Diagram of the GAL cluster and the GAL7
promoter. (A) Diagram showing the arrangement of the
structural GAL genes. GAL10 and
GAL7 are contained within YC10-7. Deletions of the
GAL10 poly(A) site result in Δ-55 and Δ-75,
respectively. YC10-7 gives rise to monocistronic GAL10
and GAL7 mRNA, respectively (dotted lines below), and is
viable on gal medium (Gal+). Δ-55 and Δ-75 give rise to bicistronic
mRNA, which does not produce GAL7 mRNA, and are
therefore gal sensitive (Gal−). Black boxes represent Gal4p-binding
sites. (B) Schematic of the region 260 bp upstream of
the GAL7 transcription initiation site (+1). The TATA
box and the two Gal4p binding sites are shown (dark boxes); the
distances between these elements are indicated below. Also shown are
the positions of primers used for in vivo footprinting
(P1–P4). (C) Sequences of the two Gal4p binding sites
(GAL4-1 and GAL4-2). The center of the roughly symmetrical 17-bp sites
is indicated by a vertical, dashed line. The base pairs are numbered
sequentially from the center; the central base pair has been assigned
the number 0. The protected guanines of the highly conserved outer
triplet are in bold and indicated by horizontal bars. They are shown in
uppercase and lowercase, depending on the degree of protection. Also
indicated are the primers (P1–P4), which were used to visualize the
particular strand.