Sequence distributions associated with DNA curvature are found upstream of strongE. colipromoters

Abstract

The regions upstream from forty-three procaryotic promoters were examined for nucleotide distributions which have been associated with DNA curvature. The analysis procedure assigned a DNA curvature score based on the phasing of the 5′ and 3′ ends of A_n and T_n tracts, n ≥ 3. The weighting scheme for the curvature score was based on recent studies which showed that tracts of A_n and T_n periodically phased with the helix repeat cause DNA curvature. Results snow that promoters which have high transcription initiation rates in vivo tend to have high curvature scores in their upstream regions. Regions downstream from the transcription startpoint do not have sequences correlated with DNA curvature. Four promoters which have been shown to have upstream activation regions have curvature scores above 1.5 in their −40 to −150 regions. The correlations observed lend support to the hypothesis that DNA curvature is associated with upstream activation of transcription.