Orateur
Description
DNA supercoiling acts as a global and ancestral transcriptional regulator in bacteria, that plays an important role in adapting their expression program to environmental changes, but for which no quantitative or even qualitative regulatory model is available. I will present two quantitative thermodynamic models of (1) promoter binding by the RNA Polymerase and (2) promoter opening during transcription initiation, which show how bacterial cells can globally and selectively activate subsets of their promoters by adjusting their topological level, depending on the promoter structures. This regulation mode is based on the basal interaction betweel RNA Polymerase and the promoter elements, independently of any additional transcriptional regulator, and is therefore relevant to all bacterial species. To demonstrate this ancestral role, I will show that our models are predictive of the global transcriptional response to antibiotics-induced DNA relaxation in a wide range of evolutionarily distant organisms, as well as the modifications in gene expression observed in a long-time evolution experiment with Escherichia coli.
