GO:0071011 precatalytic spliceosome: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0071011 (precatalytic spliceosome) is a cellular_component term describing the spliceosomal complex formed when a preassembled U5-containing tri-snRNP is recruited to the prespliceosome.
• Although all five small nuclear ribonucleoproteins (snRNPs) are present, the precatalytic spliceosome is catalytically inactive and must undergo activation before the first transesterification step of pre-mRNA splicing.
• The complex is also known as mammalian spliceosomal complex B or B1, and yeast spliceosomal complex A2-1, reflecting its conservation across eukaryotes.
• Key regulatory events at this stage include phosphorylation of SF3B1 by CDK11, which controls pre-mRNA splicing progression.
• The RES complex is required for efficient transformation of the precatalytic B spliceosome into the activated B(act) complex.
• Structural and biochemical studies of the precatalytic spliceosome provide a framework for understanding splicing fidelity and its links to human disease.
Description
The precatalytic spliceosome (GO:0071011) is a cellular_component defined as a spliceosomal complex formed by the recruitment of a preassembled U5-containing tri-snRNP to the prespliceosome. At this stage, all five snRNPs are present, but the complex remains catalytically inactive, representing a critical checkpoint before the spliceosome is activated for catalysis. Understanding this complex is essential because it sits at the transition between spliceosome assembly and the catalytic steps of pre-mRNA splicing, a process that shapes the coding potential of most human genes. Researchers study the precatalytic spliceosome to dissect how splicing fidelity is achieved and how regulatory inputs, such as phosphorylation, control the timing of activation. The complex includes many proteins in addition to the snRNP components, and its composition has been resolved by structural and biochemical approaches. Because defects in spliceosome assembly and function are linked to diseases including cancer and neurodegeneration, the precatalytic spliceosome is a focal point for mechanistic and translational studies. This article integrates the QuickGO definition with verified PubMed literature to describe the structure, composition, regulation, and research methods relevant to GO:0071011. It is intended for scientists who need a precise, citation-backed overview of the precatalytic spliceosome and its role in gene expression.
precatalytic spliceosome At A Glance
| GO ID | GO:0071011 |
|---|---|
| GO term | precatalytic spliceosome |
| Ontology | cellular_component |
| Synonym | mammalian spliceosomal complex B; mammalian spliceosomal complex B1; yeast spliceosomal complex A2-1 |
| Major function | Serves as a catalytically inactive spliceosomal intermediate formed by tri-snRNP recruitment to the prespliceosome, poised for activation |
| Composition | Contains all five snRNPs plus many additional proteins |
| Assembly stage | Formed after prespliceosome assembly and before catalytic activation |
| Conservation | Detected in mammalian and yeast systems, with conserved core components |
What Is GO:0071011?
The precatalytic spliceosome is a spliceosomal complex that forms when a preassembled U5-containing tri-snRNP is recruited to the prespliceosome. It contains all five snRNPs but is catalytically inactive, meaning it cannot yet perform the transesterification reactions of pre-mRNA splicing. The complex includes numerous proteins beyond those found in the associated snRNPs, and it is also referred to as mammalian spliceosomal complex B or B1, and yeast spliceosomal complex A2-1.
Why Is precatalytic spliceosome Important in Cell Biology?
The precatalytic spliceosome is important because it represents a key regulatory checkpoint in pre-mRNA splicing, where the spliceosome is fully assembled but not yet catalytically active. This stage ensures that splicing occurs with high fidelity and that activation is properly timed, processes that are influenced by phosphorylation events such as CDK11-mediated phosphorylation of SF3B1. Defects in spliceosome assembly or regulation can alter gene expression programs and have been linked to human diseases, making the precatalytic spliceosome a relevant target for mechanistic and translational research.
• Defines a conserved intermediate in spliceosome assembly that is essential for accurate pre-mRNA splicing.
• Provides a checkpoint for quality control before catalytic activation of the spliceosome.
• Is regulated by phosphorylation events, including CDK11-dependent phosphorylation of SF3B1.
• Requires the RES complex for efficient transition to the activated B(act) complex.
• Contains RBM5 and RBM10, splicing regulators that engage intron branch sites on chromatin.
• Serves as a structural model for understanding human spliceosome activation.
• Is relevant to cancer biology because spliceosome components are frequently altered in tumors.
• Can be studied using knockout, point-mutation, and knock-in cell models to dissect component functions.
• Offers opportunities for CRISPR library screening to identify regulators of spliceosome activation.
• Supports the development of bioinformatics pipelines for analyzing splicing changes in disease.
What Happens During precatalytic spliceosome?
Recruitment of the tri-snRNP to the prespliceosome
In simple terms: The cell adds a preassembled U5-containing tri-snRNP to an earlier spliceosome complex, creating the precatalytic spliceosome.
The precatalytic spliceosome is formed when a preassembled U5-containing tri-snRNP is recruited to the prespliceosome. This recruitment brings all five snRNPs together, but the complex remains catalytically inactive. Structural studies have visualized this assembly step, revealing how the tri-snRNP docks onto the prespliceosome.
Composition and inactive state
In simple terms: Even though all the small nuclear RNAs are present, the spliceosome cannot cut RNA yet.
Although all five snRNPs are present in the precatalytic spliceosome, the complex is catalytically inactive. It includes many proteins in addition to those found in the associated snRNPs, and its composition has been analyzed by biochemical and structural methods. The inactive state is maintained until specific activation signals trigger rearrangement.
Transition to the activated B(act) complex
In simple terms: The precatalytic spliceosome must be remodeled into an active form before it can perform splicing.
The RES complex is required for efficient transformation of the precatalytic B spliceosome into an activated B(act) complex. This transition involves structural rearrangements and is a prerequisite for catalysis. Cwc25 also plays a central role in spliceosome dynamics during the catalytic phase, linking the precatalytic stage to later steps.
Regulation by phosphorylation
In simple terms: Chemical tags called phosphates are added to spliceosome proteins to control when splicing proceeds.
CDK11 regulates pre-mRNA splicing by phosphorylation of SF3B1, a component of the spliceosome. This phosphorylation event influences the progression from the precatalytic state to activation. Such regulatory modifications help coordinate splicing with cellular signals.
Structural insights into the precatalytic spliceosome
In simple terms: Scientists have taken detailed pictures of this complex to see how its parts fit together.
Structures of a pre-catalytic spliceosome have been determined, providing a framework for understanding its architecture. Structural insights into human exon-defined spliceosome prior to activation have further clarified the organization of this complex. Molecular basis for the activation of human spliceosome has also been described, linking structure to function.
Key Genes Involved in GO:0071011 precatalytic spliceosome
The following genes and proteins are key components or regulators of the precatalytic spliceosome, based on verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SF3B1 | Spliceosome component phosphorylated by CDK11; involved in splicing regulation | Target for studying phosphorylation-dependent splicing control |
| CDK11 | Kinase that phosphorylates SF3B1 to regulate pre-mRNA splicing | Potential therapeutic target in splicing-related diseases |
| RBM5 | Splicing regulator and U2 snRNP subunit engaged with intron branch sites | Implicated in splicing fidelity and cancer biology |
| RBM10 | Splicing regulator and U2 snRNP subunit engaged with intron branch sites | Associated with splicing regulation and disease |
| Cwc25 | Central role in spliceosome dynamics during catalytic phase | Model for studying transition from precatalytic to catalytic states |
| RES complex components | Required for efficient transformation of precatalytic B to B(act) | Targets for understanding spliceosome activation |
| U5 snRNP proteins | Part of the tri-snRNP recruited to form the precatalytic spliceosome | Structural and functional studies of assembly |
| U2 snRNP proteins | Present in the prespliceosome and precatalytic complex | Study of branch site recognition |
| U1 snRNP proteins | Component of the prespliceosome before tri-snRNP recruitment | Assembly intermediate analysis |
| U4/U6 snRNP proteins | Part of the tri-snRNP that joins the prespliceosome | Role in precatalytic complex formation |
| SF3A1 | U2 snRNP component involved in spliceosome assembly | Research on spliceosome composition |
| SF3B2 | U2 snRNP component and splicing factor | Studies of phosphorylation and regulation |
| Prp proteins (yeast) | Conserved splicing factors in precatalytic complex | Yeast models for spliceosome assembly |
| Spliceosomal ATPases | Drive rearrangements during activation | Targets for understanding energy-dependent steps |
| Exon junction complex proteins | Deposited during splicing, linked to precatalytic stage | Research on splicing-coupled mRNA packaging |
| SR proteins | Splicing regulators that influence assembly | Study of regulatory networks |
| hnRNP proteins | RNA-binding proteins affecting spliceosome assembly | Investigation of splicing regulation |
How Is precatalytic spliceosome Regulated?
The precatalytic spliceosome is regulated by phosphorylation events, notably CDK11-mediated phosphorylation of SF3B1, which controls pre-mRNA splicing progression. The RES complex is required for efficient transformation of the precatalytic B spliceosome into the activated B(act) complex, providing a regulatory checkpoint. Additionally, splicing regulators such as RBM5 and RBM10 are subunits of the U2 snRNP engaged with intron branch sites on chromatin, influencing assembly and activation. These regulatory mechanisms ensure that splicing occurs accurately and in response to cellular signals.
precatalytic spliceosome and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SF3B1 | Cancer, splicing dysregulation | Knockout or point-mutation cell lines |
| RBM5 | Cancer, splicing regulation | Knockout and overexpression models |
| RBM10 | Cancer, splicing regulation | Knockout and overexpression models |
| CDK11 | Cancer, splicing control | Point-mutation and knockout models |
| RES complex components | Splicing-related disorders | Knockout models in yeast and mammalian cells |
Cancer
Alterations in spliceosome components, including SF3B1 and regulators such as RBM5 and RBM10, have been linked to cancer biology. The precatalytic spliceosome stage is critical for splicing fidelity, and its dysregulation can contribute to oncogenic gene expression programs.
Neurodegeneration
Defects in spliceosome assembly and function have been associated with neurodegenerative conditions, although specific mechanisms involving the precatalytic spliceosome require further study. Structural insights into human spliceosome activation provide a basis for understanding how mutations might affect this stage.
Developmental disorders
Because the precatalytic spliceosome is essential for pre-mRNA splicing, mutations in core components could disrupt development. Research using model systems has begun to elucidate how assembly defects impact organismal phenotypes.
From precatalytic spliceosome-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of SF3B1 affect precatalytic spliceosome assembly? | SF3B1 knockout cell line |
| How does CDK11 phosphorylation of SF3B1 regulate splicing? | CDK11 point-mutation knock-in |
| What is the role of RBM5 in branch site recognition? | RBM5 knockout and tagged knock-in |
| How does the RES complex promote B to B(act) transition? | RES component knockout |
| Can overexpression of Cwc25 alter spliceosome dynamics? | Cwc25 overexpression cell model |
| What proteins associate with the precatalytic spliceosome? | Tagged knock-in of core components followed by proteomics |
How to Study the precatalytic spliceosome Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Cryo-EM | Three-dimensional structure of spliceosomal complexes | Visualizing precatalytic spliceosome architecture |
| In vitro splicing assay | Splicing activity and complex transitions | Studying precatalytic to catalytic progression |
| Mass spectrometry | Protein composition of spliceosomal complexes | Identifying novel components |
| RNA-seq | Changes in splicing patterns | Assessing impact of spliceosome mutations |
| CRISPR knockout | Loss-of-function effects on splicing | Testing gene requirement in precatalytic stage |
| CRISPR point mutation | Effect of specific amino acid changes | Modeling disease-associated mutations |
| Tagged knock-in | Localization and interactions of proteins | Affinity purification of complexes |
| Bioinformatics | Prediction of splicing networks | Integrating structural and genomic data |
Structural biology (cryo-EM)
Cryo-electron microscopy has been used to determine the structure of a pre-catalytic spliceosome, revealing its architecture and component interactions. Structural insights into human exon-defined spliceosome prior to activation have also been obtained using similar approaches.
Biochemical assays
In vitro splicing assays and snRNA analysis have been used to study the precatalytic spliceosome and its transition to active states. These methods help define the composition and dynamics of the complex.
Proteomics and mass spectrometry
Mass spectrometry-based proteomics can identify proteins associated with the precatalytic spliceosome, including many non-snRNP factors. This approach is useful for mapping dynamic changes during assembly.
Genetic and CRISPR screens
CRISPR knockout and point-mutation models enable functional dissection of genes involved in precatalytic spliceosome regulation. Library screening can identify modifiers of splicing and spliceosome activation.
How CRISPR Can Be Used to Study GO:0071011 precatalytic spliceosome
Knockout
CRISPR knockout of genes encoding precatalytic spliceosome components, such as SF3B1 or RES complex subunits, can reveal their requirement for spliceosome assembly and cell viability. These models are useful for identifying essential factors and compensatory pathways.
Point Mutation
Point mutations in genes like SF3B1 can be introduced to mimic disease-associated variants and study their effects on precatalytic spliceosome function. Such models help dissect phosphorylation-dependent regulation.
Knock-in
Knock-in of tagged versions of core components, such as RBM5 or RBM10, enables affinity purification and localization studies of the precatalytic spliceosome. This approach facilitates proteomic and imaging analyses.
Overexpression
Overexpression of regulators like Cwc25 can be used to test gain-of-function effects on spliceosome dynamics and catalytic progression. These models complement loss-of-function studies.
How EDITGENE Supports precatalytic spliceosome Research
Researchers studying precatalytic spliceosome-related genes often need to determine whether a candidate gene is causally involved in spliceosome assembly, activation, or splicing fidelity. EDITGENE provides CRISPR-based cell models and screening services to enable such functional studies with high specificity and reproducibility.
Contact EDITGENE today to design your custom CRISPR model for precatalytic spliceosome research.
Frequently Asked Questions About precatalytic spliceosome
What is the precatalytic spliceosome?
The precatalytic spliceosome (GO:0071011) is a spliceosomal complex formed by recruitment of a preassembled U5-containing tri-snRNP to the prespliceosome; it contains all five snRNPs but is catalytically inactive.
What genes are involved in the precatalytic spliceosome?
Key genes include SF3B1, CDK11, RBM5, RBM10, Cwc25, and components of the RES complex, among others.
Why is the precatalytic spliceosome important?
It serves as a regulatory checkpoint before catalytic activation of the spliceosome, ensuring splicing fidelity and proper gene expression.
What is the difference between precatalytic and catalytic spliceosome?
The precatalytic spliceosome is catalytically inactive despite containing all five snRNPs, whereas the catalytic spliceosome has undergone activation and can perform the transesterification reactions of splicing.
How is the precatalytic spliceosome regulated?
It is regulated by phosphorylation events, such as CDK11-mediated phosphorylation of SF3B1, and by the RES complex, which promotes transition to the activated B(act) complex.
What diseases are linked to precatalytic spliceosome dysfunction?
Dysregulation of spliceosome components has been linked to cancer and neurodegeneration, though specific mechanisms continue to be investigated.
How can I study the precatalytic spliceosome in the lab?
Common methods include cryo-EM, in vitro splicing assays, mass spectrometry, RNA-seq, and CRISPR-based knockout or point-mutation models.
What is the role of SF3B1 in the precatalytic spliceosome?
SF3B1 is a spliceosome component that is phosphorylated by CDK11, which regulates pre-mRNA splicing progression.
What is the RES complex and how does it relate to the precatalytic spliceosome?
The RES complex is required for efficient transformation of the precatalytic B spliceosome into the activated B(act) complex.
Can CRISPR be used to study precatalytic spliceosome genes?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are widely used to dissect the functions of precatalytic spliceosome components.
Conclusion
The precatalytic spliceosome (GO:0071011) is a conserved, catalytically inactive spliceosomal complex that forms when the U5-containing tri-snRNP joins the prespliceosome. It serves as a critical checkpoint in pre-mRNA splicing, regulated by phosphorylation and the RES complex, and is composed of all five snRNPs plus numerous additional proteins. Understanding its structure and function provides insights into splicing fidelity and human disease. Researchers can leverage CRISPR-based knockout, point-mutation, knock-in, and overexpression models, along with structural and bioinformatics approaches, to investigate the precatalytic spliceosome. EDITGENE offers comprehensive services to support such studies, from custom cell line generation to library screening and data analysis.
References
- 1. Hluchý M et al.. 2022. CDK11 regulates pre-mRNA splicing by phosphorylation of SF3B1.. Nature 609(7928):829-834 PMID: 36104565
- 2. Zhan X et al.. 2024. Molecular basis for the activation of human spliceosome.. Nat Commun 15(1):6348 PMID: 39068178
- 3. Plaschka C et al.. 2017. Structure of a pre-catalytic spliceosome.. Nature 546(7660):617-621 PMID: 28530653
- 4. Damianov A et al.. 2024. The splicing regulators RBM5 and RBM10 are subunits of the U2 snRNP engaged with intron branch sites on chromatin.. Mol Cell 84(8):1496-1511.e7 PMID: 38537639
- 5. Yean SL et al.. 1996. Analysis of small nuclear RNAs in a precatalytic spliceosome.. Gene Expr 5(6):301-13 PMID: 8836738
- 6. Bao P et al.. 2017. The RES complex is required for efficient transformation of the precatalytic B spliceosome into an activated B(act) complex.. Genes Dev 31(23-24):2416-2429 PMID: 29330354
- 7. Zhang W et al.. 2024. Structural insights into human exon-defined spliceosome prior to activation.. Cell Res 34(6):428-439 PMID: 38658629
- 8. Tseng CK et al.. 2017. A central role of Cwc25 in spliceosome dynamics during the catalytic phase of pre-mRNA splicing.. RNA 23(4):546-556 PMID: 28057857
