The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
Plan summary
We validated the identity of C. elegans skn-1 (UniProt P34707) and compiled recent, authoritative evidence (prioritizing 2023–2024) on its molecular function, pathways, localization, regulation, and activation by dietary phytochemicals. We synthesized mechanistic updates and quantitative findings into a structured research report with citations and URLs.
| Year | Citation (short) | URL / DOI | Evidence Focus |
|---|---|---|---|
| 2024 | Turner CD, Ramos CM, Curran SP, "Disrupting the SKN-1 homeostat" (Frontiers in Aging) | https://doi.org/10.3389/fragi.2024.1369740 | Isoforms SKN‑1A/B/C and tissue localization (ER/ASI neurons/intestine); regulation by WDR‑23–CUL4/DDB1, PMK‑1/p38, insulin/DAF‑2→AKT, mTORC2→SGK‑1; direct activation of Phase II detox genes (GSTs, gst‑4 reporter) and proteasome genes; developmental mesendoderm specification; stress‑induced nuclear translocation. (turner2024disruptingtheskn1 pages 2-3, turner2024disruptingtheskn1 pages 7-8, turner2024disruptingtheskn1 pages 8-9) |
| 2024 | Farias‑Pereira R., Camayoc P., Raskin I., "Isothiocyanate‑Rich Moringa Seed Extract Activates SKN‑1/Nrf2" (IJMS) | https://doi.org/10.3390/ijms252010917 | MIC‑1 (moringin) upregulates skn‑1 expression and induces SKN‑1 nuclear translocation; upregulation of multiple GSTs (gst‑7, gst‑31, gst‑33, gst‑37, gst‑39, gsto‑3) and antioxidant genes; gst‑4 induction is SKN‑1 dependent; purified MIC‑1 increased lifespan while whole extract had mixed effects. (fariaspereira2024isothiocyanaterichmoringaseed pages 1-2) |
| 2024 | Hirayama M., Oguro A., Tanaka M., Imaoka S., "Sulforaphane induces Nrf2 (cSKN‑1) via WDR23" (ResearchSquare preprint) | https://doi.org/10.21203/rs.3.rs-4308876/v1 | Sulforaphane activates SKN‑1 in a WDR‑23–dependent, KEAP1‑independent manner; implicates DDB1/CUL4 ubiquitin ligase axis and FOXO/DAF‑16 cross‑talk in lifespan effects; skn‑1 and gcs‑1 expression assayed. (hirayama2024lifespanextensionof pages 10-12) |
| 2023 | Cho M., Kim Y., You S., Hwang DY., Jang M., "Chlorogenic Acid ... via SKN‑1/DAF‑16" (Metabolites) | https://doi.org/10.3390/metabo13020224 | Chlorogenic acid reduces ROS and extends healthspan/lifespan via SKN‑1 and DAF‑16 dependence; effects diminished in skn‑1 and daf‑16 mutants; implicates GST/gcs targets and reporter/mutant assays for SKN‑1 requirement. (hirayama2024lifespanextensionof pages 10-12) |
Table: Compact table summarizing major 2023–2024 studies/reviews on C. elegans SKN‑1 (UniProt P34707), listing DOI/URLs and the specific mechanistic or phenotypic evidence each provides (isoforms, regulators, targets, localization, and phytochemical activation).
Research report: C. elegans skn-1 (UniProt P34707)
1) Key concepts and definitions
- Identity and family: skn-1 encodes the C. elegans ortholog of CNC/Nrf transcription factors and functions as the principal Nrf-like regulator of xenobiotic and oxidative stress defenses in the worm. It belongs to the bZIP/CNC-related family, though C. elegans SKN-1 lacks a canonical leucine zipper and appears capable of monomeric DNA binding via an extended N-terminal arm that confers specificity, consistent with its Nrf2-like role in stress-responsive transcription (review synthesis) (turner2024disruptingtheskn1 pages 2-3).
- Isoforms and localization: Three major isoforms perform distinct functions. SKN-1A is ER-associated via an N-terminal transmembrane domain and is activated during proteasome stress through ERAD-linked processing (DDI-1/PNG-1), upregulating proteasome components. SKN-1C primarily mediates oxidative/xenobiotic stress responses in the intestine. SKN-1B acts in ASI sensory neurons to mediate dietary-restriction/calcic restriction–linked longevity; neuronal activation can trigger body-wide stress programs, including gst-4 reporters in peripheral tissues (review synthesis) (turner2024disruptingtheskn1 pages 3-4, turner2024disruptingtheskn1 pages 2-3).
- DNA binding and targets: SKN-1 activates classic Phase II detoxification and antioxidant genes (e.g., glutathione S-transferases and glutathione biosynthesis genes), with gst-4 and gcs-1 widely used as canonical readouts/targets. In vivo reporter studies (gst-4p::GFP) and transcriptomics support SKN-1-dependent induction of GSTs and related detox genes (turner2024disruptingtheskn1 pages 3-4, fariaspereira2024isothiocyanaterichmoringaseed pages 1-2, hirayama2024lifespanextensionof pages 10-12). While ARE-like motifs are implicated, exact motif sequence details are not specified in the cited 2023–2024 sources.
- Developmental role: Maternal skn-1 is essential for early embryonic mesendoderm/endoderm specification, a classic developmental function that is distinct from its later stress-response roles (review synthesis) (turner2024disruptingtheskn1 pages 13-13, turner2024disruptingtheskn1 pages 14-14).
2) Recent developments and latest research (2023–2024 prioritized)
- System-level regulation (“SKN-1 homeostat”): A 2024 expert review synthesizes how proteostatic turnover, kinase signaling, metabolic and epigenetic inputs calibrate SKN-1 activity. Key updates include isoform-specific mechanisms (ER-bound SKN-1A processing in proteasome stress), nuclear translocation dynamics in intestine and neurons, and tradeoffs of chronic activation (stress resistance vs later-life health detriments and Asdf lipid phenotypes) (Frontiers in Aging, Mar 2024; https://doi.org/10.3389/fragi.2024.1369740) (turner2024disruptingtheskn1 pages 2-3, turner2024disruptingtheskn1 pages 7-8, turner2024disruptingtheskn1 pages 11-12).
- WDR-23–CUL4/DDB1 ubiquitin-ligase control: Newer summaries emphasize two WDR-23 isoforms with distinct compartmentalization (mitochondrial WDR-23A vs nuclear WDR-23B), providing spatial control over SKN-1 turnover and linking mitochondrial stress/ROS to SKN-1 regulation. wdr-23 knockdown causes SKN-1 nuclear accumulation in intestinal cells (turner2024disruptingtheskn1 pages 8-9).
- Kinase and chromatin regulators: 2024 synthesis highlights p38/PMK-1–dependent activation by ROS, negative regulation via insulin-like signaling (DAF-2→AKT) and SGK-1/mTORC2, and positive roles of CBP-1 coactivator; SUMOylation/NEDDylation influence SKN-1 nuclear abundance and activity (turner2024disruptingtheskn1 pages 11-12, turner2024disruptingtheskn1 pages 8-9, turner2024disruptingtheskn1 pages 14-15).
- Context switching and innate immunity: Recent analyses show SKN-1 can switch target programs between oxidative-stress genes (e.g., gst-4) and innate immunity genes (dod-24, endu-2, clec-66) depending on stimuli such as paraquat vs perceived pathogen/metabolic states, with implications for longevity and pathogen resistance (turner2024disruptingtheskn1 pages 7-8).
- Neuronal–intestinal coupling: 2023–2024 studies support that SKN-1 activation in ASI neurons can drive multi-tissue responses and reprogram metabolism and mitochondrial function under dietary restriction (turner2024disruptingtheskn1 pages 3-4, turner2024disruptingtheskn1 pages 14-15).
3) Current applications and real-world implementations
- Biomarker/reporters: gst-4p::GFP remains a standard in vivo reporter of SKN-1 activity; intestinal nuclear translocation of SKN-1 and induction of gst-4 are used to measure oxidative/xenobiotic pathway activation (turner2024disruptingtheskn1 pages 3-4, fariaspereira2024isothiocyanaterichmoringaseed pages 1-2).
- Nutraceutical/phytochemical discovery: C. elegans skn-1 is widely used to screen and mechanistically profile dietary compounds for Nrf2-like cytoprotective activity. Recent studies (2023–2024) evaluated isothiocyanates (MIC-1/moringin), sulforaphane, and chlorogenic acid for SKN-1 activation and healthspan/lifespan effects, including SKN-1 dependence and WDR-23 axis involvement (fariaspereira2024isothiocyanaterichmoringaseed pages 1-2, hirayama2024lifespanextensionof pages 10-12).
- Pharmacological and metabolic interventions: Biguanides (metformin/phenformin) and ether-lipid metabolism intersect with SKN-1 to remodel lipid stores (Asdf phenotype), innate immunity gene expression, and lifespan outcomes, providing a platform for studying metabolic stress defenses and therapeutic mimetics (turner2024disruptingtheskn1 pages 7-8, turner2024disruptingtheskn1 pages 14-15).
4) Expert opinions and analysis (authoritative sources)
- The 2024 Frontiers in Aging review frames SKN-1 as a tightly regulated “homeostat,” integrating stress, nutrient, and proteostatic cues through WDR-23–CUL4/DDB1–mediated turnover and kinase/chromatin control. It emphasizes the importance of controlled, transient activation; constitutive activation improves early stress resistance but can produce detrimental late-life phenotypes (lipid depletion/Asdf, reduced healthspan), underscoring the need to understand deactivation and isoform specificity (https://doi.org/10.3389/fragi.2024.1369740) (turner2024disruptingtheskn1 pages 11-12, turner2024disruptingtheskn1 pages 7-8, turner2024disruptingtheskn1 pages 14-14).
- Regulatory architecture: Relative to mammalian Keap1–Nrf2, C. elegans lacks Keap1 and uses WDR-23 as the principal adaptor, with two isoforms enabling spatial control (mitochondrial vs nuclear). This is increasingly seen as a conserved alternative pathway as WDR23 can regulate mammalian NRF2 independently of Keap1, aligning nematode and mammalian insights (turner2024disruptingtheskn1 pages 8-9, hirayama2024lifespanextensionof pages 10-12).
- Isoform-centric view: SKN-1A (ER/proteasome stress) and SKN-1B (neuronal/dietary restriction) broaden SKN-1 beyond a simple oxidative-stress factor, integrating proteostasis and neuroendocrine inputs into whole-animal stress physiology (turner2024disruptingtheskn1 pages 3-4, turner2024disruptingtheskn1 pages 2-3).
5) Relevant statistics and data from recent studies (with URLs/dates)
- Isothiocyanate-rich Moringa seed extract (MIC-1/moringin; IJMS, Oct 2024): At 0.1 mg/mL MSE (≈100 μM MIC-1), RNA-seq identified 1,555 differentially expressed genes (935 up, 620 down). Multiple GSTs and antioxidant genes were upregulated; gst-4 induction required skn-1. MSE induced SKN-1 nuclear translocation; purified MIC-1 increased lifespan, whereas the complex extract reduced survivability and delayed growth, implying other extract components have adverse effects (https://doi.org/10.3390/ijms252010917) (fariaspereira2024isothiocyanaterichmoringaseed pages 1-2).
- Sulforaphane via WDR-23 (ResearchSquare preprint, May 2024): Sulforaphane induced SKN-1 through the WDR-23–CUL4/DDB1 pathway, KEAP1-independent; skn-1 and gcs-1 were measured as markers. Lifespan extension required skn-1 and daf-16/FOXO orthologs, as SFN did not extend lifespan in skn-1 or daf-16 mutants, consistent with SKN-1/DAF-16 cross-talk (https://doi.org/10.21203/rs.3.rs-4308876/v1) (hirayama2024lifespanextensionof pages 10-12).
- Chlorogenic acid (Metabolites, Feb 2023): Reduced ROS, extended lifespan/healthspan in a skn-1– and daf-16–dependent manner; SKN-1 dependence inferred from reduced effects in skn-1 mutants and canonical antioxidant readouts. The study supports staged reliance on daf-16 vs skn-1 under different oxidative burdens (https://doi.org/10.3390/metabo13020224) (hirayama2024lifespanextensionof pages 10-12).
- Reporter/localization updates (2023–2024 reviews): Intestinal nuclear translocation upon oxidative stress (e.g., arsenite); neuronal SKN-1B activity in ASI neurons sufficient to drive multi-tissue gst-4 reporter activation; proteasome stress–dependent release/processing of SKN-1A from the ER to induce proteasome genes (https://doi.org/10.3389/fragi.2024.1369740) (turner2024disruptingtheskn1 pages 3-4, turner2024disruptingtheskn1 pages 2-3).
Functional annotation summary
- Primary molecular function: SKN-1 is a transcription factor that activates detoxification and antioxidant defense programs (Phase II GSTs and glutathione biosynthesis genes, among others), context-dependently regulating innate immunity and proteostasis/proteasome genes via its isoforms (turner2024disruptingtheskn1 pages 3-4, turner2024disruptingtheskn1 pages 7-8, fariaspereira2024isothiocyanaterichmoringaseed pages 1-2, hirayama2024lifespanextensionof pages 10-12).
- Subcellular/cellular localization: Basally, SKN-1B is active in ASI neurons; SKN-1C accumulates in intestinal nuclei upon oxidative stress; SKN-1A localizes to the ER and is mobilized during proteasome stress (turner2024disruptingtheskn1 pages 3-4, turner2024disruptingtheskn1 pages 2-3).
- Pathway integration: Upstream negative control by WDR-23–CUL4/DDB1 drives proteasomal turnover; activation via p38/PMK-1 during ROS; modulation by insulin-like signaling (DAF-2→AKT) and mTORC2→SGK-1; positive regulation by CBP-1; modification by SUMOylation/NEDDylation. SKN-1 coordinates oxidative/xenobiotic defenses, innate immunity, lipid metabolism, and proteasome/mitochondrial stress responses (turner2024disruptingtheskn1 pages 8-9, turner2024disruptingtheskn1 pages 11-12, turner2024disruptingtheskn1 pages 14-15).
- Recent activation by phytochemicals: MIC-1 (moringin) activates SKN-1, induces nuclear translocation and SKN-1–dependent gst-4 upregulation; sulforaphane acts via the WDR-23 axis and requires skn-1 and daf-16 for lifespan extension; chlorogenic acid extends lifespan/healthspan in a skn-1–dependent fashion (fariaspereira2024isothiocyanaterichmoringaseed pages 1-2, hirayama2024lifespanextensionof pages 10-12).
Notes on gene/protein identification and domains
- The skn-1 gene in C. elegans encodes a CNC/Nrf-like bZIP transcription factor with unique structural features relative to mammalian Nrf2 (reduced reliance on a leucine zipper; monomeric DNA binding capacity). The reviewed literature explicitly analyzes SKN-1 isoforms (A/B/C) and their cellular localizations and roles, in line with UniProt P34707 annotations for a bZIP family SKN-1 protein (turner2024disruptingtheskn1 pages 2-3, turner2024disruptingtheskn1 pages 3-4).
References (URLs and dates)
- Turner CD, Ramos CM, Curran SP. Disrupting the SKN-1 homeostat: mechanistic insights and phenotypic outcomes. Frontiers in Aging. Mar 2024. https://doi.org/10.3389/fragi.2024.1369740 (turner2024disruptingtheskn1 pages 2-3, turner2024disruptingtheskn1 pages 7-8, turner2024disruptingtheskn1 pages 11-12, turner2024disruptingtheskn1 pages 3-4).
- Farias-Pereira R, Camayoc P, Raskin I. Isothiocyanate-Rich Moringa Seed Extract Activates SKN-1/Nrf2 Pathway in Caenorhabditis elegans. Int J Mol Sci. Oct 2024;25:10917. https://doi.org/10.3390/ijms252010917 (fariaspereira2024isothiocyanaterichmoringaseed pages 1-2).
- Hirayama M, Oguro A, Tanaka M, Imaoka S. Lifespan extension of Caenorhabditis elegans by sulforaphane: Sulforaphane induces Nrf2 (cSKN-1) via WDR23, but not keap1. ResearchSquare preprint. May 2024. https://doi.org/10.21203/rs.3.rs-4308876/v1 (hirayama2024lifespanextensionof pages 10-12).
- Cho M, Kim Y, You S, Hwang DY, Jang M. Chlorogenic Acid of Cirsium japonicum Resists Oxidative Stress Caused by Aging and Prolongs Healthspan via SKN-1/Nrf2 and DAF-16/FOXO in Caenorhabditis elegans. Metabolites. Feb 2023;13(2):224. https://doi.org/10.3390/metabo13020224 (hirayama2024lifespanextensionof pages 10-12).
Limitations and open questions
- Precise SKN-1 DNA-binding consensus sequence and detailed isoform-specific interactomes were not explicitly available in the 2023–2024 sources cited here; earlier structural work defines noncanonical DNA contacts and monomeric binding, and ongoing studies are refining isoform-specific regulatory networks (turner2024disruptingtheskn1 pages 2-3).
- Quantitative lifespan effect sizes for individual phytochemicals (e.g., percent extension for MIC-1, sulforaphane, chlorogenic acid) were not explicitly reported in the cited excerpts; where measured, the dependence on skn-1 and daf-16 and the directionality of effects are supported (fariaspereira2024isothiocyanaterichmoringaseed pages 1-2, hirayama2024lifespanextensionof pages 10-12).
Conclusion
C. elegans SKN-1 (UniProt P34707) is a CNC/Nrf-like bZIP transcription factor with three isoforms that coordinate antioxidant/xenobiotic defenses, innate immunity, proteostasis and metabolic remodeling. Its activity is tuned by WDR-23–CUL4/DDB1–mediated turnover, kinase pathways (p38/PMK-1, AKT, SGK-1), coactivators (CBP-1), and ubiquitin-like modifiers. Recent work (2023–2024) underscores isoform-specific regulation (ER-associated SKN-1A; neuronal SKN-1B; intestinal SKN-1C), the consequences of chronic activation, and activation by dietary isothiocyanates, sulforaphane (via WDR-23), and chlorogenic acid, with skn-1 dependence verified by reporters and mutant analyses (turner2024disruptingtheskn1 pages 3-4, turner2024disruptingtheskn1 pages 8-9, turner2024disruptingtheskn1 pages 11-12, fariaspereira2024isothiocyanaterichmoringaseed pages 1-2, hirayama2024lifespanextensionof pages 10-12).
References
(turner2024disruptingtheskn1 pages 2-3): Chris D. Turner, Carmen M. Ramos, and Sean P. Curran. Disrupting the skn-1 homeostat: mechanistic insights and phenotypic outcomes. Frontiers in Aging, Mar 2024. URL: https://doi.org/10.3389/fragi.2024.1369740, doi:10.3389/fragi.2024.1369740. This article has 15 citations and is from a poor quality or predatory journal.
(turner2024disruptingtheskn1 pages 7-8): Chris D. Turner, Carmen M. Ramos, and Sean P. Curran. Disrupting the skn-1 homeostat: mechanistic insights and phenotypic outcomes. Frontiers in Aging, Mar 2024. URL: https://doi.org/10.3389/fragi.2024.1369740, doi:10.3389/fragi.2024.1369740. This article has 15 citations and is from a poor quality or predatory journal.
(turner2024disruptingtheskn1 pages 8-9): Chris D. Turner, Carmen M. Ramos, and Sean P. Curran. Disrupting the skn-1 homeostat: mechanistic insights and phenotypic outcomes. Frontiers in Aging, Mar 2024. URL: https://doi.org/10.3389/fragi.2024.1369740, doi:10.3389/fragi.2024.1369740. This article has 15 citations and is from a poor quality or predatory journal.
(fariaspereira2024isothiocyanaterichmoringaseed pages 1-2): Renalison Farias-Pereira, Pierre Camayoc, and Ilya Raskin. Isothiocyanate-rich moringa seed extract activates skn-1/nrf2 pathway in caenorhabditis elegans. International Journal of Molecular Sciences, 25:10917, Oct 2024. URL: https://doi.org/10.3390/ijms252010917, doi:10.3390/ijms252010917. This article has 2 citations and is from a poor quality or predatory journal.
(hirayama2024lifespanextensionof pages 10-12): Moe Hirayama, Ami Oguro, Masako Tanaka, and Susumu Imaoka. Lifespan extension of caenorhabditis elegans by sulforafane: sulforafane induces nrf2 (cskn-1) via wdr23, but not keap1. May 2024. URL: https://doi.org/10.21203/rs.3.rs-4308876/v1, doi:10.21203/rs.3.rs-4308876/v1.
(turner2024disruptingtheskn1 pages 3-4): Chris D. Turner, Carmen M. Ramos, and Sean P. Curran. Disrupting the skn-1 homeostat: mechanistic insights and phenotypic outcomes. Frontiers in Aging, Mar 2024. URL: https://doi.org/10.3389/fragi.2024.1369740, doi:10.3389/fragi.2024.1369740. This article has 15 citations and is from a poor quality or predatory journal.
(turner2024disruptingtheskn1 pages 13-13): Chris D. Turner, Carmen M. Ramos, and Sean P. Curran. Disrupting the skn-1 homeostat: mechanistic insights and phenotypic outcomes. Frontiers in Aging, Mar 2024. URL: https://doi.org/10.3389/fragi.2024.1369740, doi:10.3389/fragi.2024.1369740. This article has 15 citations and is from a poor quality or predatory journal.
(turner2024disruptingtheskn1 pages 14-14): Chris D. Turner, Carmen M. Ramos, and Sean P. Curran. Disrupting the skn-1 homeostat: mechanistic insights and phenotypic outcomes. Frontiers in Aging, Mar 2024. URL: https://doi.org/10.3389/fragi.2024.1369740, doi:10.3389/fragi.2024.1369740. This article has 15 citations and is from a poor quality or predatory journal.
(turner2024disruptingtheskn1 pages 11-12): Chris D. Turner, Carmen M. Ramos, and Sean P. Curran. Disrupting the skn-1 homeostat: mechanistic insights and phenotypic outcomes. Frontiers in Aging, Mar 2024. URL: https://doi.org/10.3389/fragi.2024.1369740, doi:10.3389/fragi.2024.1369740. This article has 15 citations and is from a poor quality or predatory journal.
(turner2024disruptingtheskn1 pages 14-15): Chris D. Turner, Carmen M. Ramos, and Sean P. Curran. Disrupting the skn-1 homeostat: mechanistic insights and phenotypic outcomes. Frontiers in Aging, Mar 2024. URL: https://doi.org/10.3389/fragi.2024.1369740, doi:10.3389/fragi.2024.1369740. This article has 15 citations and is from a poor quality or predatory journal.