FIGURE 9:
The transcription factor Sko1 cooperates with Hot1 for efficient transcription of STL1 but is not essential for it. (A) Induction of STL1-LacZ reporter genes is reduced in sko1∆ cells. The indicated reporter genes were introduced into cells of the BY4741 and sko1∆ strains. The β-galactosidase activity in these cells was monitored before and after exposure to 0.7 M NaCl. (B) Sko1 has no effect on steady-state levels of Hog1 and Hot1 as monitored by Western blot analysis of cell lysates prepared from the indicated strains. Note that levels of Hot1 were monitored using anti-HA antibodies in strains harboring a single-copy plasmid carrying the HOT1 gene with its native promoter. Lysate of hog1∆ cells was used as a control for the anti-Hog1 antibody. (C) A putative binding site for Sko1 is found (dashed line) in the STL1 promoter within the region containing the HoRE (upper sequence). The lower sequence shows the fragment deleted in the construct 704STL1delSKO1-LacZ. Bottom, β-galactosidase activity of cells (BY4741 and sko1∆) harboring this reporter and the other indicated reporters.