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J. Biol. Chem. 286 (39): 34071-34081

© 2011 by The American Society for Biochemistry and Molecular Biology, Inc.

Background: Disulfide bond formation regulates nuclear localization of transcription factor Yap1.

Results: Levels of Yap1-binding protein Ybp1 control cytoplasmic oxidative protein folding.

Conclusion: Oxidative stress response limited by levels of protein folding cofactor rather than its transcriptional regulator target.

Significance: Oxidative protein folding is the key step in oxidative stress response in fungi.

Differential Oxidant Tolerance Determined by the Key Transcription Factor Yap1 Is Controlled by Levels of the Yap1-binding Protein, Ybp1*

Kailash Gulshan{ddagger}, Stella S. Lee§1, , and W. Scott Moye-Rowley{ddagger}2

From the §Molecular Biology Program and
{ddagger}Department of Molecular Physiology and Biophysics, Carver College of Medicine, University of Iowa, Iowa City, 52242

ABSTRACT Back to Top

Abstract: The Saccharomyces cerevisiae transcription factor Yap1 is a central determinant of oxidative stress tolerance. This protein is found primarily in the cytoplasm in the absence of oxidative stress but, upon exposure to oxidants, rapidly translocates to the nucleus and activates expression of target genes. Although both diamide and H2O2 have been used to impose oxidative stress on cells, these different oxidants trigger Yap1 nuclear localization in distinctly different ways. Diamide appears to oxidize particular cysteine residues on Yap1, leading to inhibition of association of Yap1 with the nuclear exportin Crm1. Crm1 would normally transport Yap1 out of the nucleus. H2O2 activation of Yap1 nuclear localization requires the participation of the glutathione peroxidase Gpx3 and the Yap1-binding protein Ybp1. H2O2 exposure triggers formation of a dual disulfide bonded Yap1 that is catalyzed by the presence of Gpx3 and Ybp1. In the current study, we have determined that two distinct pools of Yap1 exist in the cell. These pools are designated by the level of Ybp1. Ybp1 interacts directly with Yap1 and these proteins form a stable complex in vivo. Genetic and biochemical experiments indicate that Ybp1 is rate-limiting for Yap1 oxidative folding during H2O2 stress. The fungal pathogen Candida glabrata expresses a protein homologous to Ybp1 called CgYbp1. Overproduction of CgYbp1 elevated H2O2 tolerance in this pathogen indicating that the determinative role of Ybp1 in setting the level of H2O2 resistance has been evolutionarily conserved.

Key Words: Nuclear Translocation • Oxidative Stress • Protein Folding • Reactive Oxygen Species (ROS) • Transcription Factors • Transcription Regulation

Received for publication April 14, 2011. Revision received August 11, 2011.

FOOTNOTES Back to Top

1 Present address: Program in Human Genetics, Johns Hopkins University School of Medicine, 733 N. Broadway, BRB 515, Baltimore, MD 21205.

2 To whom correspondence should be addressed: 6-530 Bowen Science Bldg., University of Iowa, Iowa City, IA 52242. Tel.: 319-335-7874; Fax: 319-335-7330; E-mail: scott-moye-rowley{at}uiowa.edu.

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