title: Multiple transitions to non-B-DNA structures occur in the distal regulatory region of the rat prolactin gene.
abstract: The developmentally regulated rat prolactin (rPRL) gene presents a promising model system toward understanding the biological role of non-B-DNA structural elements. Two predominantly alternating purine-pyrimidine (APP) (dA-dC)n.(dG-dT)n repeats of 58 and 178 base-pairs flank the (A + T)-rich distal regulatory region. We have characterized several transitions to non-B-DNA structures within this region in negatively supercoiled plasmids by utilizing high resolution chemical probing. Each repeat undergoes a full-length conversion to a novel left-handed helical structure via the stepwise nucleation and propagation of discrete "segments". These segments are delimited by out-of-alternation bases that are susceptible to attack by potassium permanganate and thus appear to be significantly unstacked within the left-handed helices. Moreover, the spatial order of successive right- to left-handed DNA transitions within each repeat exhibits a clear polarity toward the distal regulatory region of the rPRL gene. An additional transition involving the long-range unpairing of (A + T)-rich sequences establishes a directional propagation toward the regulatory region. These data demonstrate a complex series of quasi-independent transitions to non-B-DNA structures that impinge upon a known regulatory control region.
authors.affiliation: Department of Biochemistry, University of Wisconsin, Madison 53706.
authors.forename: M P
authors.initials: MP
authors.lastname: Kladde
authors.forename: J
authors.initials: J
authors.lastname: D'Cunha
authors.forename: J
authors.initials: J
authors.lastname: Gorski
mesh_terms: D000818:Animals; D001482:Base Composition; D001483:Base Sequence; D004247:DNA / Q000737:chemistry*; D004256:DNA Polymerase I / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011388:Prolactin / Q000235:genetics*; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid; D012091:Repetitive Sequences, Nucleic Acid
chemical_list: D004277:DNA, Single-Stranded; D011388:Prolactin; D004247:DNA; D004256:DNA Polymerase I