The ban operon of bacteriophage P1. Localization of the promoter controlled by P1 repressor

Repression of a strong promoter localized 5' to the P1 ban gene is a prerequisite for cloning the ban operon in the multicopy plasmid pBR325. Repression is brought about by the binding of P1 repressor to the operator of the ban operon (Heisig, A., Severin, I., Seefluth, A. K., and Schuster, H. (1987) Mol. Gen. Genet. 206, 368-376). Binding of RNA polymerase in vitro overlaps with the operator and is inhibited by P1 repressor as shown by electron microscopy. The mutant P1 bac, which renders ban expression constitutive, contains a single base pair exchange within the operator. As a consequence, more repressor is required (i) for the inhibition of binding of RNA polymerase, and (ii) for the electrophoretic retardation of a P1 bac DNA fragment when compared to the corresponding bac+ fragment. A P1 ban recombinant plasmid containing a 4-base pair deletion close to the operator still allows binding of repressor but not of RNA polymerase. By that means, a repressible promoter is located at the P1 map position 72 in a distance of about 2.5 kilobase pairs to the beginning of the ban gene.     

Heat shock elements are involved in heat shock promoter activation during tobacco seed maturation

The soybean Gmhsp17.3-B heat shock promoter is developmentally regulated in transgenic tobacco, as indicated by the constitutive expression of a -glucuronidase reporter in seeds [16]. In this paper, we show that both the heat shock promoter-driven -glucuronidase activity and the mRNA of the endogenous Nthsp18P gene accumulate coincident with the onset of seed desiccation. Deletions of the soybean Gmhsp17.3-B promoter, encompassing the heat shock element (HSE)-containing regions, revealed a co-localization of sequences responsible for heat induction and developmental expression. Moreover, synthetic HSEs fused to a TATA box sequence had the potential to stimulate the developmental expression of a GUS reporter gene in seeds of transgenic plants.