the discovery of novel compounds through targeted culture and engineering strategies.