H ₂ O ₂ Activates the Nuclear Localization of Msn2 and Maf1 through Thioredoxins in Saccharomyces cerevisiae

Abstract

The cellular response to hydrogen peroxide (H 2 O 2 ) is characterized by a repression of growth-related processes and an enhanced expression of genes important for cell defense. In budding yeast, this response requires the activation of a set of transcriptional effectors. Some of them, such as the transcriptional activator Yap1, are specific to oxidative stress, and others, such as the transcriptional activators Msn2/4 and the negative regulator Maf1, are activated by a wide spectrum of stress conditions. How these general effectors are activated in response to oxidative stress remains an open question. In this study, we demonstrate that the two cytoplasmic thioredoxins, Trx1 and Trx2, are essential to trigger the nuclear accumulation of Msn2/4 and Maf1, specifically under H 2 O 2 treatment. Contrary to the case with many stress conditions previously described for yeast, the H 2 O 2 -induced nuclear accumulation of Msn2 and Maf1 does not correlate with the downregulation of PKA kinase activity. Nevertheless, we show that PP2A phosphatase activity is essential for driving Maf1 dephosphorylation and its subsequent nuclear accumulation in response to H 2 O 2 treatment. Interestingly, under this condition, the lack of PP2A activity has no impact on the subcellular localization of Msn2, demonstrating that the H 2 O 2 signaling pathways share a common route through the thioredoxin system and then diverge to activate Msn2 and Maf1, the final integrators of these pathways.

Role of the Yap Family in the Transcriptional Response to Oxidative Stress in Yeasts

“…For example, the gene TRX2 is a highly conserved oxydoreductase, required to maintain the redox homeostasis of the cell. In S. cerevisiae, thioredoxin TRX2 and thioredoxin reductase TRR1 were shown to be necessary to protect the cell against oxidative stress induced by the presence of ROS compounds in condition H 2 O 2 (Boisnard et al, 2009) or exposure to dithiothreitol (DTT) (Garrido and Grant, 2002). This agrees with the review of Rodrigues-Pousada et al (2010), in which Yap2p and Yap4p were described as involved in several types of stress responses, including oxidative stress (Cohen et al, 2002;Nevitt et al, 2004).…”

The Response to Heat Shock and Oxidative Stress inSaccharomyces cerevisiae

“…This observation, coupled with the large number of oxidative stress genes under Msn2/Msn4 control, suggests that these factors are responsive to oxidant challenge. Recent experiments have directly examined the localization of Msn2/4 to the nucleus upon oxidative stress (Boisnard et al 2009). Interestingly, important differences with other stress-stimulated nuclear localization have been detected.…”

tRNA biology charges to the front

“…Earlier studies had implicated Tpd3, a regulatory subunit of the TORdependent protein phosphatase PP2A, in tRNA transcription (van Zyl et al 1992), and it has since been learned that Maf1 remains phosphorylated in PP2A mutants (Boisnard et al 2009), showing that PP2A is a phosphatase acting on Maf1.…”

“…Maf1 is dephosphorylated in response to conditions that slow growth-nutrient deprivation, shift from fermentation to respiration carbon sources, DNA damage, and various other environmental stresses (Boisnard et al 2009; for review, see Willis and Moir 2007;Ciesla and Boguta 2008)-and unphosphorylated Maf1 is able to negatively regulate Pol III transcription. Earlier studies had implicated Tpd3, a regulatory subunit of the TORdependent protein phosphatase PP2A, in tRNA transcription (van Zyl et al 1992), and it has since been learned that Maf1 remains phosphorylated in PP2A mutants (Boisnard et al 2009), showing that PP2A is a phosphatase acting on Maf1.…”