The effects of mutations in the ant promoter of phage P22 depend on context.
Recombination was used to construct 22 two- or three-way combinations of down- and up-mutations in Pant, a strong, near-consensus promoter of phage P22. The relative strengths of these promoters in vivo were assayed by fusing them to an ant/lacZ gene fusion and measuring beta-galactosidase levels produced by lysogens carrying the fusions on single-copy prophages. The results of these assays show that the magnitude of the effect of a promoter mutation can vary considerably when its context is changed by the presence of another mutation. In addition, as Pant approaches conformity with the consensus promoter sequence, the up-mutations decrease promoter strength, even though the same mutations increase promoter strength in the presence of a down-mutation. These context effects imply that individual consensus base pairs cannot be considered to contribute to promoter strength independently.
D001483:Base Sequence; D003001:Cloning, Molecular; D005814:Genes, Viral; D009154:Mutation; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011995:Recombination, Genetic; D012483:Salmonella Phages / Q000235:genetics*; D001616:beta-Galactosidase / Q000032:analysis
D001616:beta-Galactosidase