Upstream curved sequences in E. coli are related to the regulation of transcription initiation.

The advancement in Escherichia coli genome research has made the information regarding transcription start sites of many genes available. A study relying on the availability of transcription start locations was performed. The first question addressed was what an average DNA curvature profile upstream of genes would look like when these genes are aligned by transcription start sites in comparison to alignment by translation start sites. Since it was hypothesized that curvature plays a role in transcription regulation, the expectation was that curvature measurements relative to transcription starts, rather than translation, should strengthen the signal. Our study justified this expectation. The second question aimed to clarify the relation between DNA curvature and promoter strength. Through clustering based on DNA curvature profiles along promoter regions, a strong positive correlation between the promoter strength and the curved DNA was found. The third question dealt with dinucleotide periodicity in E. coli to see whether a periodicity pattern specific to promoter regions exists. Such unknown pattern might shed new light on transcription regulation mechanisms in E. coli. A sequence periodicity of about 11 bp is characteristic to the whole E. coli genome, and is especially well-expressed in intergenic regions. Here it was shown that regions of the size of about 100-150 bp centered 70-100 bp upstream to transcription starts carry hidden periodicity with a period of about 10.3 bp.