title: 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.
authors.affiliation: Department of Biology and Genetics Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: Chi K
authors.initials: CK
authors.lastname: Leung
authors.affiliation: Department of Environmental Biology, College of Bioscience and Biotechnology, Chubu University, Kasugai, Aichi, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Hasegawa
authors.affiliation: Department of Biology and Genetics Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Biology and Genetics Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Deonarine
authors.affiliation: Department of Biology and Genetics Institute, University of Florida, Gainesville, Florida, USA.
authors.forename: Lanlan
authors.initials: L
authors.lastname: Tang
authors.affiliation: Department of Environmental Biology, College of Bioscience and Biotechnology, Chubu University, Kasugai, Aichi, Japan Academy of Arts and Sciences, Chubu University, Kasugai, Aichi, Japan.
authors.forename: Johji
authors.initials: J
authors.lastname: Miwa
authors.affiliation: Department of Biology and Genetics Institute, University of Florida, Gainesville, Florida, USA kchoe@ufl.edu.
authors.forename: Keith P
authors.initials: KP
authors.lastname: Choe
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D016054:DNA, Protozoan / Q000235:genetics; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000235:genetics; D007814:Larva / Q000378:metabolism; D008136:Longevity / Q000235:genetics; D011485:Protein Binding; D017510:Protein Folding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological / Q000235:genetics; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; D016054:DNA, Protozoan; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C541018:WDR-23 protein, C elegans; C073702:skn-1 protein, C elegans