The transcription factor Pap1 regulates antioxidant-gene transcription in response to H2O2 [1]. This region is cysteine rich. Alkylation of cysteine residues following treatment with a cysteine alkylating agent can mask the accessibility of the nuclear exporter Crm1, triggering nuclear accumulation and Pap1 dependent transcriptional expression [2].

1: A cysteine-sulfinic acid in peroxiredoxin regulates H2O2-sensing by the antioxidant Pap1 pathway. Vivancos AP, Castillo EA, Biteau B, Nicot C, Ayte J, Toledano MB, Hidalgo E; Proc Natl Acad Sci U S A. 2005;102:8875-8880. PMID:15956211

2: Diethylmaleate activates the transcription factor Pap1 by covalent modification of critical cysteine residues. Castillo EA, Ayte J, Chiva C, Moldon A, Carrascal M, Abian J, Jones N, Hidalgo E; Mol Microbiol. 2002;45:243-254. PMID:12100563