title: A "master" in base unpairing during isomerization of a promoter upon RNA polymerase binding.
abstract: Isomerization of a closed to open complex of a promoter upon RNA polymerase binding involves base unpairing at the -10 region. After potassium permanganate sensitivity of unpaired thymine residues, we studied base unpairing at the -10 region during isomerization upon RNA polymerase binding at the P1 and P3 promoters of the gal operon. Substitution of adenine by 2-amino purine (2-AP) at the invariable A small middle dotT base pair at the -11 position of P1 and P3 prevented unpairing not only at that position but also at the other downstream positions, suggesting a "master" role of the adenine base at -11 of the template strand in overall base unpairing. 2-AP at -11 did not inhibit the formation of RNA polymerase small middle dotpromoter complex and subsequent isomerization of the polymerase. Substitution of adenine by 2-AP at several other positions did not affect thymine unpairing. Changing the position of the amino group from C6 in adenine to C2 in 2-AP is mutational only at the master switch position, -11.
authors.affiliation: Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA.
authors.forename: H M
authors.initials: HM
authors.lastname: Lim
authors.forename: H J
authors.initials: HJ
authors.lastname: Lee
authors.forename: S
authors.initials: S
authors.lastname: Roy
authors.forename: S
authors.initials: S
authors.lastname: Adhya
mesh_terms: D020029:Base Pairing; D001483:Base Sequence; D004269:DNA, Bacterial; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D008969:Molecular Sequence Data; D011196:Potassium Permanganate / Q000737:chemistry; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial; D011196:Potassium Permanganate; D012321:DNA-Directed RNA Polymerases