New Antimicrobials Targeting Bacterial RNA Polymerase Holoenzyme Assembly Identified with an in Vivo BRET-Based Discovery Platform.

Bacterial resistance represents a major health threat worldwide and the development of new therapeutics, including innovative antibiotics, is urgently needed. We describe a discovery platform, centered on screening and Bioluminescence Resonance Energy Transfer in yeast cells, for the identification of new antimicrobials that by targeting the protein-protein interaction between the β'-subunit and the initiation factor σ of bacterial RNA polymerase, inhibit holoenzyme assembly and promoter-specific transcription. Out of 34,000 candidate compounds, we identified seven hits capable of interfering with this interaction. Two derivatives of one of these hits proved to be effective in inhibiting transcription in vitro and growth of the Gram-positive pathogens and . Upon supplementation of a permeability-adjuvant, one derivative also effectively inhibited growth. Based on the chemical structures of these inhibitors, we generated a ligand-based pharmacophore model that will guide the rational discovery of increasingly effective antibacterial agents.