Regulation of ϕX174 gene transcription. Gene transcription in ϕX174 is regulated by four promoters (PA, PB, PD, *) and four transcription terminators (TJ, TF, TG, TH). Bars indicate transcript start and stop and thickness of bars indicates relative amount of transcript. Ovals show approximate positions of sequences detected in qPCR experiments. Gene locations are shown below, and genes B, K and E are in different reading frames from the genes with which they overlap. The ϕX174 genome is a circular molecule; the figure was linearized for clarity. From [21, 22].