FIG. 1.

Strategy of the genetic screen. (A) In wild-type cells, Wis1 overexpression leads to hyperactivation of Spc1, which causes cellular lethality through Atf1 and an unknown factor. (B) In Δatf1 mutant cells, Spc1 activated by Wis1 overexpression brings about cellular lethality through an unknown factor. (C) The toxicity of Wis1 overexpression is expected to be suppressed in mutants defective in (i) the unknown target of Spc1 MAPK or (ii) factors required for activity and/or function of Spc1 MAPK.