poses a great threat in healthcare settings worldwide with clinical isolates displaying an ever-evolving multidrug-resistance. In strains of , expression of multiple error-prone polymerase genes is co-repressed by UmuDAb, a member of the LexA superfamily, and a small protein, DdrR. It is currently unknown how DdrR establishes this repression. Here, we use surface plasmon resonance spectrometry to show that DdrR forms a stable complex with the UmuDAb regulator. Our results indicate that the carboxy-terminal dimerization domain of UmuDAb forms the interaction interface with DdrR. Our data also show that RecA-mediated inactivation of UmuDAb is inhibited when this transcription factor is bound to its target DNA. I... More
poses a great threat in healthcare settings worldwide with clinical isolates displaying an ever-evolving multidrug-resistance. In strains of , expression of multiple error-prone polymerase genes is co-repressed by UmuDAb, a member of the LexA superfamily, and a small protein, DdrR. It is currently unknown how DdrR establishes this repression. Here, we use surface plasmon resonance spectrometry to show that DdrR forms a stable complex with the UmuDAb regulator. Our results indicate that the carboxy-terminal dimerization domain of UmuDAb forms the interaction interface with DdrR. Our data also show that RecA-mediated inactivation of UmuDAb is inhibited when this transcription factor is bound to its target DNA. In addition, we show that DdrR interacts with a putative prophage repressor, homologous to LexA superfamily proteins. These data suggest that DdrR modulates DNA damage response and prophage induction in by binding to LexA-like regulators. We previously identified a 50-residue bacteriophage protein, gp7, which interacts with and modulates the function of the LexA transcription factor from . Here we present data that indicates that the small DdrR protein from likely coordinates the SOS response and prophage processes by also interacting with LexA superfamily members. We suggest that similar small proteins that interact with LexA-like proteins to coordinate DNA repair and bacteriophage functions may be common to many bacteria that mount the SOS response.
