Figure 10.

Oxidative stress signaling pathways that lead to transcription of the ctt1⁺ gene. A multistep phosphorelay composed of an unknown sensor kinase, Mpr1, and the Mcs4 response regulator transmits oxidative stress signals to the Spc1 MAPK cascade. Oxidative stress induces partial activation of Spc1 even in the Δmcs4 Δmpr1 strain, suggesting that oxidative stress can be transmitted to the Spc1 cascade by additional pathways. Activated Spc1 induces transcription of ctt1⁺ and other stress-response genes through the Atf1 transcription factor. The Pap1 transcription factor can also mediate ctt1⁺ expression in response to oxidative stress independently of the Spc1 pathway.