The network of transcriptional interactions imposes linear constrains in the genome.

Two prokaryotic organisms for which transcriptional regulatory interactions have been well elucidated by experimental means are Escherichia coli and Bacillus subtilis. Here we show, with the help of simulations and from known data, the importance of proximity of the transcription factor gene and the respective regulated gene in regulatory networks. We discuss the importance of the location of external sensing machinery close to the genes for transcription factors that regulate them in light of our finding.