FIG. 2.

PTC1, PTC2, and PTC3 suppress growth defects due to Hog1 hyperactivation. Deletion of SLN1 hyperactivates the downstream MAPK cascade and is lethal. Expression of PTC1, PTC2, and PTC3 from multicopy plasmids suppressed lethality of the sln1Δ strain, while overexpression of the metal binding site mutations ptc1D58N, ptc2D62N, and ptc3D62N did not. The ability of PTCs and their mutant counterparts to suppress sln1Δ lethality was examined using the 5-FOA assay. IMY101, the sln1Δ strain bearing pSLN1(URA3), a CEN-based plasmid expressing the SLN1 and URA3 genes, was transformed with multicopy plasmids bearing wild-type (wt) PTC genes (pPTC1, pPTC2, and pPTC3), mutant PTCs (pPTC1D58N, pPTC2D62N, and pPTC3D62N), or empty vector (YEplac181). The transformants were patched on synthetic medium lacking leucine and containing 5-FOA and then examined for growth after 3 days at 30°C.