title: Long W tracts are over-represented in the Escherichia coli and Haemophilus influenzae genomes.
abstract: The occurrence of DNA tracts of the three binary base combinations: R.Y, K.M and W;S has been mapped in the complete genomes of Haemophilus influenzae and Escherichia coli. A highly significant over-representation of W tracts is observed in both bacteria. The excess of W tracts is particularly striking in the 10% intercoding regions. Subdivision of intercoding regions into divergent (promoting), convergent (terminating) and sequential subregions shows that the excess of W tracts is most concentrated in the promoter regions. A particularly high excess of W tracts is observed in the first 200 bases 5' upstream of coding start sites. The data suggest that W tracts have a role in promoter function. A function as unwinding centers, analogous to the role of R.Y tracts in eukaryotes, is proposed. R.Y and K.M tracts are only modestly over-represented in the two bacteria.
authors.affiliation: The European Bioinformatics Institute, Hinxton, Cambridge, UK.
authors.forename: B
authors.initials: B
authors.lastname: Shomer
authors.forename: G
authors.initials: G
authors.lastname: Yagil
mesh_terms: D020029:Base Pairing; D004269:DNA, Bacterial / Q000032:analysis / Q000737:chemistry*; D004926:Escherichia coli / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D006193:Haemophilus influenzae / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000502:physiology; D016364:Reading Frames / Q000235:genetics; D012984:Software
chemical_list: D004269:DNA, Bacterial