MCB
Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Copyright Information
Right arrow Books from ASM Press
Right arrow MicrobeWorld
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Zhang, D. D.
Right arrow Articles by Hannink, M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Zhang, D. D.
Right arrow Articles by Hannink, M.

 Previous Article  |  Next Article 

Molecular and Cellular Biology, November 2003, p. 8137-8151, Vol. 23, No. 22
0270-7306/03/$08.00+0     DOI: 10.1128/MCB.23.22.8137-8151.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Distinct Cysteine Residues in Keap1 Are Required for Keap1-Dependent Ubiquitination of Nrf2 and for Stabilization of Nrf2 by Chemopreventive Agents and Oxidative Stress

Donna D. Zhang and Mark Hannink*

Department of Biochemistry, University of Missouri—Columbia, Columbia, Missouri 65212

Received 6 June 2003/ Returned for modification 21 July 2003/ Accepted 4 August 2003

A common feature of diverse chemopreventive agents is the ability to activate expression of a genetic program that protects cells from reactive chemical species that, if left unchecked, would cause mutagenic DNA damage. The bZIP transcription factor Nrf2 has emerged as a key regulator of this cancer-preventive genetic program. Nrf2 is normally sequestered in the cytoplasm by a protein known as Keap1. Chemopreventive agents allow Nrf2 to escape from Keap1-mediated repression, although the molecular mechanism(s) responsible for activation of Nrf2 is not understood. In this report, we demonstrate that Keap1 does not passively sequester Nrf2 in the cytoplasm but actively targets Nrf2 for ubiquitination and degradation by the proteosome under basal culture conditions. We have identified two critical cysteine residues in Keap1, C273 and C288, that are required for Keap1-dependent ubiquitination of Nrf2. Both sulforaphane, a chemopreventive isothiocyanate, and oxidative stress enable Nrf2 to escape Keap1-dependent degradation, leading to stabilization of Nrf2, increased nuclear localization of Nrf2, and activation of Nrf2-dependent cancer-protective genes. We have identified a third cysteine residue in Keap1, C151, that is uniquely required for inhibition of Keap1-dependent degradation of Nrf2 by sulforaphane and oxidative stress. This cysteine residue is also required for a novel posttranslational modification to Keap1 that is induced by oxidative stress. We propose that Keap1 is a component of a novel E3 ubiquitin ligase complex that is specifically targeted for inhibition by both chemopreventive agents and oxidative stress.

* Corresponding author. Mailing address: Department of Biochemistry, M716 Medical Science Building, University of Missouri—Columbia, Columbia, MO 65212. Phone: (573) 882-7971. Fax: (573) 884-4597. E-mail: hanninkm{at}missouri.edu.

Molecular and Cellular Biology, November 2003, p. 8137-8151, Vol. 23, No. 22
0022-538X/03/$08.00+0     DOI: 10.1128/MCB.23.22.8137-8151.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:



Home Help [Feedback] [For Subscribers] [Archive] [Search] [Contents]
J. Bacteriol. J. Virol. Eukaryot. Cell
Microbiol. Mol. Biol. Rev. Clin. Vaccine Immunol. All ASM Journals

Copyright © 2003 by the American Society for Microbiology. All rights reserved.