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Eukaryotic Cell, May 2009, p. 768-778, Vol. 8, No. 5
1535-9778/09/$08.00+0     doi:10.1128/EC.00021-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Oxidative Stress Function of the Saccharomyces cerevisiae Skn7 Receiver Domain{triangledown}

Xin-Jian He,{dagger} KariAn E. Mulford, and Jan S. Fassler*

Department of Biology, University of Iowa, Iowa City, Iowa 52242

Received 15 January 2009/ Accepted 10 March 2009

The bifunctional Saccharomyces cerevisiae Skn7 transcription factor regulates osmotic stress response genes as well as oxidative stress response genes; however, the mechanisms involved in these two types of regulation differ. Skn7 osmotic stress activity depends on the phosphorylation of the receiver domain aspartate, D427, by the Sln1 histidine kinase. In contrast, D427 and the SLN1-SKN7 phosphorelay are dispensable for the oxidative stress response, although the receiver domain is required. The majority of oxidative stress response genes regulated by Skn7 also are regulated by the redox-responsive transcription factor Yap1. It is therefore possible that the nuclearly localized Skn7 does not itself respond to the oxidant but simply cooperates with Yap1 when it translocates to the nucleus. We report here that oxidative stress leads to a phosphatase-sensitive, slow-mobility Skn7 variant. This suggests that Skn7 undergoes a posttranslational modification by phosphorylation following exposure to oxidant. Oxidant-dependent Skn7 phosphorylation was eliminated in strains lacking the Yap1 transcription factor. This suggests that the phosphorylation of Skn7 is regulated by Yap1. Mutations in the receiver domain of Skn7 were identified that affect its oxidative stress function. These mutations were found to compromise the association of Yap1 and Skn7 at oxidative stress response gene promoters. A working model is proposed in which the association of Yap1 with Skn7 in the nucleus is a prerequisite for Skn7 phosphorylation and the activation of oxidative stress response genes.

* Corresponding author. Mailing address: Department of Biology, University of Iowa, Iowa City, IA 52242. Phone: (319) 335-1542. Fax: (319) 335-1069. E-mail: jan-fassler{at}uiowa.edu

{triangledown} Published ahead of print on 20 March 2009.

{dagger} Present address: Department of Botany and Plant Sciences, University of California, Riverside, CA 92521.

Eukaryotic Cell, May 2009, p. 768-778, Vol. 8, No. 5
1535-9778/09/$08.00+0     doi:10.1128/EC.00021-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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