When a transcription factor binds to a specific promoter, it can either activate or repress transcription [35, 43, 44]. To investigate the possible modulatory role of E. chaffeensis proteins on transcription of promoters of two differentially expressed genes, p28-Omp14 and p28-Omp19, we prepared E. chaffeensis whole-cell protein lysate from macrophage-derived bacteria and evaluated its effect on transcription in vitro. Addition of the macrophage cell infection-derived E. chaffeensis protein extracts resulted in enhanced transcription suggesting

CHIR-99021 research buy that promoters of the p28-Omp14 and p28-Omp19 genes may be regulated in response to changing environments of the pathogen. Importantly, the enhanced in vitro transcription observed in this study in response to addition of protein extracts suggests that the lysates contain transcription regulators. Given the differential expression

of p28-Omp14 and p28-Omp19 genes [15] in vertebrate and invertebrate hosts, the hypothesis that promoters of these genes may be under both positive and negative regulation in response to the changing host environments is also plausible. This hypothesis requires OICR-9429 mouse additional investigations, including the evaluation of the impact of tick cell environment. As an organism may express diverse array of transcription factors, it is highly likely that E. chaffeensis may regulate its gene expression via modulating the expression of transcription factors in support of maintaining Cobimetinib supplier its existence in dual hosts. Transcription regulation of a gene is a dynamic process and is responsive to environmental cues under which TFs trigger regulation [39, 45–47]. This study shows the first evidence of stimulatory effect of E. chaffeensis whole-cell protein extract on the transcription of both p28-Omp14 and p28-Omp19 promoters in vitro. In our previous studies, we reported that the expression levels of the p28-Omp14 and p28-Omp19 genes are different in macrophage and tick cell environments [16, 19]. Although both the genes are transcriptionally active in macrophage host cell environment under in vitro and in vivo

conditions, the expression levels for p28-Omp19 is higher for the bacteria in infected macrophages, whereas in tick cells Fossariinae p28-Omp14 is the predominantly expressed protein [16, 19]. Consistent with those observations, the promoter constructs of both p28-Omp14 and p28-Omp19 genes remained active and enhanced when E. chaffeensis protein lysates prepared from macrophage culture derived organisms were added. Additional investigations are needed to further define the differences in the expression levels for the p28-Omp14 and p28-Omp19 genes in macrophage and tick cell environments. A gene in a cell may be regulated by different TFs, and the contribution from different TFs may be variable under different environmental conditions [48].