GO:0022625 cytosolic large ribosomal subunit: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0022625 defines the large subunit of the ribosome located in the cytosol, also known as the 60S subunit in eukaryotes and the 50S subunit in prokaryotes.
• The cytosolic large ribosomal subunit (LSU) catalyzes peptide bond formation and coordinates the exit tunnel for nascent polypeptides.
• Its assembly requires a cascade of transient assembly factors, including the AAA+ ATPase SPATA5, which drives pre-60S maturation in human cells.
• Ribosomal RNA expansion segments in the LSU fine-tune translation and provide binding platforms for regulatory factors.
• Dysregulation of LSU biogenesis is linked to ribosomopathies, cancer, and developmental disorders.
• CRISPR-based knockout, point mutation, and knock-in models enable causal dissection of LSU protein function in human cells.
Description
The cytosolic large ribosomal subunit (GO:0022625) is the major catalytic component of the ribosome, responsible for peptide bond formation during protein synthesis. In eukaryotes, this subunit is termed the 60S subunit, while in prokaryotes it is the 50S subunit; both are located in the cytosol and share a conserved core structure. The LSU comprises ribosomal RNA (rRNA) and dozens of ribosomal proteins that together form the peptidyl transferase center, the exit tunnel, and multiple interaction sites for translation factors. Understanding its composition and assembly is fundamental to deciphering how cells regulate gene expression at the translational level. Recent advances in cryo-electron microscopy and genetic screens have revealed that LSU biogenesis is a highly dynamic process requiring numerous assembly factors, including the AAA+ ATPase SPATA5, which couples ATP hydrolysis to pre-60S maturation. In plants, the nuclear envelope and mitochondria-localized OPENER complex is required for ribosome biogenesis, highlighting the integration of LSU assembly with cellular architecture. Furthermore, the function of assembly factors such as Mak16 depends on iron-sulfur cluster cofactors, linking LSU biogenesis to cellular metabolism. These findings underscore the importance of GO:0022625 in both basic cell biology and disease mechanisms. For researchers, the cytosolic large ribosomal subunit represents a tractable system to study translation, ribosome assembly, and the action of antibiotics and chemotherapeutic agents. Mutations in LSU components or assembly factors cause ribosomopathies, and altered LSU function is observed in cancer and neurodegeneration. This article provides a comprehensive overview of the structure, function, regulation, and research methods for studying GO:0022625, with a focus on CRISPR-based models for functional genomics.
cytosolic large ribosomal subunit At A Glance
| GO ID | GO:0022625 |
|---|---|
| GO term | cytosolic large ribosomal subunit |
| Ontology | cellular_component |
| Synonym | 50S ribosomal subunit, 60S ribosomal subunit, eukaryotic ribosomal LSU, prokaryotic large ribosomal subunit |
| Major function | Catalyzes peptide bond formation during protein synthesis and forms the exit tunnel for nascent polypeptides |
| Location | Cytosol |
| Composition | Ribosomal RNA and ribosomal proteins; in eukaryotes, the 60S subunit contains 28S, 5.8S, and 5S rRNA plus ~47 proteins |
| Assembly factors | SPATA5, Mak16, OPENER complex, and other transient factors |
| Related diseases | Ribosomopathies, cancer, developmental disorders |
What Is GO:0022625?
GO:0022625, cytosolic large ribosomal subunit, is defined by QuickGO as the large subunit of a ribosome located in the cytosol. It is the larger of the two ribosomal subunits and contains the peptidyl transferase center, where amino acids are joined into polypeptides. In eukaryotes, it is commonly referred to as the 60S subunit, while in prokaryotes it is the 50S subunit. The subunit consists of ribosomal RNA and many ribosomal proteins, and it functions together with the small subunit to translate messenger RNA into protein.
Why Is cytosolic large ribosomal subunit Important in Cell Biology?
The cytosolic large ribosomal subunit is essential for all cellular protein synthesis and thus for cell growth, proliferation, and survival. Its dysfunction or dysregulation is directly linked to human diseases, including ribosomopathies such as Diamond-Blackfan anemia and Shwachman-Diamond syndrome, as well as cancer and neurodegeneration. Moreover, the LSU is the target of many clinically important antibiotics, such as tigecycline, which binds to the mitochondrial ribosome and causes T cell toxicity. Studying GO:0022625 therefore provides critical insights into fundamental biology and therapeutic development.
• Central to translation: the LSU catalyzes peptide bond formation, making it indispensable for protein synthesis.
• Ribosomopathies: mutations in LSU proteins or assembly factors cause bone marrow failure and developmental defects.
• Cancer: altered LSU biogenesis supports rapid proliferation of cancer cells and is a potential therapeutic target.
• Antibiotic targeting: the LSU is the binding site for antibiotics like tigecycline, with implications for T cell toxicity.
• Mitochondrial crosstalk: cytosolic and mitochondrial ribosomal proteins coordinate translational profiles during locust phase transition.
• Assembly factor dependencies: SPATA5 and Mak16 are essential for LSU maturation, linking biogenesis to ATP and iron-sulfur metabolism.
• rRNA expansion segments: these LSU features modulate translation and factor recruitment.
• Plant development: the OPENER complex connects nuclear envelope and mitochondria to LSU biogenesis in plants.
• Trypanosome-specific processing: a unique complex mediates late-stage LSU rRNA processing in trypanosomes.
• Therapeutic potential: targeting LSU assembly or function may yield new treatments for infections and cancer.
What Happens During cytosolic large ribosomal subunit?
Transcription and Processing of LSU rRNA
In simple terms: The cell first makes a long ribosomal RNA molecule that is cut and trimmed to form the RNA backbone of the large subunit.
In eukaryotes, the 35S or 47S pre-rRNA transcript is processed to yield the mature 28S, 5.8S, and 5S rRNAs of the 60S subunit. This processing requires numerous endonucleases and exonucleases, as well as small nucleolar RNAs. In trypanosomes, a specific complex mediates late-stage processing of cytosolic LSU rRNA, highlighting evolutionary diversity in this step. The rRNA forms the structural core and catalytic center of the LSU.
Assembly of Ribosomal Proteins onto rRNA
In simple terms: Proteins attach to the RNA scaffold in a precise order to build the large subunit.
Ribosomal proteins are imported into the nucleus, where they assemble with pre-rRNA. In mammalian cells, the assembly of the 60S subunit involves the sequential addition of proteins and transient assembly factors. The AAA+ ATPase SPATA5 drives late pre-60S maturation, and its dysfunction impairs LSU assembly. Mak16, a conserved assembly factor, requires an iron-sulfur cluster for its function, linking assembly to cellular iron homeostasis.
Nuclear Export and Cytosolic Maturation
In simple terms: The nearly finished large subunit travels out of the nucleus and undergoes final maturation steps in the cytosol.
After assembly in the nucleus, pre-60S particles are exported to the cytosol through nuclear pore complexes. In plants, the nuclear envelope and mitochondria-localized OPENER complex is required for ribosome biogenesis, suggesting spatial coordination between organelles. In the cytosol, final maturation steps remove remaining assembly factors and prepare the LSU for translation.
Catalysis of Peptide Bond Formation
In simple terms: Once assembled, the large subunit acts as a molecular machine that links amino acids together to form proteins.
The mature LSU contains the peptidyl transferase center, which catalyzes the formation of peptide bonds between amino acids. This activity is mediated by the 28S rRNA in eukaryotes, making the ribosome a ribozyme. The LSU also forms the exit tunnel through which the nascent polypeptide emerges, and it interacts with translation factors such as EF-2 during translocation.
Quality Control and Degradation
In simple terms: If the large subunit is built incorrectly, the cell has surveillance systems to detect and destroy it.
Cells possess quality control mechanisms that monitor ribosome assembly and degrade defective pre-60S particles. The SPATA5 complex is involved in pre-60S maturation and may also participate in quality control. In trypanosomes, a specific complex ensures correct late-stage processing of LSU rRNA, and its failure leads to degradation. These pathways prevent the accumulation of faulty ribosomes that could impair translation fidelity.
Key Genes Involved in GO:0022625 cytosolic large ribosomal subunit
The following genes encode core ribosomal proteins and assembly factors that are essential for the structure and function of the cytosolic large ribosomal subunit.
| Gene | Major Role | Research Relevance |
|---|---|---|
| RPL3 | Core protein of the 60S subunit; forms part of the peptidyl transferase center | Mutations linked to ribosomopathies; target for functional studies |
| RPL4 | Structural component of the 60S subunit; interacts with rRNA | Required for LSU assembly; knockout causes lethality |
| RPL5 | Binds 5S rRNA and forms part of the central protuberance | Implicated in Diamond-Blackfan anemia |
| RPL11 | Interacts with 5S rRNA and MDM2; regulates p53 | Key role in ribosome stress signaling; cancer research |
| RPL23 | Binds 28S rRNA; part of the exit tunnel | Target for antibiotic studies; assembly factor interactions |
| RPL26 | Involved in LSU assembly and translation regulation | Linked to Diamond-Blackfan anemia and p53 activation |
| RPL35 | Structural protein of the 60S subunit | Mutations cause developmental defects; model for ribosomopathy |
| RPL38 | Required for translation of specific Hox mRNAs | Role in development; knockout mouse models |
| RPSA | Actually a small subunit protein, but included for context? No, must be LSU. Use RPLP0 | |
| RPLP0 | Forms the ribosomal stalk with RPLP1 and RPLP2 | Essential for translation factor recruitment; cancer target |
| RPLP1 | Acidic ribosomal protein; part of the stalk | Regulates translation elongation; overexpressed in cancers |
| RPLP2 | Acidic ribosomal protein; part of the stalk | Involved in translation and ribosome assembly |
| SPATA5 | AAA+ ATPase; drives pre-60S maturation | Mutations cause epilepsy, hearing loss, and developmental delay |
| MAK16 | Assembly factor with iron-sulfur cluster | Required for LSU biogenesis; links to iron metabolism |
| OPENER complex | Plant-specific complex for ribosome biogenesis | Connects nuclear envelope and mitochondria to LSU assembly |
| RPL10 | Component of the 60S subunit; involved in translation | Mutations linked to autism and cancer |
| RPL22 | Ribosomal protein with extra-ribosomal functions | Regulates development and immunity |
| RPL24 | Required for translation of specific mRNAs | Role in development and cancer |
How Is cytosolic large ribosomal subunit Regulated?
The biogenesis and function of the cytosolic large ribosomal subunit are regulated at multiple levels. Transcription of rRNA by RNA polymerase I is controlled by nutrient and growth factor signaling, including the mTOR pathway. Assembly factor expression and activity are also regulated; for example, SPATA5 ATPase activity is essential for pre-60S maturation and may be modulated by cellular energy status. In plants, the OPENER complex coordinates LSU assembly with mitochondrial function, suggesting metabolic regulation. Additionally, the integrated stress response can inhibit translation initiation, indirectly affecting LSU utilization. Ribosomal protein stoichiometry is tightly regulated; excess proteins are degraded, and imbalances trigger p53-mediated stress responses.
cytosolic large ribosomal subunit and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| RPL5 | Diamond-Blackfan anemia | Knockout in hematopoietic stem cells; zebrafish model |
| RPL11 | Diamond-Blackfan anemia; p53 activation | Knock-in of patient mutations in cell lines |
| SPATA5 | Epilepsy, hearing loss, developmental delay | Knockout mouse; patient-derived iPSCs |
| MAK16 | Ribosome biogenesis defects; iron metabolism | Point mutation of Fe-S cluster ligands |
| RPLP1 | Cancer progression; poor prognosis | Overexpression in cancer cell lines; xenograft |
Ribosomopathies and Bone Marrow Failure
Mutations in genes encoding cytosolic large ribosomal subunit proteins or assembly factors cause ribosomopathies, a group of disorders characterized by bone marrow failure, craniofacial anomalies, and increased cancer risk. For example, mutations in RPL5 and RPL11 are associated with Diamond-Blackfan anemia, while SPATA5 mutations cause epilepsy, hearing loss, and developmental delay. These diseases highlight the critical role of LSU biogenesis in human development and tissue homeostasis.
Cancer and Translational Reprogramming
Cancer cells often exhibit increased ribosome biogenesis to support rapid proliferation. Overexpression of LSU proteins such as RPLP1 and RPLP2 is observed in various cancers and correlates with poor prognosis. Targeting LSU assembly or function, for instance by inhibiting SPATA5, may offer therapeutic strategies. Additionally, the LSU is involved in selective translation of oncogenic mRNAs, making it a potential target for precision oncology.
Mitochondrial Ribosome and Drug Toxicity
Although GO:0022625 refers to the cytosolic LSU, there is crosstalk with mitochondrial ribosomes. The antibiotic tigecycline binds to the mitochondrial ribosome and causes T cell toxicity, illustrating how drugs targeting prokaryotic-like ribosomes can affect human cells. Understanding the differences between cytosolic and mitochondrial LSU is crucial for drug development.
Neurological and Developmental Disorders
Defects in LSU assembly factors such as SPATA5 lead to severe neurodevelopmental disorders, including epilepsy and hearing loss. In plants, the OPENER complex is required for ribosome biogenesis and development, and its dysfunction causes growth defects. These findings underscore the importance of LSU function in development and tissue-specific translation.
From cytosolic large ribosomal subunit-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does knockout of RPL5 impair LSU assembly? | CRISPR knockout in HEK293T cells followed by sucrose gradient analysis |
| What is the effect of a point mutation in SPATA5 on ATPase activity? | CRISPR point mutation knock-in in human cells |
| Can overexpression of RPLP1 drive oncogenic translation? | Doxycycline-inducible overexpression in cancer cell lines |
| How does Mak16 Fe-S cluster mutation affect LSU biogenesis? | CRISPR knock-in of cysteine-to-serine mutations |
| Does the OPENER complex localize to mitochondria during LSU assembly? | Tagged knock-in of OPENER subunits in plant cells |
| What is the role of RPL38 in Hox mRNA translation? | Knockout mouse model and ribosome profiling |
How to Study the cytosolic large ribosomal subunit Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Ribo-seq | Ribosome occupancy on mRNAs | Global translation efficiency; codon usage |
| Sucrose gradient | Distribution of ribosomal subunits and polysomes | LSU assembly defects; pre-60S accumulation |
| Cryo-EM | 3D structure of LSU at high resolution | Assembly factor binding; antibiotic interactions |
| CRISPR knockout screen | Gene essentiality and drug resistance | Identify LSU assembly factors and disease modifiers |
| Mass spectrometry | Protein composition of LSU | Identify novel ribosomal proteins and modifications |
| Northern blot | rRNA processing intermediates | Monitor LSU rRNA maturation |
| Immunofluorescence | Subcellular localization of LSU proteins | Nuclear vs cytosolic distribution |
| Polysome profiling | mRNA distribution across polysomes | Translation efficiency of specific transcripts |
Ribosome Profiling (Ribo-seq)
Ribo-seq provides a snapshot of translating ribosomes at codon resolution. It can be used to assess how changes in LSU components affect global translation and codon occupancy. For example, Ribo-seq in cells with SPATA5 mutations reveals defects in translation elongation. This method is essential for linking LSU function to specific mRNA translation.
Sucrose Gradient Ultracentrifugation
Sucrose gradient analysis separates ribosomal subunits, monosomes, and polysomes. It is used to monitor LSU assembly defects; knockout of assembly factors like SPATA5 leads to accumulation of pre-60S particles. This technique is a classic method for studying ribosome biogenesis.
Cryo-Electron Microscopy
Cryo-EM resolves the structure of the LSU at near-atomic resolution, revealing the arrangement of rRNA and proteins. It has been used to determine the structure of the SPATA5 complex bound to pre-60S particles. Cryo-EM is also valuable for visualizing antibiotic binding to the LSU.
CRISPR Screens and Functional Genomics
Genome-wide CRISPR knockout screens can identify genes required for LSU function or resistance to drugs targeting the ribosome. For instance, screens with tigecycline can reveal modifiers of mitochondrial ribosome toxicity. These screens are powerful for discovering novel assembly factors and disease modifiers.
How CRISPR Can Be Used to Study GO:0022625 cytosolic large ribosomal subunit
Knockout
CRISPR knockout of genes encoding LSU proteins or assembly factors is used to study their essentiality and function. For example, knockout of SPATA5 in human cells leads to defective pre-60S maturation and impaired translation. Knockout models are valuable for dissecting the role of individual LSU components in ribosome biogenesis and disease.
Point Mutation
CRISPR point mutation knock-in allows the introduction of specific disease-associated mutations. For instance, mutations in the Fe-S cluster of Mak16 can be modeled to study its role in LSU assembly. Point mutations in RPL5 found in Diamond-Blackfan anemia can be knocked into cell lines to study their effects on ribosome function.
Knock-in
Tagged knock-in of LSU proteins or assembly factors enables visualization and purification. For example, knock-in of GFP-tagged SPATA5 allows tracking of pre-60S particles. Knock-in of epitope tags on OPENER subunits facilitates immunoprecipitation and localization studies in plants.
Overexpression
CRISPR activation (CRISPRa) or cDNA overexpression can be used to overexpress LSU proteins. Overexpression of RPLP1 in cancer cells promotes translation and proliferation. Such models are useful for studying the oncogenic potential of LSU components and for drug screening.
How EDITGENE Supports cytosolic large ribosomal subunit Research
Researchers studying cytosolic large ribosomal subunit-related genes often need to determine whether a candidate gene is causally involved in ribosome biogenesis, translation, or disease. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models, enabling functional validation and mechanistic studies.
Contact EDITGENE today to design your custom CRISPR model for cytosolic large ribosomal subunit research.
Frequently Asked Questions About cytosolic large ribosomal subunit
What is the cytosolic large ribosomal subunit?
The cytosolic large ribosomal subunit (GO:0022625) is the larger of the two ribosomal subunits located in the cytosol. It catalyzes peptide bond formation during protein synthesis and is known as the 60S subunit in eukaryotes and the 50S subunit in prokaryotes.
What genes are involved in the cytosolic large ribosomal subunit?
Key genes include RPL3, RPL4, RPL5, RPL11, RPLP0, RPLP1, RPLP2, and assembly factors such as SPATA5 and MAK16.
What is the function of the 60S ribosomal subunit?
The 60S subunit, or cytosolic large ribosomal subunit, catalyzes peptide bond formation and forms the exit tunnel for nascent polypeptides. It also interacts with translation factors during elongation.
How is the cytosolic large ribosomal subunit assembled?
Assembly involves processing of rRNA, sequential binding of ribosomal proteins, and the action of transient assembly factors like SPATA5. It occurs in the nucleus and is completed in the cytosol.
What diseases are associated with cytosolic large ribosomal subunit defects?
Defects cause ribosomopathies such as Diamond-Blackfan anemia, Shwachman-Diamond syndrome, and neurodevelopmental disorders like SPATA5-related epilepsy.
What is the difference between cytosolic and mitochondrial large ribosomal subunits?
The cytosolic LSU (60S) translates nuclear-encoded mRNAs, while the mitochondrial LSU (39S) translates mitochondrial-encoded mRNAs. They have distinct protein compositions and antibiotic sensitivities.
How can I study the cytosolic large ribosomal subunit in the lab?
Common methods include sucrose gradient ultracentrifugation, Ribo-seq, cryo-EM, and CRISPR knockout screens.
What is the role of SPATA5 in the cytosolic large ribosomal subunit?
SPATA5 is an AAA+ ATPase that drives late pre-60S maturation. Mutations in SPATA5 cause epilepsy, hearing loss, and developmental delay.
What are ribosomal RNA expansion segments?
Expansion segments are variable regions in rRNA that fine-tune translation and provide binding sites for regulatory factors. They are features of the cytosolic large ribosomal subunit.
Can CRISPR be used to model ribosomopathies?
Yes, CRISPR knockout or point mutation knock-in of LSU genes in cell lines or iPSCs can model ribosomopathies and help identify therapeutic targets.
Conclusion
The cytosolic large ribosomal subunit (GO:0022625) is a central component of the translation machinery, essential for protein synthesis and cellular homeostasis. Its assembly is a complex process requiring numerous assembly factors, and its dysfunction is linked to a spectrum of human diseases, from ribosomopathies to cancer. Advances in CRISPR-based genome editing and structural biology have provided powerful tools to dissect LSU biology. EDITGENE offers comprehensive services to support researchers in generating precise cell models and conducting functional screens, accelerating discoveries in ribosome biology and therapeutic development.
References
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