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.