GO:0080008 Cul4-RING E3 ubiquitin ligase complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0080008 defines the Cul4-RING E3 ubiquitin ligase complex (CRL4), a modular ubiquitin ligase whose catalytic core comprises a CUL4 family cullin and a RING-domain protein, with substrate specificity provided by adaptor proteins.
• CRL4 complexes are assembled from CUL4, RBX1/ROC1, DDB1, and a large family of DCAF substrate receptors, enabling recognition of diverse substrates.
• CRL4 ligases regulate cell-cycle progression, DNA replication, DNA damage responses, autophagy, and metabolic gene expression.
• Dysregulation of CRL4 components is implicated in cancer, including lung cancer metastasis, endometrial cancer, and cell-cycle control.
• CRISPR-based knockout, point-mutation, knock-in, and overexpression models are essential for dissecting CRL4 subunit function and substrate specificity.
• Understanding CRL4 biology offers opportunities for targeted therapies, particularly in cancers driven by aberrant CRL4 activity.
Description
The Cul4-RING E3 ubiquitin ligase complex (CRL4) is a multi-subunit enzyme that catalyzes the transfer of ubiquitin to specific substrate proteins, marking them for proteasomal degradation or altering their function. It belongs to the cullin-RING ligase (CRL) superfamily, which represents one of the largest classes of E3 ubiquitin ligases in eukaryotes. The CRL4 complex is defined by a catalytic core consisting of a CUL4 family cullin and a RING-domain protein, typically RBX1, while substrate specificity is conferred by adaptor proteins such as DDB1 and DCAF proteins. This modular architecture allows CRL4 to target a wide array of substrates, thereby influencing numerous cellular processes including cell cycle regulation, DNA repair, autophagy, and transcription. Researchers study CRL4 because of its central role in maintaining cellular homeostasis and its frequent dysregulation in human diseases, especially cancer. For example, CRL4-DCAF12 promotes lung cancer metastasis by modulating the TRiC/CCT chaperonin complex, and CRL4-AMBRA1 mediates progesterone receptor degradation, driving progestin resistance in endometrial cancer. Additionally, CRL4-Cdt2 regulates cell-cycle exit in concert with SCF-Fbxo11, and CRL4-AMBRA1 controls the stability of D-type cyclins. These findings underscore the importance of CRL4 as a therapeutic target and a subject of intense biomedical research. This article provides a comprehensive overview of GO:0080008, covering its definition, structure, molecular mechanism, key genes, disease associations, and research methodologies, with a focus on CRISPR-based approaches for functional interrogation.
Cul4-RING E3 ubiquitin ligase complex At A Glance
| GO ID | GO:0080008 |
|---|---|
| GO term | Cul4-RING E3 ubiquitin ligase complex |
| Ontology | cellular_component |
| Synonym | None |
| Major function | Catalyzes ubiquitination of substrate proteins, often leading to proteasomal degradation, thereby regulating diverse cellular processes. |
| Catalytic core | CUL4 family cullin and a RING-domain protein (e.g., RBX1). |
| Substrate adaptors | DDB1 and DCAF proteins confer substrate specificity. |
| Subcellular localization | Nucleus and cytoplasm, depending on complex composition and context. |
| Associated processes | Cell cycle, DNA damage response, autophagy, transcription, metabolism. |
What Is GO:0080008?
GO:0080008 describes a ubiquitin ligase complex in which a cullin from the Cul4 family and a RING domain protein form the catalytic core; substrate specificity is conferred by an adaptor protein.
Why Is Cul4-RING E3 ubiquitin ligase complex Important in Cell Biology?
The Cul4-RING E3 ubiquitin ligase complex is essential for regulated proteolysis, a fundamental mechanism controlling protein abundance and function in eukaryotic cells. By targeting specific substrates, CRL4 complexes influence cell-cycle progression, DNA replication, DNA repair, autophagy, and gene expression. Dysregulation of CRL4 components contributes to cancer, metabolic disorders, and developmental defects, making CRL4 an attractive target for therapeutic intervention. Understanding CRL4 biology is therefore critical for both basic research and translational medicine.
• Regulates cell-cycle progression by targeting substrates such as Cdt1 and D-type cyclins.
• Controls DNA damage responses and genome stability through degradation of key repair proteins.
• Modulates autophagy by ubiquitinating WIPI2 during mitosis.
• Influences adipogenesis and obesity onset via DDB1-BRWD3 interactions.
• Promotes lung cancer metastasis through DCAF12-mediated modulation of TRiC/CCT.
• Drives progestin resistance in endometrial cancer via AMBRA1-mediated progesterone receptor degradation.
• Serves as a paradigm for modular E3 ligase assembly and substrate recognition.
• Offers potential therapeutic targets for cancers with aberrant CRL4 activity.
• Enables CRISPR-based functional genomics to dissect subunit-specific roles.
• Provides insights into ubiquitin signaling networks and drug discovery.
Structure and Composition of Cul4-RING E3 ubiquitin ligase complex
Catalytic Core: CUL4 and RBX1
In simple terms: The core is like the engine of the complex, made of CUL4 and RBX1 proteins.
The catalytic core of CRL4 consists of a CUL4 family cullin protein and a RING-domain protein, typically RBX1 (also known as ROC1). CUL4 serves as a scaffold that assembles the complex, while RBX1 recruits the E2 ubiquitin-conjugating enzyme to facilitate ubiquitin transfer to substrates.
Adaptor Protein DDB1
In simple terms: DDB1 acts as a bridge connecting the core to substrate receptors.
DDB1 (DNA damage-binding protein 1) is a large adaptor protein that binds to the N-terminal region of CUL4 and serves as a platform for the assembly of DCAF substrate receptors. DDB1 is essential for the stability and function of many CRL4 complexes.
Substrate Receptors: DCAF Proteins
In simple terms: DCAF proteins are the 'hands' that grab specific target proteins.
DCAF (DDB1- and CUL4-associated factor) proteins constitute a large family of substrate receptors that bind to DDB1 and recognize specific substrates. Each DCAF confers distinct substrate specificity, allowing CRL4 to target a diverse array of proteins. Examples include DCAF1, DCAF12, and AMBRA1.
Dimerization and Higher-Order Assembly
In simple terms: Some CRL4 complexes can pair up to form dimers, which may affect their activity.
The CRL4-DCAF1 complex can dimerize via a short helical region in DCAF1, suggesting that higher-order assembly may regulate CRL4 function. Dimerization could influence substrate recognition, catalytic efficiency, or interactions with other cellular factors.
Dynamic Regulation by CAND1 and NEDD8
In simple terms: The complex is constantly being remodeled by other proteins to control its activity.
CRL4 activity is dynamically regulated by CAND1, which promotes the exchange of substrate receptors, and by NEDD8 modification of the cullin, which enhances ubiquitin ligase activity. These regulatory mechanisms ensure proper substrate targeting in response to cellular signals.
Key Genes Involved in GO:0080008 Cul4-RING E3 ubiquitin ligase complex
The following genes encode core components, adaptors, and substrate receptors of the Cul4-RING E3 ubiquitin ligase complex, as well as key substrates and regulators.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CUL4A | Cullin scaffold in CRL4 complex | Frequently overexpressed in cancers; target for knockout studies. |
| CUL4B | Cullin scaffold in CRL4 complex | Mutations cause X-linked intellectual disability; studied in neurodevelopment. |
| RBX1 | RING-domain protein, recruits E2 | Essential for catalytic activity; knockout is lethal. |
| DDB1 | Adaptor linking CUL4 to DCAFs | Required for CRL4 assembly; involved in DNA repair and adipogenesis. |
| DCAF1 | Substrate receptor | Regulates cell cycle and HIV infection; dimerization studied. |
| DCAF12 | Substrate receptor | Promotes lung cancer metastasis via TRiC/CCT. |
| AMBRA1 | Substrate receptor | Regulates autophagy, D-type cyclins, and progesterone receptor. |
| Cdt2 | Substrate receptor | Targets Cdt1 for degradation; regulates cell cycle. |
| WIPI2 | Substrate of CRL4 | Ubiquitinated during mitosis to suppress autophagy. |
| BRWD3 | Histone reader, interacts with DDB1 | Activates transcriptional cascade in adipogenesis. |
| CAND1 | Regulator of CRL4 assembly | Promotes substrate receptor exchange. |
| NEDD8 | Ubiquitin-like modifier | Modifies CUL4 to activate CRL4. |
| CDT1 | Substrate of CRL4-Cdt2 | Degraded to prevent re-replication. |
| Cyclin D1 | Substrate of CRL4-AMBRA1 | Regulates cell-cycle progression. |
| Progesterone receptor | Substrate of CRL4-AMBRA1 | Degradation drives progestin resistance. |
| TRiC/CCT | Chaperonin complex modulated by DCAF12 | Influences lung cancer metastasis. |
How Is Cul4-RING E3 ubiquitin ligase complex Regulated?
CRL4 activity is regulated at multiple levels. Cullin neddylation by the NEDD8 pathway enhances ubiquitin ligase activity, while CAND1 binding promotes the exchange of substrate receptors. Additionally, CRL4 complexes can be regulated by phosphorylation, dimerization, and interactions with inhibitory proteins. For example, the SCF-Fbxo11 ubiquitin ligase regulates CRL4-Cdt2 to control cell-cycle exit. These regulatory mechanisms ensure that CRL4 substrates are targeted appropriately in response to cellular cues.
Cul4-RING E3 ubiquitin ligase complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| DCAF12 | Lung cancer metastasis | Knockout in lung cancer cell lines; metastasis assays. |
| AMBRA1 | Endometrial cancer, progestin resistance | Knockout in endometrial cancer cells; drug response. |
| CUL4B | X-linked intellectual disability | Knockout mice; neuronal differentiation. |
| Cdt2 | Cell-cycle deregulation, cancer | Knockout in cancer cell lines; cell-cycle analysis. |
| DDB1 | Obesity, adipogenesis | Knockout in preadipocytes; differentiation assays. |
Cancer
Dysregulation of CRL4 components is frequently observed in human cancers. DCAF12 promotes lung cancer metastasis by modulating the TRiC/CCT chaperonin complex. CRL4-AMBRA1 mediates progesterone receptor degradation, driving progestin resistance in endometrial cancer. CRL4-AMBRA1 also regulates D-type cyclins, which are critical for cell-cycle progression and are often overexpressed in cancers. These findings highlight CRL4 as a potential therapeutic target in oncology.
Cell Cycle and Genome Stability
CRL4-Cdt2 targets Cdt1 for degradation, preventing DNA re-replication and maintaining genome stability. The SCF-Fbxo11 ligase regulates CRL4-Cdt2 to control cell-cycle exit, linking CRL4 to cell-cycle checkpoints. Disruption of these processes can lead to genomic instability and tumorigenesis.
Autophagy and Metabolism
CRL4-mediated ubiquitination of WIPI2 during mitosis suppresses autophagy, connecting CRL4 to cellular stress responses. Additionally, DDB1 interacts with the histone reader BRWD3 to activate a transcriptional cascade in adipogenesis, promoting obesity onset. These roles implicate CRL4 in metabolic regulation and autophagy-related diseases.
From Cul4-RING E3 ubiquitin ligase complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the role of CUL4A in cell proliferation? | CUL4A knockout cell lines (e.g., HCT116). |
| How does DCAF12 promote metastasis? | DCAF12 knockout in lung cancer cells; in vivo metastasis models. |
| Does AMBRA1 degradation of progesterone receptor cause progestin resistance? | AMBRA1 knockout in endometrial cancer cells; progesterone treatment. |
| What is the effect of CUL4B mutation on neuronal development? | CUL4B point-mutation knock-in mice. |
| How does DDB1-BRWD3 interaction regulate adipogenesis? | DDB1 knockout in preadipocytes; RNA-seq. |
| Can CRL4-Cdt2 be targeted to inhibit cancer growth? | Cdt2 knockout in cancer cell lines; xenograft models. |
How to Study the Cul4-RING E3 ubiquitin ligase complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| CRISPR knockout screen | Gene essentiality and drug resistance | Identify CRL4 components required for cancer cell growth. |
| Proteomics | Protein interactions and ubiquitination | Map CRL4 substrate networks. |
| RNA-seq | Transcriptional changes | Assess downstream effects of CRL4 perturbation. |
| Western blot | Protein stability and degradation | Validate substrate degradation by CRL4. |
| Immunoprecipitation | Complex assembly and interactions | Study DDB1-DCAF interactions. |
| Cell-cycle analysis | DNA content and proliferation | Evaluate CRL4 role in cell-cycle progression. |
| Autophagy flux assay | Autophagosome turnover | Study CRL4-mediated WIPI2 degradation. |
| Xenograft models | Tumor growth and metastasis | Test CRL4 targeting in vivo. |
CRISPR-Cas9 Knockout Screens
Genome-wide CRISPR knockout screens can identify essential CRL4 components and substrate receptors in various cell types. These screens use lentiviral sgRNA libraries to disrupt genes and assess effects on cell fitness, drug resistance, or metastasis.
Proteomics and Ubiquitinome Analysis
Mass spectrometry-based proteomics can identify CRL4 substrates and interactors by comparing wild-type and knockout cells. Ubiquitin remnant profiling can map specific ubiquitination sites on substrates.
RNA Sequencing (RNA-seq)
RNA-seq reveals transcriptional changes upon CRL4 perturbation, uncovering downstream pathways. For example, DDB1 knockout in adipocytes affects expression of metabolic genes.
Imaging and Cell-Based Assays
Fluorescence microscopy can visualize CRL4 localization and substrate degradation in live cells. Cell-cycle analysis and autophagy flux assays are used to study CRL4 functions.
How CRISPR Can Be Used to Study GO:0080008 Cul4-RING E3 ubiquitin ligase complex
Knockout
CRISPR-Cas9 knockout of CRL4 subunits (e.g., CUL4A, DDB1, DCAF12) is used to abolish complex function and assess cellular phenotypes. Knockout cell lines are valuable for identifying substrates and pathways dependent on CRL4.
Point Mutation
Point mutations can be introduced into CRL4 genes to dissect specific domains or catalytic residues. For example, mutating the RING domain of RBX1 or the cullin neddylation site can reveal their roles in ubiquitin transfer.
Knock-in
Knock-in of tagged CRL4 components (e.g., GFP-CUL4A) allows for live-cell imaging and affinity purification of complexes. Knock-in of disease-associated mutations (e.g., CUL4B) can model human disorders.
Overexpression
Overexpression of CRL4 subunits or substrate receptors can amplify complex activity and enhance substrate degradation, useful for studying gain-of-function effects in cancer. Inducible overexpression systems provide temporal control.
How EDITGENE Supports Cul4-RING E3 ubiquitin ligase complex Research
Researchers studying Cul4-RING E3 ubiquitin ligase complex-related genes often need to determine whether a candidate gene is causally involved in a specific cellular process or disease. EDITGENE provides comprehensive CRISPR-based services to enable precise genetic manipulation and functional interrogation of CRL4 components.
Contact EDITGENE today to design your custom CRISPR model for Cul4-RING E3 ubiquitin ligase complex research.
Frequently Asked Questions About Cul4-RING E3 ubiquitin ligase complex
What is the Cul4-RING E3 ubiquitin ligase complex?
It is a multi-subunit E3 ubiquitin ligase complex (GO:0080008) that catalyzes ubiquitin transfer to specific substrates, with a catalytic core of CUL4 and a RING protein, and substrate specificity provided by adaptor proteins.
What genes are involved in the Cul4-RING E3 ubiquitin ligase complex?
Key genes include CUL4A, CUL4B, RBX1, DDB1, and various DCAF genes such as DCAF1, DCAF12, and AMBRA1.
What is the function of CRL4 in the cell?
CRL4 regulates cell-cycle progression, DNA damage responses, autophagy, transcription, and metabolism by targeting specific proteins for ubiquitination and degradation.
How is the Cul4-RING E3 ubiquitin ligase complex regulated?
It is regulated by cullin neddylation, CAND1-mediated receptor exchange, phosphorylation, and dimerization.
What diseases are associated with CRL4 dysfunction?
CRL4 dysregulation is linked to cancers such as lung cancer and endometrial cancer, as well as X-linked intellectual disability and metabolic disorders.
What are the substrates of CRL4?
Substrates include Cdt1, D-type cyclins, WIPI2, progesterone receptor, and TRiC/CCT, among others.
How can CRISPR be used to study CRL4?
CRISPR knockout, point mutation, knock-in, and overexpression models allow precise dissection of CRL4 subunit functions and substrate interactions.
What is the role of DCAF proteins in CRL4?
DCAF proteins are substrate receptors that bind to DDB1 and recognize specific substrates, conferring substrate specificity to the CRL4 complex.
Is CRL4 a potential drug target?
Yes, CRL4 components are considered promising therapeutic targets, especially in cancers where they are dysregulated.
What methods are used to study CRL4?
Common methods include CRISPR screens, proteomics, RNA-seq, western blot, immunoprecipitation, and cell-based assays.
Conclusion
The Cul4-RING E3 ubiquitin ligase complex (GO:0080008) is a critical regulator of protein homeostasis, controlling diverse cellular processes through targeted ubiquitination. Its modular architecture and numerous substrate receptors enable precise regulation of cell cycle, DNA repair, autophagy, and metabolism. Dysregulation of CRL4 is implicated in cancer and other diseases, making it an attractive therapeutic target. Continued research using advanced CRISPR models and functional genomics will further elucidate CRL4 biology and its potential for clinical translation.
References
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