Direct Interaction between the WD40 Repeat Protein WDR-23 and SKN-1/Nrf Inhibits Binding to Target DNA

Abstract

SKN-1/Nrf transcription factors activate cytoprotective genes in response to reactive small molecules and strongly influence stress resistance, longevity, and development. The molecular mechanisms of SKN-1/Nrf regulation are poorly defined. We previously identified the WD40 repeat protein WDR-23 as a repressor of Caenorhabditis elegans SKN-1 that functions with a ubiquitin ligase to presumably target the factor for degradation. However, SKN-1 activity and nuclear accumulation are not always correlated, suggesting that there could be additional regulatory mechanisms. Here, we integrate forward genetics and biochemistry to gain insights into how WDR-23 interacts with and regulates SKN-1. We provide evidence that WDR-23 preferentially regulates one of three SKN-1 variants through a direct interaction that is required for normal stress resistance and development. Homology modeling predicts that WDR-23 folds into a β-propeller, and we identify the top of this structure and four motifs at the termini of SKN-1c as essential for the interaction. Two of these SKN-1 motifs are highly conserved in human Nrf1 and Nrf2 and two directly interact with target DNA. Lastly, we demonstrate that WDR-23 can block the ability of SKN-1c to interact with DNA sequences of target promoters identifying a new mechanism of regulation that is independent of the ubiquitin proteasome system, which can become occupied with damaged proteins during stress.

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Retraction for Leung et al., Direct Interaction between the WD40 Repeat Protein WDR-23 and SKN-1/Nrf Inhibits Binding to Target DNA

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00114-14.

ACKNOWLEDGMENTS

Some C. elegans strains were provided by the Caenorhabditis Genetics Center (University of Minnesota, Minneapolis, MN).

All authors participated in proposing, designing, and performing the experiments and in analysis and interpretation of data. C.K.L. and K.P.C. wrote the manuscript, and all authors approved the final version for publication.

This study was funded by NSF grant IOS-1120130 to K.P.C. and a Grant-in-Aid for Scientific Research of MEXT to J.M.