GO:1990112 RQC complex: Components, Assembly and Research Methods, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:1990112 (RQC complex) is a conserved multiprotein machine that recognizes stalled 60S ribosomal subunits and targets the nascent polypeptide for degradation.
• The complex is defined by core factors including Cdc48p/VCP, Rkr1p/LTN1, Tae2p, Rqc1p, Npl4p and Ufd1p in budding yeast, with orthologous systems in humans.
• RQC complex assembly is triggered by ribosome collisions and involves the dissociation of stalled 80S ribosomes by the RQT complex.
• Polyubiquitin chain architecture on collided ribosomes is dynamically edited to maintain persistent RQC activity.
• RQC complex dysfunction is linked to neurodegeneration, cancer and ribosomopathies, making it a target for therapeutic intervention.
• CRISPR knockout, point mutation, knock-in and overexpression models are essential to dissect RQC gene function and validate drug targets.
Description
The RQC complex (GO:1990112) is a cellular component that forms a stable complex with large ribosomal subunits containing stalled polypeptides and triggers their degradation, a process known as ribosomal quality control. This complex is conserved from bacteria to humans and is essential for maintaining proteostasis by eliminating aberrant nascent chains that would otherwise aggregate and impair cellular function. In budding yeast, the RQC complex includes Cdc48p, Rkr1p, Tae2p, Rqc1p, Npl4p and Ufd1p proteins. The RQC complex is not merely a degradation machine; it also signals translation stress to the cell, coordinating translational repression with protein quality control. Researchers study this complex to understand how cells cope with ribosome collisions, a common event during translation of problematic mRNAs, and how defects in this pathway contribute to human disease.
RQC complex At A Glance
| GO ID | GO:1990112 |
|---|---|
| GO term | RQC complex |
| Ontology | cellular_component |
| Synonym | ribosome-bound quality control complex, ribosome quality control complex |
| Major function | Triggers degradation of stalled polypeptides on large ribosomal subunits |
| Major components | Cdc48p, Rkr1p, Tae2p, Rqc1p, Npl4p, Ufd1p (budding yeast) |
| Conservation | Eukaryotes and prokaryotes |
| Related process | Ribosome-associated protein quality control (RQC) |
What Is GO:1990112?
The RQC complex is a multiprotein assembly that binds to large ribosomal subunits (60S in eukaryotes, 50S in prokaryotes) that have stalled during translation and carry a nascent polypeptide. This binding triggers the degradation of the stalled polypeptide, thereby preventing the accumulation of toxic protein aggregates. The complex is a key component of ribosomal quality control (RQC) and is conserved across species.
Why Is RQC complex Important in Cell Biology?
The RQC complex is critical for protein homeostasis because it eliminates potentially toxic nascent polypeptides that stall on ribosomes. Defects in RQC lead to the accumulation of aggregation-prone proteins, which are hallmarks of neurodegenerative diseases such as amyotrophic lateral sclerosis and Alzheimer's disease. Furthermore, the RQC pathway is emerging as a modulator of cancer cell survival under proteotoxic stress, and its components are being explored as therapeutic targets.
• Prevents aggregation of stalled polypeptides, protecting cells from proteotoxicity.
• Signals translation stress to coordinate global translational repression.
• Implicated in neurodegeneration due to failure to clear aberrant proteins.
• Plays a role in cancer cell adaptation to stress.
• Conserved mechanism from yeast to humans, enabling model organism studies.
• Interacts with UFMylation pathway at the endoplasmic reticulum.
• Regulates ribosome collision response and ribosome dissociation.
• Polyubiquitin chain editing ensures sustained RQC activity.
• Potential target for therapies against ribosomopathies.
• Key to understanding translational quality control in aging.
What Happens During RQC complex?
Ribosome collision and stalling
In simple terms: When a ribosome gets stuck while making a protein, another ribosome can bump into it, forming a collision.
Ribosome collisions occur when a translating ribosome stalls on a problematic mRNA, such as one lacking a stop codon or containing rare codons. The collision is recognized by the RQC complex, which is recruited to the stalled 60S subunit. The RQT complex (Ribosome Quality Control Trigger) dissociates the collided ribosomes, allowing the 60S subunit to be accessed by RQC factors.
Recognition and ubiquitination of stalled nascent chains
In simple terms: The stuck protein is tagged with a chain of ubiquitin molecules, marking it for destruction.
The RQC complex recognizes the stalled nascent polypeptide and recruits E3 ubiquitin ligases, such as Rkr1p/LTN1, to attach ubiquitin chains to the nascent chain. The polyubiquitin architecture is dynamically edited to maintain persistent RQC activity. This ubiquitination serves as a signal for downstream extraction and degradation.
Extraction and degradation of the stalled polypeptide
In simple terms: The tagged protein is pulled out of the ribosome and chopped up by the proteasome.
The AAA-ATPase Cdc48p (VCP/p97 in humans) in complex with Npl4p and Ufd1p extracts the ubiquitinated nascent chain from the 60S subunit. The extracted polypeptide is then delivered to the proteasome for degradation. This process requires the coordinated action of the RQC complex components and is essential for preventing aggregation.
Signaling translation stress
In simple terms: The cell senses that something is wrong with translation and slows down protein production.
The RQC complex also signals translation stress by activating pathways that repress global translation. In yeast, this involves the phosphorylation of eIF2α, which reduces initiation of translation. This feedback mechanism allows the cell to recover from stress and avoid further collisions.
Key Genes Involved in GO:1990112 RQC complex
The following genes and proteins are core components or regulators of the RQC complex, based on studies in budding yeast and higher eukaryotes.
| Gene | Major Role | Research Relevance |
|---|---|---|
| CDC48 (VCP/p97) | AAA-ATPase that extracts ubiquitinated nascent chains from 60S subunits | Central to RQC; mutations linked to neurodegeneration |
| RKR1 (LTN1) | E3 ubiquitin ligase that ubiquitinates stalled nascent chains | Key for substrate tagging; knockout leads to RQC deficiency |
| TAE2 (NEMF) | Ribosome-binding protein that recruits RQC factors | Essential for RQC assembly; mutations affect stress response |
| RQC1 | Component of RQC complex, involved in signaling and degradation | Required for RQC function; not a target of the complex |
| NPL4 | Cofactor of Cdc48p for substrate extraction | Essential for retrotranslocation; knockdown impairs RQC |
| UFD1 | Cofactor of Cdc48p, forms complex with Npl4p | Required for extraction of stalled chains |
| RQT4 (SDD1) | Substrate of RQC; involved in ribosome dissociation | Model substrate for studying RQC |
| LTN1 (human) | Human ortholog of Rkr1p | Implicated in neurodegeneration and cancer |
| NEMF (human) | Human ortholog of Tae2p | Mutations linked to neuromuscular disease |
| VCP (human) | Human ortholog of Cdc48p | Mutations cause IBMPFD and ALS |
| UFM1 | Ubiquitin-like modifier involved in ER stress response | Cooperates with RQC at the ER |
| UBA5 | E1 enzyme for UFMylation | Regulates UFMylation and RQC crosstalk |
| UFC1 | E2 enzyme for UFMylation | Modulates RQC pathway |
| UFL1 | E3 ligase for UFMylation | Links UFMylation to RQC |
| RPL28 | 60S ribosomal protein | Mutations affect RQC substrate recognition |
| RPS3 | 40S ribosomal protein | Involved in collision recognition |
| HEL2 | RNA helicase involved in RQC | Facilitates ribosome dissociation |
| SLH1 | RNA helicase in RQT complex | Required for ribosome splitting |
How Is RQC complex Regulated?
The RQC complex is regulated at multiple levels. Translation stress activates the integrated stress response (ISR), which phosphorylates eIF2α and reduces global translation, thereby limiting ribosome collisions. The UFMylation pathway at the endoplasmic reticulum coordinates with RQC to clear arrested polypeptides, and UFM1 modification of ribosomal proteins regulates RQC activity. Polyubiquitin chain editing by deubiquitinases and E3 ligases dynamically controls the persistence of RQC signaling. Additionally, the availability of ATP and the proteasome capacity influence the efficiency of substrate extraction and degradation.
RQC complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| VCP | IBMPFD, ALS | Knock-in of patient mutations in cell lines; KO in neurons |
| LTN1 | Neurodegeneration | KO in mouse models; point mutations in human iPSCs |
| NEMF | Neuromuscular disease | Knock-in of patient variants; overexpression in zebrafish |
| UFM1 | ER stress-related disorders | KO in HeLa cells; knock-in of UFM1 mutations |
| RPL28 | Ribosomopathy | Point mutation in yeast; KO in human cells |
Neurodegeneration
Mutations in VCP, the human ortholog of Cdc48p, cause inclusion body myopathy with Paget's disease of bone and frontotemporal dementia (IBMPFD) and amyotrophic lateral sclerosis (ALS). These mutations impair RQC-mediated clearance of stalled polypeptides, leading to protein aggregation and neuronal death. Similarly, defects in LTN1 and NEMF are associated with neurodegenerative phenotypes in model organisms.
Cancer
Cancer cells often experience high proteotoxic stress due to rapid proliferation and aneuploidy. The RQC complex helps cancer cells survive this stress by clearing stalled polypeptides. Inhibition of RQC components, such as VCP, has shown anti-tumor activity in preclinical models, making RQC a potential therapeutic target.
Ribosomopathies
Ribosomopathies are diseases caused by defects in ribosome biogenesis or function. Mutations in ribosomal proteins or RQC factors can lead to bone marrow failure and developmental abnormalities. The RQC complex is thought to mitigate the effects of defective ribosomes by degrading aberrant nascent chains.
From RQC complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does gene X regulate RQC activity? | CRISPR knockout in HEK293 or yeast |
| Does mutation Y affect RQC substrate recognition? | Point mutation knock-in in cell lines |
| How does gene X localize during RQC? | Tagged knock-in with fluorescent protein |
| Does overexpression of gene X rescue RQC defects? | Overexpression via lentiviral transduction |
| Which genes are essential for RQC in a genome-wide screen? | CRISPR library screening |
| What is the transcriptomic response to RQC inhibition? | RNA-seq after knockout |
How to Study the RQC complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Ribo-seq | Ribosome positions and collisions | Detect stalling and RQC targets |
| Proteomics | Protein interactions and ubiquitination | Identify RQC components and substrates |
| Fluorescence microscopy | Localization and assembly of RQC factors | Visualize complex formation |
| CRISPR knockout screening | Genes required for RQC | Discover novel RQC regulators |
| RNA-seq | Transcriptional changes | Measure stress response activation |
| Co-immunoprecipitation | Protein-protein interactions | Validate RQC complex composition |
| In vitro ubiquitination assays | Ubiquitin chain formation | Study E3 ligase activity |
| Polysome profiling | Ribosome distribution on mRNAs | Assess translation repression |
Ribosome profiling (Ribo-seq)
Ribo-seq provides a snapshot of ribosome positions on mRNAs at codon resolution. It is used to detect ribosome collisions and stalling, which are triggers for RQC complex recruitment. By comparing wild-type and RQC mutant cells, researchers can identify specific mRNAs that rely on RQC for quality control.
Proteomics and ubiquitin chain analysis
Mass spectrometry-based proteomics can identify proteins associated with the RQC complex and quantify ubiquitination sites on stalled nascent chains. This approach reveals the architecture of polyubiquitin chains and how they are edited during RQC.
Fluorescence microscopy and imaging
Live-cell imaging of fluorescently tagged RQC components (e.g., Cdc48p, Rqc1p) allows visualization of complex assembly at stalled ribosomes. Co-localization with ribosomal markers and proteasome subunits can confirm functional interactions.
CRISPR screening and functional genomics
Genome-wide CRISPR knockout screens can identify genes that are essential for RQC-mediated degradation. Cells expressing a reporter with a stall-inducing sequence are used to select for RQC-deficient mutants, followed by next-generation sequencing to identify enriched sgRNAs.
How CRISPR Can Be Used to Study GO:1990112 RQC complex
Knockout
CRISPR knockout of RQC genes (e.g., CDC48, RKR1, TAE2) in cell lines or model organisms abolishes RQC activity, leading to accumulation of stalled polypeptides. These models are used to study the physiological consequences of RQC loss and to identify synthetic lethal interactions.
Point Mutation
Point mutations in RQC genes, such as those found in patients with VCP mutations, can be introduced via CRISPR to model disease-associated dysfunction. These knock-in models help dissect the specific roles of catalytic residues or interaction domains.
Knock-in
Knock-in of tagged versions of RQC components (e.g., GFP-Cdc48) allows real-time tracking of complex assembly and dynamics. This approach is valuable for understanding the spatiotemporal regulation of RQC.
Overexpression
Overexpression of RQC genes or their substrates can be achieved by CRISPR activation or lentiviral delivery. This is useful for testing whether increased RQC activity can rescue proteotoxicity in disease models.
How EDITGENE Supports RQC complex Research
Researchers studying RQC complex-related genes often need to determine whether a candidate gene is causally involved in ribosomal quality control, how mutations affect complex assembly, and whether modulating its activity can rescue disease phenotypes. EDITGENE provides a comprehensive suite of CRISPR-based services to address these questions with precision and reproducibility.
Contact EDITGENE today to design your custom CRISPR model for RQC complex research.
Frequently Asked Questions About RQC complex
What is the RQC complex?
The RQC complex (GO:1990112) is a multiprotein machine that binds to stalled ribosomes and triggers degradation of the incomplete polypeptide, preventing toxic aggregation.
What genes are involved in the RQC complex?
Core genes include CDC48, RKR1, TAE2, RQC1, NPL4, and UFD1 in yeast, with human orthologs VCP, LTN1, NEMF, and others.
What is the function of GO:1990112?
GO:1990112 is a cellular component that mediates ribosomal quality control by recognizing stalled 60S subunits and targeting nascent chains for proteasomal degradation.
How is the RQC complex regulated?
It is regulated by translation stress, UFMylation, and polyubiquitin chain editing, which ensure sustained activity and crosstalk with other quality control pathways.
What diseases are associated with RQC complex dysfunction?
Neurodegeneration (ALS, IBMPFD), cancer, and ribosomopathies have been linked to defects in RQC components such as VCP and LTN1.
What methods are used to study the RQC complex?
Common methods include Ribo-seq, proteomics, fluorescence microscopy, and CRISPR screening to identify components and substrates.
Can CRISPR be used to study RQC genes?
Yes, CRISPR knockout, point mutation knock-in, and overexpression models are widely used to dissect RQC gene function and disease mechanisms.
What is the role of Cdc48p in the RQC complex?
Cdc48p (VCP in humans) is an AAA-ATPase that extracts ubiquitinated nascent chains from the 60S subunit for proteasomal degradation.
How does the RQC complex recognize stalled ribosomes?
It recognizes ribosome collisions and stalled 60S subunits through factors like Tae2p and Rqc1p, which recruit downstream effectors.
What is the difference between RQC and RQT?
RQT dissociates collided ribosomes, while RQC degrades the stalled nascent chain; they act sequentially in ribosome quality control.
Conclusion
The RQC complex (GO:1990112) is a central player in ribosomal quality control, essential for clearing stalled polypeptides and maintaining proteostasis. Its dysfunction is linked to severe human diseases, including neurodegeneration and cancer. Understanding its mechanisms through CRISPR-based models and advanced screening technologies will pave the way for novel therapeutic strategies. EDITGENE is committed to providing the tools and expertise needed to accelerate this research.
References
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- 2. Matsuo Y et al.. 2020. RQT complex dissociates ribosomes collided on endogenous RQC substrate SDD1.. Nat Struct Mol Biol 27(4):323-332 PMID: 32203490
- 3. Inada T et al.. 2024. Mechanisms of Translation-coupled Quality Control.. J Mol Biol 436(6):168496 PMID: 38365086
- 4. Tomomatsu S et al.. 2025. Polyubiquitin architecture editing on collided ribosomes maintains persistent RQC activity.. EMBO J 44(21):6051-6077 PMID: 40957981
- 5. Barros GC et al.. 2021. Rqc1 and other yeast proteins containing highly positively charged sequences are not targets of the RQC complex.. J Biol Chem 296:100586 PMID: 33774050
- 6. Mihailovic M et al.. 2026. The coordinated action of UFMylation and the RQC pathways clears arrested polypeptides at the ER.. EMBO J 45(9):3252-3275 PMID: 41882226
- 7. Brandman O et al.. 2012. A ribosome-bound quality control complex triggers degradation of nascent peptides and signals translation stress.. Cell 151(5):1042-54 PMID: 23178123
- 8. Chang WD et al.. 2024. Threonine-rich carboxyl-terminal extension drives aggregation of stalled polypeptides.. Mol Cell 84(22):4334-4349.e7 PMID: 39488212
