A comparative evolutionary study of transcription networks. The global role of feedback and hierachical structures

We present a comparative analysis of large-scale topological and evolutionary properties of transcription networks in three species: the two distant bacteria E. coli and B. subtilis, and the yeast S. cerevisiae. The study focuses on the global aspects of feedback and hierarchy in transcriptional regulatory pathways. While confirming that gene duplication has a significant impact on the shaping of all the analyzed transcription networks, our results point to distinct trends between the bacteria, which display a hierarchical network structure with short transcription cascades, and yeast, which seems able to sustain a higher wiring complexity, including larger feedback, longer transcription cascades, and the combinatorial use of heterodimers made of duplicate transcription factors, absent in E. coli.