High affinity binding site for nuclear factor I next to the hepatitis B virus S gene promoter.

The hepatitis B virus (HBV) surface antigen (HBsAG) is encoded by the S gene under the regulation of a promoter in the pre-S1 region. The S gene promoter does not contain a 'TATA' box-like sequence, but there is a sequence resembling, in part, the late promoter of Simian virus 40 (SV40). In an attempt to study the regulation of the S gene promoter we looked for cellular proteins which bind to this region. We report here that a nuclear protein is tightly bound to the HBV genome at a position approximately 190 bases upstream from the S gene promoter. Evidence is provided to show that (a) this nuclear protein is the nuclear factor I (NF-I) that was previously found to be bound to the inverted terminal repeat of the adenovirus (Ad) DNA and to enhance Ad DNA replication in vitro and (b) this NF-I binding site is required for optimal activity of the S gene promoter.     

In vivo and in vitro analyses of the AmyR binding site of the Aspergillus nidulans agdA promoter; requirement of the CGG direct repeat for induction and high affinity binding of AmyR

The alpha-glucosidase gene (agdA) of Aspergillus nidulans has a single CGGN8CGG type AmyR binding site in its promoter region. The binding site is functional in vivo as a cis-element responsible for induction by starch, and mutational studies indicated that both the CGG triplets are required for high-level induction. A part of AmyR (residues 1-411; AmyR(1-411)), which was produced as a MalE fusion protein in E. coli, bound to the CGGN8CGG site of the agdA promoter. DNA binding profiles to the mutant binding sites that lacked both or either one of the CGG triplets suggested that AmyR(1-411) can bind to a single CGG triplet site with low affinity and that two AmyR molecules cooperatively bind to the CGG direct repeat.