FIGURE 1.

Illustration of bacterial transcription factors (TFs). A transcription factor subunit (denoted as a dumbbell shape) usually contains a regulatory domain and a DNA-binding domain. Normally two subunits dimerize to form a TF which interacts with a bacterial promoter region to either activate or repress transcription initiation. Here, only one activation mode (TF contacts domain 4 of the RNA polymerase σ subunit) and one repression mode (via steric hindrance) were shown to illustrate this process.