Adaptation to stress conditions during Francisella infection: the role of HU protein

Although HU proteins are generally considered to bind preferentially to distorted DNA structures rather than specific DNA sequence motifs, their binding properties may vary depending on environmental conditions. Here, using ChIP-seq, we identified the DNA-binding motif of the Francisella tularensis HU protein (FtHU) during intracellular growth.

The motif closely resembled that we previously identified under oxidative stress conditions, suggesting a conserved DNA-binding preference of FtHU under different stress conditions. Among the identified FtHU targets were the dnaK and groEL genes, which encode strongly immunogenic chaperone proteins, and the region upstream of FTS_0923. Deletion of the hupB gene resulted in reduced transcription levels of dnaK, groEL, and FTS_0923, indicating that FtHU contributes to their transcriptional regulation during intracellular growth in mouse bone marrow-derived macrophages.