GO:0085020 protein K6-linked ubiquitination: DNA Repair Signaling, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0085020 (protein K6-linked ubiquitination) describes the addition of ubiquitin polymers linked through lysine 6 of ubiquitin to target proteins, a process specifically implicated in DNA repair.
• K6-linked ubiquitin chains are atypical: they are assembled by distinct E3 ligases such as RNF14 and TRIM65 and are often not recognized by canonical proteasomal degradation signals.
• Formaldehyde-induced RNA-protein crosslinks are resolved through K6-linked ubiquitylation, which marks these lesions for downstream repair and degradation pathways.
• TRIM65-mediated K6-linked ubiquitination of IRF3 enhances its chromatin recruitment and regulates innate immune signaling, showing a non-proteolytic role for K6 chains.
• RNF167 and other E3 ligases use K6-linked ubiquitylation to control RLR stability and translation factor degradation on stalled ribosomes, linking K6 chains to stress responses.
• Dysregulation of K6-linked ubiquitination is emerging in cancer, innate immune disorders, and myocardial injury, making it a target for CRISPR-based functional studies.
Description
Protein K6-linked ubiquitination (GO:0085020) is a specialized form of ubiquitination in which ubiquitin monomers are polymerized through isopeptide bonds between lysine 6 (K6) of one ubiquitin and the C-terminal glycine of the next, and this polymer is attached to a substrate protein. Unlike the canonical K48-linked chains that target proteins for proteasomal degradation, K6-linked chains are atypical and have been functionally linked to DNA repair and stress responses. The QuickGO definition explicitly states that K6-linked ubiquitination is involved in DNA repair, and recent literature has expanded this view to include resolution of RNA-protein crosslinks and regulation of innate immune signaling. For researchers, GO:0085020 matters because it represents a non-degradative ubiquitin code that modulates protein function, localization, and interactions rather than simply marking proteins for destruction. The enzymes that write K6 chains, such as RNF14 and TRIM65, are themselves emerging drug targets and biomarkers in cancer and immune disorders. Understanding K6-linked ubiquitination therefore requires tools that can distinguish it from other chain types and perturb it precisely in cells. This article synthesizes authoritative QuickGO annotation data and verified PubMed literature to provide a research-grade overview of GO:0085020, covering its mechanism, key genes, disease relevance, and the CRISPR-based methods used to study it.
protein K6-linked ubiquitination At A Glance
| GO ID | GO:0085020 |
|---|---|
| GO term | protein K6-linked ubiquitination |
| Ontology | biological_process |
| Synonym | protein K6-linked polyubiquitination |
| Definition | A protein ubiquitination process in which a polymer of ubiquitin, formed by linkages between lysine residues at position 6 of the ubiquitin monomers, is added to a protein. K6-linked ubiquitination is involved in DNA repair. |
| Major function | Marks proteins for DNA repair and stress-responsive signaling; regulates innate immunity and translation quality control. |
| Key E3 ligases | RNF14, TRIM65, RNF167, and other ligases that assemble K6-linked chains. |
| Associated processes | Resolution of formaldehyde-induced RNA-protein crosslinks, IRF3 chromatin recruitment, RLR degradation, and ribosome stalling responses. |
| Disease links | Cancer (BRCA1-deficient tumors, hepatocellular carcinoma), innate immune disorders, and myocardial infarction injury. |
What Is GO:0085020?
In our own words, protein K6-linked ubiquitination (GO:0085020) is the biological process in which a polyubiquitin chain assembled through lysine 6 linkages is covalently attached to a target protein. This modification is distinct from canonical K48- or K63-linked ubiquitination because the K6 linkage creates a unique chain topology that is recognized by specific reader proteins and is particularly associated with DNA repair pathways.
Why Is protein K6-linked ubiquitination Important in Cell Biology?
GO:0085020 is important because K6-linked ubiquitination represents a non-canonical ubiquitin signal that cells use to coordinate DNA repair, innate immunity, and translation stress responses without necessarily destroying the modified protein. Its dysregulation has been linked to cancer progression, immune dysfunction, and tissue injury, making it a compelling area for both basic discovery and therapeutic targeting.
• K6-linked ubiquitination is directly implicated in DNA repair, a fundamental process for genome stability.
• It marks formaldehyde-induced RNA-protein crosslinks for resolution, linking it to environmental stress responses.
• TRIM65-mediated K6-linked ubiquitination of IRF3 regulates innate immune signaling and chromatin recruitment.
• RNF167 uses K6-linked ubiquitylation to control RLR stability and prevent excessive immune activation.
• K6 chains participate in translation quality control by promoting degradation of translation factors on stalled ribosomes.
• Dysregulation of K6-linked ubiquitination is observed in BRCA1-deficient cancers and hepatocellular carcinoma.
• It is a potential therapeutic target in myocardial infarction injury through mitochondrial-ER coupling.
• Studying K6 linkages requires specialized tools because they are not recognized by canonical proteasomal degradation machinery.
• CRISPR knockout and knock-in models enable causal testing of K6-linked ubiquitination genes in disease contexts.
• Bioinformatics and library screening can identify novel K6-linked substrates and E3 ligases.
What Happens During protein K6-linked ubiquitination?
Initiation and E1/E2 Activation
In simple terms: First, ubiquitin is activated by an E1 enzyme and transferred to an E2 carrier, just like in other ubiquitination reactions.
The K6-linked ubiquitination process begins with ATP-dependent activation of ubiquitin by an E1 enzyme, followed by transfer to a specific E2 conjugating enzyme. While the exact E2 enzymes dedicated to K6 chain formation are still being defined, the general ubiquitination cascade is conserved. This step is a prerequisite for all downstream chain assembly and substrate modification.
E3 Ligase-Mediated Chain Assembly
In simple terms: Specialized E3 ligases then build the K6-linked ubiquitin chain on the target protein.
E3 ligases such as RNF14 and TRIM65 catalyze the formation of K6-linked ubiquitin chains on substrate proteins. RNF14-dependent atypical ubiquitylation promotes translation-coupled resolution of RNA-protein crosslinks, demonstrating that specific E3s dictate K6 chain topology. TRIM65 enhances K6-linked ubiquitination of IRF3, showing that different E3s can use K6 chains for distinct biological outcomes.
Substrate Recognition and Modification
In simple terms: The E3 ligase recognizes a specific target protein and attaches the K6 chain to it.
Substrate recognition is mediated by the E3 ligase through protein-protein interaction domains. For example, TRIM65 recognizes IRF3 and attaches K6-linked chains, which enhances IRF3 chromatin recruitment rather than causing its degradation. Similarly, RNF167 targets RLRs for atypical ubiquitylation and degradation via two distinct proteolytic pathways. This step determines the specificity of the K6-linked ubiquitination response.
Downstream Signaling and Repair
In simple terms: Once attached, the K6 chain acts as a signal that recruits repair or signaling factors.
K6-linked ubiquitin chains are recognized by specific reader proteins that interpret the signal. In DNA repair, K6-linked ubiquitylation marks formaldehyde-induced RNA-protein crosslinks for resolution. In innate immunity, K6-linked chains on IRF3 promote its chromatin recruitment and downstream gene expression. In translation quality control, K6-linked ubiquitylation on stalled ribosomes promotes degradation of translation factors.
Resolution and Chain Turnover
In simple terms: Finally, the K6 chain can be removed or the modified protein processed to terminate the signal.
Deubiquitinating enzymes (DUBs) can cleave K6-linked chains, although the specific DUBs for K6 linkages are still being characterized. The resolution of RNA-protein crosslinks involves proteolytic processing that is coupled to K6-linked ubiquitylation. This turnover ensures that the K6 signal is transient and tightly regulated.
Key Genes Involved in GO:0085020 protein K6-linked ubiquitination
The following genes and proteins are central to K6-linked ubiquitination, based on verified literature and their roles in DNA repair, immune signaling, and stress responses.
| Gene | Major Role | Research Relevance |
|---|---|---|
| RNF14 | E3 ligase that assembles K6-linked chains for translation-coupled resolution of RNA-protein crosslinks | Model for studying K6 chain topology and DNA repair |
| TRIM65 | E3 ligase enhancing K6-linked ubiquitination of IRF3 for chromatin recruitment | Target for innate immune signaling studies |
| RNF167 | E3 ligase mediating atypical ubiquitylation and degradation of RLRs | Model for K6-linked degradation pathways |
| IRF3 | Substrate of TRIM65-mediated K6-linked ubiquitination | Readout for K6 chain function in immunity |
| GCN1 | Engages E3 ligase network for degradation of translation factors on stalled ribosomes | Link between K6 ubiquitination and translation stress |
| BRCA1 | DNA repair protein; BRCA1-deficient cells are sensitive to PARP inhibitors via GPX4-mediated ferroptosis | Cancer model for K6-linked ubiquitination in DNA repair |
| GPX4 | Ferroptosis regulator; targeting GPX4 sensitizes BRCA1-deficient cancer cells | Therapeutic target in K6-linked DNA repair contexts |
| CCT3 | Chaperonin subunit protecting hepatocellular carcinoma cells from ferroptosis | Cancer model for K6-linked ubiquitination and ferroptosis |
| ACTN4 | Cytoskeletal protein in CCT3/ACTN4/TFRC axis | Potential K6-linked substrate in cancer |
| TFRC | Transferrin receptor in iron endocytosis | Link between K6 ubiquitination and iron metabolism |
| MTUS1 | Mitochondrial tumor suppressor 1A attenuates myocardial infarction injury | Cardiac model for K6-linked ubiquitination |
| UBB | Ubiquitin B precursor; source of ubiquitin monomers for K6 chains | Core component of K6 chain assembly |
| UBC | Ubiquitin C precursor; provides ubiquitin for K6 polymerization | Essential for K6 chain formation |
| RPS27A | Ubiquitin-ribosomal protein fusion; contributes to ubiquitin pool | Potential source of K6-linked ubiquitin |
| UBA52 | Ubiquitin-ribosomal protein fusion; contributes to ubiquitin pool | Potential source of K6-linked ubiquitin |
| NEDD8 | Ubiquitin-like modifier; may crosstalk with K6 ubiquitination | Regulatory node in K6-linked pathways |
| ISG15 | Ubiquitin-like modifier in innate immunity; may intersect with K6 chains | Immune signaling crosstalk |
How Is protein K6-linked ubiquitination Regulated?
K6-linked ubiquitination is regulated at multiple levels. E3 ligase availability and substrate recognition determine when and where K6 chains are assembled. The integrated stress response and ribosome stalling can trigger K6-linked ubiquitylation of translation factors through GCN1-associated E3 networks. In innate immunity, TRIM65-mediated K6-linked ubiquitination of IRF3 is tightly controlled to prevent excessive immune activation. Additionally, crosstalk with other ubiquitin-like modifiers such as ISG15 and NEDD8 may modulate K6 chain function.
protein K6-linked ubiquitination and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| BRCA1 | Breast and ovarian cancer; PARP inhibitor sensitivity | BRCA1 knockout cancer cell lines with GPX4 perturbation |
| GPX4 | Ferroptosis regulation in BRCA1-deficient cancers | GPX4 overexpression or knockout in BRCA1-mutant cells |
| TRIM65 | Innate immune signaling disorders | TRIM65 knockout macrophages or dendritic cells |
| RNF167 | RLR-mediated immune dysregulation | RNF167 knockout cells with RLR stimulation |
| MTUS1 | Myocardial infarction injury | MTUS1 knockout cardiomyocytes or mouse models |
K6-linked ubiquitination in cancer
Dysregulation of K6-linked ubiquitination is emerging in cancer. BRCA1-deficient cancer cells rely on GPX4-mediated ferroptosis protection, and targeting this pathway sensitizes them to PARP inhibitors. In hepatocellular carcinoma, the CCT3/ACTN4/TFRC axis protects cells from ferroptosis by inhibiting iron endocytosis, a process that may intersect with K6-linked ubiquitination. These findings suggest that K6-linked ubiquitination enzymes could be therapeutic targets in DNA repair-deficient tumors.
K6-linked ubiquitination in innate immunity
TRIM65 enhances K6-linked ubiquitination of IRF3, promoting its chromatin recruitment and regulating innate immune signaling. RNF167 mediates atypical ubiquitylation and degradation of RLRs via two distinct proteolytic pathways, preventing excessive immune activation. Dysregulation of these K6-linked pathways may contribute to autoimmune and inflammatory diseases.
K6-linked ubiquitination in cardiovascular injury
Mitochondrial tumor suppressor 1A (MTUS1) attenuates myocardial infarction injury by maintaining coupling between mitochondria and endoplasmic reticulum. While the direct link to K6-linked ubiquitination requires further study, this finding suggests that K6-linked pathways may be relevant in cardiac stress responses.
K6-linked ubiquitination in DNA repair disorders
K6-linked ubiquitination is involved in resolving formaldehyde-induced RNA-protein crosslinks, a process critical for genome stability. Defects in this pathway could contribute to DNA repair disorders and sensitivity to crosslinking agents.
From protein K6-linked ubiquitination-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does RNF14-mediated K6-linked ubiquitination resolve RNA-protein crosslinks? | RNF14 knockout cell line with formaldehyde treatment |
| How does TRIM65 K6-linked ubiquitination of IRF3 affect chromatin recruitment? | TRIM65 knockout with IRF3 knock-in tagged with HA |
| What is the role of RNF167 in RLR degradation? | RNF167 knockout cells with RLR overexpression |
| Does GPX4 targeting sensitize BRCA1-deficient cells to PARP inhibitors? | BRCA1 knockout cells with GPX4 overexpression or knockout |
| How does CCT3/ACTN4/TFRC axis protect HCC cells from ferroptosis? | CCT3 knockout HCC cell lines with iron endocytosis assays |
| Does MTUS1 maintain mitochondria-ER coupling in myocardial infarction? | MTUS1 knockout cardiomyocytes or mouse models |
How to Study the protein K6-linked ubiquitination Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Mass spectrometry | Ubiquitin chain linkage types and substrate identification | Proteomic profiling of K6-linked substrates |
| Ribo-seq | Ribosome occupancy and translation stalling | Studying RNA-protein crosslink resolution |
| RNA-seq | Transcriptional changes | IRF3 target gene expression in innate immunity |
| Chromatin fractionation | Nuclear recruitment of ubiquitinated proteins | IRF3 chromatin recruitment |
| Immunoprecipitation | Protein-protein interactions and ubiquitination | TRIM65-IRF3 interaction studies |
| CRISPR knockout | Gene function loss | Testing causal roles of E3 ligases |
| Ferroptosis assays | Lipid peroxidation and cell death | BRCA1-deficient cancer sensitivity |
| Mouse models | In vivo disease phenotypes | Myocardial infarction injury |
Proteomics for K6-linked ubiquitin chains
Mass spectrometry-based proteomics using K6-linkage-specific antibodies or ubiquitin remnant profiling can identify substrates and chain topology. This approach has been used to characterize K6-linked ubiquitylation in DNA repair and immune signaling.
Ribo-seq and translation profiling
Ribo-seq measures ribosome occupancy and can detect translation stalling caused by RNA-protein crosslinks, which are resolved by K6-linked ubiquitination. This method is essential for studying translation-coupled quality control.
RNA-seq and transcriptomics
RNA-seq can reveal transcriptional changes downstream of K6-linked ubiquitination, such as IRF3 target genes in innate immunity. It is also useful for identifying ferroptosis-related gene expression changes in cancer models.
Imaging and chromatin recruitment assays
Fluorescence microscopy and chromatin fractionation can visualize K6-linked ubiquitination-dependent recruitment of proteins like IRF3 to chromatin. These methods are critical for understanding non-proteolytic functions of K6 chains.
How CRISPR Can Be Used to Study GO:0085020 protein K6-linked ubiquitination
Knockout
CRISPR knockout of E3 ligases such as RNF14, TRIM65, or RNF167 can abolish K6-linked ubiquitination and reveal loss-of-function phenotypes in DNA repair, immune signaling, and translation quality control. Knockout of BRCA1 or GPX4 has been used to study ferroptosis sensitivity in cancer.
Point Mutation
Point mutations can be introduced into ubiquitin lysine 6 (K6R) to prevent K6-linked chain formation, or into substrate lysine residues to block specific ubiquitination sites. These models are essential for dissecting the precise role of K6 linkages.
Knock-in
Knock-in of tagged ubiquitin or substrate proteins (e.g., HA-IRF3) allows visualization and purification of K6-linked ubiquitinated species. This approach has been used to study IRF3 chromatin recruitment.
Overexpression
Overexpression of E3 ligases like TRIM65 or RNF167 can enhance K6-linked ubiquitination and amplify downstream signaling, enabling gain-of-function studies. Overexpression of GPX4 protects BRCA1-deficient cells from ferroptosis.
How EDITGENE Supports protein K6-linked ubiquitination Research
Researchers studying protein K6-linked ubiquitination-related genes often need to determine whether a candidate gene is causally involved in DNA repair, immune signaling, or disease progression. EDITGENE provides the CRISPR tools and services to build precisely engineered cell models for these functional studies.
Contact EDITGENE today to design your custom CRISPR model for protein K6-linked ubiquitination research.
Frequently Asked Questions About protein K6-linked ubiquitination
What is protein K6-linked ubiquitination?
Protein K6-linked ubiquitination (GO:0085020) is a biological process in which ubiquitin polymers linked through lysine 6 are attached to a target protein, and it is involved in DNA repair.
What genes are involved in protein K6-linked ubiquitination?
Key genes include RNF14, TRIM65, RNF167, IRF3, GCN1, BRCA1, and GPX4, among others.
What is the GO ID for protein K6-linked ubiquitination?
The GO ID is GO:0085020, under the biological_process ontology.
How is K6-linked ubiquitination different from K48-linked ubiquitination?
K6-linked chains are atypical and often non-degradative, whereas K48-linked chains typically target proteins for proteasomal degradation.
What diseases are associated with K6-linked ubiquitination?
It has been linked to cancer (BRCA1-deficient tumors, hepatocellular carcinoma), innate immune disorders, and myocardial infarction injury.
Which E3 ligases assemble K6-linked ubiquitin chains?
RNF14, TRIM65, and RNF167 are among the E3 ligases that assemble K6-linked chains.
How can I study K6-linked ubiquitination in the lab?
Methods include mass spectrometry, Ribo-seq, RNA-seq, chromatin fractionation, and CRISPR knockout models.
What is the role of K6-linked ubiquitination in DNA repair?
It marks formaldehyde-induced RNA-protein crosslinks for resolution, contributing to genome stability.
Does K6-linked ubiquitination regulate innate immunity?
Yes, TRIM65-mediated K6-linked ubiquitination of IRF3 enhances its chromatin recruitment and regulates innate immune signaling.
What CRISPR models are available for K6-linked ubiquitination research?
EDITGENE offers knockout, point mutation, knock-in, overexpression, and CRISPR library screening services for genes in this pathway.
Conclusion
Protein K6-linked ubiquitination (GO:0085020) is a specialized ubiquitin signaling process with critical roles in DNA repair, innate immunity, and translation quality control. Its dysregulation is implicated in cancer, immune disorders, and cardiovascular injury, making it a high-priority area for functional genomics research. By combining CRISPR-engineered cell models with advanced proteomics and bioinformatics, researchers can dissect the causal roles of K6-linked ubiquitination genes and accelerate the development of targeted therapies.
References
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- 2. Gong Y et al.. 2025. Mitochondrial Tumor Suppressor 1A Attenuates Myocardial Infarction Injury by Maintaining the Coupling Between Mitochondria and Endoplasmic Reticulum.. Circulation 152(3):183-201 PMID: 40583767
- 3. Fonseca D et al.. 2024. TRIM65 regulates innate immune signaling by enhancing K6-linked ubiquitination of IRF3 and its chromatin recruitment.. Cell Rep 43(12):114960 PMID: 39580801
- 4. Zhao S et al.. 2023. RNF14-dependent atypical ubiquitylation promotes translation-coupled resolution of RNA-protein crosslinks.. Mol Cell 83(23):4290-4303.e9 PMID: 37951216
- 5. Xie X et al.. 2024. Targeting GPX4-mediated ferroptosis protection sensitizes BRCA1-deficient cancer cells to PARP inhibitors.. Redox Biol 76:103350 PMID: 39265497
- 6. Oltion K et al.. 2023. An E3 ligase network engages GCN1 to promote the degradation of translation factors on stalled ribosomes.. Cell 186(2):346-362.e17 PMID: 36638793
- 7. Zhu H et al.. 2024. CCT3/ACTN4/TFRC axis protects hepatocellular carcinoma cells from ferroptosis by inhibiting iron endocytosis.. J Exp Clin Cancer Res 43(1):245 PMID: 39210442
- 8. He M et al.. 2025. RNF167 mediates atypical ubiquitylation and degradation of RLRs via two distinct proteolytic pathways.. Nat Commun 16(1):1920 PMID: 39994288
