Figure 9.

Pap1 can regulate ctt1⁺ expression upon oxidative stress independently of the Spc1 pathway. (A) Wild-type (PR109), wis1DD (KS2081), and wis1DD Δpap1 (CA356) strains were grown to midlog phase in YES medium at 30°C and treated with 0.3 mM H₂O₂. Aliquots of cells were harvested at the indicated times for Northern hybridization analysis with the ctt1⁺ and leu1⁺ probes. In wis1DD cells, which have constitutive Spc1 activity, ctt1⁺ induction upon oxidative stress was dependent on Pap1. (B) Northern analysis similar to that described for A was performed with Δatf1 (KS1497), Δatf1 Δpap1 (CA334), and Δatf1 Δspc1 (KS1533). In the Δatf1 background, the induction of ctt1⁺ upon oxidative stress was dependent on Pap1 but not Spc1.