GO:0044314 protein K27-linked ubiquitination: Immune Regulation and Disease, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0044314 (protein K27-linked ubiquitination) describes the addition of ubiquitin polymers linked through lysine 27 of ubiquitin to target proteins, a noncanonical ubiquitin code distinct from K48- or K63-linked chains.
• K27-linked ubiquitination is catalyzed by specific E3 ligases such as WWP1, TRIM21, RNF185, Nedd4, TOLLIP, and Deltex2, and is reversed by deubiquitinases including OTUD6A.
• This modification regulates diverse biological processes including immune signaling, autophagy, mitophagy, cardiac hypertrophy, chemoresistance, and Th17-mediated autoimmunity.
• Dysregulation of K27-linked ubiquitination is implicated in cancer chemoresistance, nonalcoholic fatty liver disease, sepsis-induced myocardial injury, and autoimmunity.
• Key experimental approaches to study K27-linked ubiquitination include ubiquitin linkage-specific antibodies, mass spectrometry, CRISPR knockout of E3 ligases or deubiquitinases, and functional assays in disease models.
• Understanding K27-linked ubiquitination offers opportunities for therapeutic intervention by targeting E3 ligases or deubiquitinases in cancer, cardiovascular, and metabolic diseases.
Description
Protein ubiquitination is a post-translational modification that regulates nearly every aspect of eukaryotic cell biology. While K48-linked polyubiquitination typically targets proteins for proteasomal degradation and K63-linked chains mediate signaling and trafficking, K27-linked ubiquitination has emerged as a distinct noncanonical ubiquitin code with specialized functions. This modification involves the formation of ubiquitin polymers linked through lysine 27 of the ubiquitin monomer and is added to target proteins, thereby altering their stability, localization, or interactions. K27-linked ubiquitination is now recognized as a critical regulator of immune responses, autophagy, and cellular stress adaptation. Researchers study GO:0044314 because it provides a molecular framework for understanding how cells interpret ubiquitin signals beyond the canonical degradation pathway. Dysregulation of K27-linked ubiquitination has been linked to cancer chemoresistance, cardiac hypertrophy, nonalcoholic fatty liver disease, and autoimmunity, making it a promising target for therapeutic development. The growing availability of CRISPR tools and linkage-specific reagents has accelerated the discovery of E3 ligases and deubiquitinases that write and erase this modification.
protein K27-linked ubiquitination At A Glance
| GO ID | GO:0044314 |
|---|---|
| GO term | protein K27-linked ubiquitination |
| Ontology | biological_process |
| Synonym | protein K27-linked polyubiquitination |
| Major function | Addition of K27-linked ubiquitin polymers to target proteins, regulating immune signaling, autophagy, and stress responses |
| Key enzymes | E3 ligases (WWP1, TRIM21, RNF185, Nedd4, TOLLIP, Deltex2) and deubiquitinase OTUD6A |
| Subcellular context | Cytosol, mitochondria, and autophagosomal membranes |
| Disease relevance | Cancer chemoresistance, cardiac hypertrophy, NAFLD, sepsis-induced myocardial injury, autoimmunity |
What Is GO:0044314?
GO:0044314, protein K27-linked ubiquitination, is a biological process in which a polymer of ubiquitin, formed by linkages between lysine residues at position 27 of the ubiquitin monomers, is covalently added to a target protein. This process is also known as protein K27-linked polyubiquitination. It is a noncanonical form of ubiquitination that does not primarily signal for proteasomal degradation but instead modulates protein function, interactions, and localization in diverse cellular contexts.
Why Is protein K27-linked ubiquitination Important in Cell Biology?
K27-linked ubiquitination is important because it represents a nondegradative ubiquitin signal that fine-tunes protein function in immunity, autophagy, and disease. Unlike K48-linked chains that target proteins for proteasomal degradation, K27-linked chains often alter protein-protein interactions, enzymatic activity, or subcellular localization. This modification is exploited by pathogens and is dysregulated in cancer, cardiovascular disease, and metabolic disorders. Understanding GO:0044314 therefore provides mechanistic insights into disease pathogenesis and identifies potential drug targets such as E3 ligases and deubiquitinases.
• Regulates innate immune signaling and antiviral responses by targeting CGAS and other immune sensors.
• Controls autophagosome-lysosome fusion through K27-linked ubiquitination of STX17.
• Modulates mitochondrial homeostasis via mitophagy of TUFM during viral infection.
• Drives cardiac hypertrophy by stabilizing DVL2 through WWP1-mediated K27-linked ubiquitination.
• Promotes cancer chemoresistance by orchestrating AKT K27-linked atypical ubiquitination.
• Potentiates Th17-mediated autoimmunity via Nedd4-mediated K27-linked RORγt ubiquitination.
• Protects against sepsis-induced myocardial injury by degrading TfR1 through Deltex2-mediated K27-linked ubiquitination.
• Serves as a potential therapeutic target in oncology, cardiology, and immunology.
• Provides a paradigm for noncanonical ubiquitin signaling beyond K48 and K63 linkages.
• Enables discovery of linkage-specific tools and CRISPR models for functional studies.
What Happens During protein K27-linked ubiquitination?
Initiation by E3 ubiquitin ligases
In simple terms: A specific enzyme attaches the first ubiquitin to a target protein.
K27-linked ubiquitination begins when an E3 ubiquitin ligase recognizes a substrate and catalyzes the transfer of ubiquitin from an E2 conjugating enzyme to a lysine residue on the target protein. Several E3 ligases have been shown to specifically build K27-linked chains, including WWP1, TRIM21, RNF185, Nedd4, TOLLIP, and Deltex2. For example, WWP1 mediates K27-linked ubiquitination of DVL2 in cardiac hypertrophy, while TRIM21 and OTUD6A orchestrate AKT K27-linked atypical ubiquitination in cancer chemoresistance.
Chain elongation and linkage specificity
In simple terms: More ubiquitin molecules are added in a chain that is linked through a specific position on ubiquitin.
After the initial ubiquitin attachment, the chain is extended by the addition of ubiquitin monomers through lysine 27 of the preceding ubiquitin. This linkage specificity is determined by the E3 ligase and the E2 enzyme. K27-linked chains are structurally distinct and can form both linear and branched architectures. The resulting polymers serve as signaling platforms that recruit effector proteins containing ubiquitin-binding domains.
Substrate recognition and functional outcomes
In simple terms: The tagged protein changes its behavior, such as moving to a new location or interacting with different partners.
K27-linked ubiquitination can alter substrate stability, enzymatic activity, or interactions. For instance, K27-linked ubiquitination of TUFM by RNF185 promotes mitophagy during Senecavirus A infection. Similarly, K27-linked ubiquitination of STX17 by CHIP facilitates autophagosome-lysosome fusion. In immune cells, K27-linked ubiquitination of RORγt by Nedd4 potentiates Th17-mediated autoimmunity.
Reversal by deubiquitinases
In simple terms: Enzymes can remove the ubiquitin chain to reverse the signal.
Deubiquitinases (DUBs) counteract K27-linked ubiquitination by cleaving the chains. OTUD6A has been shown to remove K27-linked ubiquitin from AKT, thereby modulating chemoresistance. The balance between E3 ligases and DUBs determines the duration and intensity of the K27-linked ubiquitin signal.
Integration with autophagy and immune pathways
In simple terms: The K27 signal helps cells recycle damaged parts and fight infections.
K27-linked ubiquitination is intimately linked to selective autophagy and innate immunity. TOLLIP-mediated K27-linked ubiquitination of CGAS triggers its degradation through selective autophagy, thereby inhibiting innate immunity. CHIP-mediated K27-linked ubiquitination of STX17 promotes autophagosome-lysosome fusion, ameliorating nonalcoholic fatty liver disease. These examples illustrate how K27-linked chains serve as molecular tags for autophagic cargo recognition and immune regulation.
Key Genes Involved in GO:0044314 protein K27-linked ubiquitination
The following genes encode E3 ligases, deubiquitinases, and substrates that are directly implicated in K27-linked ubiquitination according to published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| WWP1 | E3 ligase that catalyzes K27-linked ubiquitination of DVL2 | Cardiac hypertrophy; target for heart failure therapy |
| TRIM21 | E3 ligase that promotes K27-linked ubiquitination of AKT | Cancer chemoresistance; potential biomarker |
| OTUD6A | Deubiquitinase that removes K27-linked ubiquitin from AKT | Chemoresistance; DUB target |
| RNF185 | E3 ligase that catalyzes K27-linked ubiquitination of TUFM | Mitophagy during viral infection |
| TUFM | Mitochondrial translation elongation factor; substrate of RNF185 | Mitophagy; host-pathogen interaction |
| CHIP | E3 ligase that promotes K27-linked ubiquitination of STX17 | Nonalcoholic fatty liver disease; autophagy |
| STX17 | Autophagosomal SNARE; substrate of CHIP | Autophagosome-lysosome fusion |
| Nedd4 | E3 ligase that catalyzes K27-linked ubiquitination of RORγt | Th17-mediated autoimmunity |
| RORγt | Transcription factor; substrate of Nedd4 | Th17 differentiation; autoimmunity |
| TOLLIP | E3 ligase that mediates K27-linked ubiquitination of CGAS | Innate immunity; viral evasion |
| CGAS | Cytosolic DNA sensor; substrate of TOLLIP | Antiviral immunity; autophagy |
| Deltex2 | E3 ligase that promotes K27-linked ubiquitination of TfR1 | Sepsis-induced myocardial injury |
| TfR1 | Transferrin receptor; substrate of Deltex2 | Iron metabolism; cardiac injury |
| DVL2 | Dishevelled segment polarity protein 2; substrate of WWP1 | Wnt signaling; cardiac hypertrophy |
| AKT | Serine/threonine kinase; substrate of TRIM21 and OTUD6A | Cancer chemoresistance; survival signaling |
| UL21 | Herpesvirus tegument protein; modulates K27-linked ubiquitination | Viral immune evasion |
| Senecavirus A 2C | Viral protein that interacts with K27-ubiquitinated TUFM | Viral replication; mitophagy |
How Is protein K27-linked ubiquitination Regulated?
K27-linked ubiquitination is regulated at multiple levels. The opposing activities of E3 ligases and deubiquitinases determine the steady-state levels of K27-linked chains on substrates. For example, TRIM21 and OTUD6A reciprocally regulate AKT K27-linked ubiquitination to modulate chemoresistance. Substrate availability and post-translational modifications of the E3 ligases themselves can also influence the process. In immune cells, Nedd4-mediated K27-linked ubiquitination of RORγt is potentiated by inflammatory signals, linking this modification to Th17 differentiation. Additionally, viral proteins such as UL21 can hijack the host ubiquitination machinery to degrade immune sensors, highlighting pathogen-driven regulation.
protein K27-linked ubiquitination and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| TRIM21 / OTUD6A | Cancer chemoresistance | Cancer cell lines with CRISPR knockout or overexpression of TRIM21 and OTUD6A |
| WWP1 | Cardiac hypertrophy | Mouse models of cardiac hypertrophy with WWP1 knockout or pharmacological inhibition |
| CHIP | Nonalcoholic fatty liver disease | High-fat diet mouse models with CHIP knockout or overexpression |
| Nedd4 / RORγt | Th17-mediated autoimmunity | Experimental autoimmune encephalomyelitis (EAE) models with Nedd4 or RORγt knockout |
| Deltex2 | Sepsis-induced myocardial injury | Sepsis mouse models with Deltex2 knockout or overexpression |
Cancer chemoresistance
K27-linked ubiquitination of AKT by TRIM21 promotes cancer chemoresistance, while the deubiquitinase OTUD6A removes these chains and sensitizes cells to chemotherapy. This dynamic regulation suggests that targeting the TRIM21-OTUD6A axis could overcome drug resistance in tumors.
Cardiac hypertrophy and heart failure
WWP1-mediated K27-linked ubiquitination of DVL2 stabilizes DVL2 and drives cardiac hypertrophy. Targeting WWP1 to prevent this modification has been proposed as a therapeutic strategy for heart failure. In sepsis-induced myocardial injury, Deltex2-mediated K27-linked ubiquitination of TfR1 is protective by promoting TfR1 degradation.
Nonalcoholic fatty liver disease (NAFLD)
CHIP promotes K27-linked ubiquitination of STX17, facilitating autophagosome-lysosome fusion and ameliorating NAFLD. This suggests that enhancing CHIP activity or K27-linked ubiquitination of STX17 could be beneficial in fatty liver disease.
Autoimmunity and viral evasion
Nedd4-mediated K27-linked ubiquitination of RORγt potentiates Th17-mediated autoimmunity, implicating this modification in autoimmune diseases. Conversely, herpesvirus UL21 triggers TOLLIP-mediated K27-linked ubiquitination and degradation of CGAS, inhibiting innate immunity and promoting viral evasion.
From protein K27-linked ubiquitination-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does knockout of an E3 ligase reduce K27-linked ubiquitination of a substrate? | CRISPR knockout cell lines or mouse models |
| Does a specific point mutation in ubiquitin (K27R) abolish chain formation? | Point-mutant ubiquitin knock-in cells |
| Can a tagged ubiquitin knock-in track K27-linked chains in vivo? | Knock-in of epitope-tagged ubiquitin |
| Does overexpression of a deubiquitinase reverse K27-linked ubiquitination? | Overexpression cell lines or transgenic mice |
| What is the functional impact of K27-linked ubiquitination on autophagy? | Autophagy flux assays in knockout or overexpression models |
| Can CRISPR library screening identify novel regulators of K27-linked ubiquitination? | Genome-wide CRISPR knockout or activation screens |
How to Study the protein K27-linked ubiquitination Process
| Method | What It Measures | Typical Application |
|---|---|---|
| K27-linkage-specific immunoprecipitation | Presence of K27-linked ubiquitin chains on a substrate | Validation of E3 ligase activity |
| Mass spectrometry | Ubiquitination sites and chain linkage types | Global profiling of ubiquitin chains |
| CRISPR knockout | Loss-of-function of E3 ligases or DUBs | Functional studies in cell lines and mice |
| Point mutation (K27R ubiquitin) | Inability to form K27-linked chains | Mechanistic studies of linkage specificity |
| Overexpression | Gain-of-function of E3 ligases or DUBs | Rescue experiments and disease models |
| Autophagy flux assay | Autophagosome-lysosome fusion | NAFLD and mitophagy studies |
| Immune reporter assay | Innate immune activation | Viral evasion and autoimmunity |
| Proteomics | Protein interaction networks | Identification of K27-linked ubiquitination substrates |
Linkage-specific antibodies and immunoprecipitation
Antibodies that specifically recognize K27-linked ubiquitin chains can be used in immunoprecipitation and western blotting to detect and quantify K27-linked ubiquitination of target proteins. This approach is widely used to validate E3 ligase-substrate relationships.
Mass spectrometry-based ubiquitin chain analysis
Mass spectrometry can identify ubiquitination sites and determine chain linkage types, including K27. This method provides unbiased profiling of ubiquitin chain topology on substrate proteins.
CRISPR knockout and point mutation models
CRISPR-Cas9 knockout of E3 ligases or deubiquitinases, as well as point mutation of ubiquitin or substrate lysine residues, allows functional dissection of K27-linked ubiquitination in cells and animals.
Functional assays for autophagy and immune signaling
Autophagy flux assays, mitophagy reporters, and immune activation assays (e.g., interferon reporter cells) are used to measure the downstream consequences of K27-linked ubiquitination.
How CRISPR Can Be Used to Study GO:0044314 protein K27-linked ubiquitination
Knockout
CRISPR knockout of E3 ligases such as WWP1, TRIM21, RNF185, Nedd4, TOLLIP, or Deltex2 abolishes K27-linked ubiquitination of their substrates, enabling loss-of-function studies in disease models. Knockout of deubiquitinases like OTUD6A increases K27-linked chains on AKT.
Point Mutation
Point mutation of ubiquitin lysine 27 to arginine (K27R) prevents formation of K27-linked chains, providing a powerful tool to dissect linkage-specific functions. Similarly, mutation of substrate lysine residues can identify acceptor sites for K27-linked ubiquitination.
Knock-in
Knock-in of epitope-tagged ubiquitin or substrate proteins allows tracking and purification of K27-linked ubiquitinated species in vivo. This approach is valuable for proteomic and imaging studies.
Overexpression
Overexpression of E3 ligases or deubiquitinases can amplify or suppress K27-linked ubiquitination, respectively, enabling gain-of-function experiments in cell lines and transgenic animals.
How EDITGENE Supports protein K27-linked ubiquitination Research
Researchers studying protein K27-linked ubiquitination-related genes often need to determine whether a candidate gene is causally involved in the modification and its downstream phenotypes. EDITGENE provides a comprehensive suite of CRISPR-based services to accelerate this research, from knockout and point mutation to knock-in and overexpression models, as well as library screening and bioinformatics support.
Contact EDITGENE today to design your custom CRISPR model for protein K27-linked ubiquitination research.
Frequently Asked Questions About protein K27-linked ubiquitination
What is protein K27-linked ubiquitination?
Protein K27-linked ubiquitination (GO:0044314) is a biological process in which ubiquitin polymers linked through lysine 27 of ubiquitin are added to a target protein, regulating its function without necessarily causing degradation.
What genes are involved in protein K27-linked ubiquitination?
Key genes include E3 ligases WWP1, TRIM21, RNF185, Nedd4, TOLLIP, and Deltex2, the deubiquitinase OTUD6A, and substrates such as DVL2, AKT, TUFM, STX17, RORγt, CGAS, and TfR1.
How is K27-linked ubiquitination different from K48-linked ubiquitination?
K48-linked ubiquitination typically targets proteins for proteasomal degradation, whereas K27-linked ubiquitination is noncanonical and often modulates protein interactions, localization, or activity without direct degradation.
What diseases are associated with K27-linked ubiquitination?
It is implicated in cancer chemoresistance, cardiac hypertrophy, nonalcoholic fatty liver disease, sepsis-induced myocardial injury, and Th17-mediated autoimmunity.
Which enzymes remove K27-linked ubiquitin chains?
Deubiquitinases such as OTUD6A can remove K27-linked ubiquitin from substrates like AKT.
How can I study K27-linked ubiquitination in the lab?
Common methods include K27-linkage-specific antibodies, mass spectrometry, CRISPR knockout of E3 ligases or DUBs, point mutation of ubiquitin K27, and functional autophagy or immune assays.
What is the role of K27-linked ubiquitination in autophagy?
It tags proteins like STX17 and TUFM to promote autophagosome-lysosome fusion and mitophagy, respectively.
Can K27-linked ubiquitination be targeted therapeutically?
Yes, targeting E3 ligases such as WWP1 or TRIM21, or deubiquitinases like OTUD6A, is being explored for cancer, cardiac, and autoimmune diseases.
What model systems are used to study K27-linked ubiquitination?
Cell lines with CRISPR knockout or overexpression, point-mutant ubiquitin knock-in cells, and mouse models of disease are commonly used.
How does EDITGENE support K27-linked ubiquitination research?
EDITGENE provides CRISPR knockout, point mutation, knock-in, overexpression, library screening, and bioinformatics services to study genes involved in K27-linked ubiquitination.
Conclusion
GO:0044314 protein K27-linked ubiquitination is a noncanonical ubiquitin modification that plays critical roles in immune regulation, autophagy, and disease. The identification of specific E3 ligases and deubiquitinases has illuminated its mechanisms and therapeutic potential. Continued research using CRISPR models and linkage-specific tools will further unravel its contributions to cancer, cardiovascular, and metabolic disorders.
References
- 1. Zhou Q et al.. 2022. K27-linked noncanonic ubiquitination in immune regulation.. J Leukoc Biol 111(1):223-235 PMID: 33857334
- 2. Zhao D et al.. 2021. Targeting E3 Ubiquitin Ligase WWP1 Prevents Cardiac Hypertrophy Through Destabilizing DVL2 via Inhibition of K27-Linked Ubiquitination.. Circulation 144(9):694-711 PMID: 34139860
- 3. Jiang Q et al.. 2026. TRIM21 and OTUD6A orchestrate AKT K27-linked atypical ubiquitination to modulate cancer chemoresistance.. Nat Struct Mol Biol 33(1):84-99 PMID: 41188598
- 4. Chen M et al.. 2024. Senecavirus A induces mitophagy to promote self-replication through direct interaction of 2C protein with K27-linked ubiquitinated TUFM catalyzed by RNF185.. Autophagy 20(6):1286-1313 PMID: 38084826
- 5. Rho H et al.. 2024. CHIP ameliorates nonalcoholic fatty liver disease via promoting K63- and K27-linked STX17 ubiquitination to facilitate autophagosome-lysosome fusion.. Nat Commun 15(1):8519 PMID: 39353976
- 6. Zeng Q et al.. 2025. K27-linked RORγt ubiquitination by Nedd4 potentiates Th17-mediated autoimmunity.. J Biomed Sci 32(1):26 PMID: 39972304
- 7. Ma Z et al.. 2023. Tegument protein UL21 of alpha-herpesvirus inhibits the innate immunity by triggering CGAS degradation through TOLLIP-mediated selective autophagy.. Autophagy 19(5):1512-1532 PMID: 36343628
- 8. Liu C et al.. 2026. Deltex E3 ubiquitin ligase 2 prevents sepsis-induced myocardial injury through degrading TfR1 via promoting K27-linked ubiquitination.. Cell Death Differ 33(9):1814-1828 PMID: 41772062
