A phage repressor involved in the DNA-damage response of Francisella

Despite the critical importance of the diseases caused by members of the genus Francisella, the DNA repair mechanisms of this pathogen remain understudied. In this work, the transcriptional response of Francisella hispaniensis to the DNA-damaging agent ciprofloxacin was studied using RNA sequencing.

Among the differentially expressed genes, we identified a S24 family peptidase-encoding gene. Electrophoretic mobility shift assays demonstrated that the product of this gene specifically binds to the palindromic sequence GTG-N11-CAC present in its promoter region, resulting in autoregulation. In silico analyses revealed that this S24 peptidase, here termed FddR, is most likely a co-opted phage repressor that implements a DNA-damage response across the Francisella genus.