FIGURE 5.
The topology-dependent transcription of Pccat is dependent on its chromosomal location. (A) Organization of the S. pneumoniae R6 chromosome in topological domains. Circles, from outside to inside, represent: % GC (values above the average in purple); DNA topoisomerase genes (dark blue curved arrows); topology-responsive domains. The chromosome is organized into domains up-regulated (U, red boxes) or down-regulated (D, blue boxes) in response to DNA relaxation, and ATr domains (green boxes). (B) Transcriptional response to DNA relaxation by NOV measured by qRT–PCR. A Ptccat cassette, coding for chloramphenicol-acetyl-transferase, which carries its own promoter (curved arrow) and is flanked by two transcriptional terminators (stem and loop structures), was inserted into different supercoiling domains. Cultures of the R6-CAT strains were treated with NOV and the transcription of cat analyzed by qRT–PCR. Taken from Ferrándiz et al. (2014), with modifications.