GO:1903241 U2-type prespliceosome assembly: Genes & Methods

U2-type prespliceosome assembly (GO:1903241) is the biological process in which a set of spliceosomal components aggregates, arranges, and bonds together to form the U2-type prespliceosome, also known as the major prespliceosome or mammalian spliceosomal complex A. This assembly is an early and essential step in the splicing of GT-AG introns, the most common class of introns in human pre-mRNAs. The prespliceosome is a dynamic ribonucleoprotein complex that commits the spliceosome to the major U2-dependent splicing pathway, distinguishing it from the minor U12-type pathway. Understanding this process is fundamental to deciphering how genetic information is processed and how splicing errors contribute to disease. The U2-type prespliceosome is built on a pre-mRNA substrate through the coordinated action of small nuclear ribonucleoproteins (snRNPs) and numerous auxiliary proteins. The U1 snRNP first recognizes the 5' splice site, and the U2 snRNP subsequently engages the branch point sequence, leading to the stable prespliceosome. This step is ATP-dependent and involves multiple conformational rearrangements. The assembly is highly regulated to ensure splicing fidelity, and its disruption can lead to widespread changes in gene expression. Researchers study U2-type prespliceosome assembly to understand basic RNA processing, to identify targets for therapeutic intervention in splicing-related diseases, and to develop tools for manipulating gene expression. The process is also a paradigm for studying dynamic ribonucleoprotein complex assembly and RNA-protein interactions. This article provides a comprehensive overview of the definition, mechanism, key genes, disease links, and research methods for GO:1903241, with a focus on CRISPR-based approaches for functional genomics.

According to the Gene Ontology, GO:1903241 (U2-type prespliceosome assembly) is defined as the aggregation, arrangement and bonding together of a set of components to form an U2-type prespliceosome. In other words, it is the stepwise assembly of the major prespliceosome, a spliceosomal complex that forms on pre-mRNA before the catalytic steps of splicing. This process is also known by synonyms such as GT-AG prespliceosome assembly, major prespliceosome formation, and mammalian U2-type spliceosomal complex A assembly. It is a biological process that occurs in the nucleus and is essential for the removal of GT-AG introns from pre-mRNA.

U2-type prespliceosome assembly is a central step in pre-mRNA splicing, a process that affects nearly all human genes. Accurate assembly ensures correct intron recognition and removal, which is vital for producing functional proteins. Dysregulation of prespliceosome assembly can cause widespread splicing defects, leading to diseases such as cancer, neurodegeneration, and developmental disorders. Moreover, many pathogens and viruses hijack the splicing machinery, making this process a potential therapeutic target. Studying GO:1903241 provides insights into fundamental RNA biology and offers opportunities for therapeutic intervention.

The following genes encode core and accessory components of the U2-type prespliceosome assembly machinery, with established roles in splicing and disease.

U2-type prespliceosome assembly is regulated at multiple levels. Post-translational modifications of splicing factors, such as phosphorylation of SR proteins by SRPK and CLK kinases, control their activity and localization. ATP-dependent RNA helicases, including Prp5 and Sub2, provide proofreading and energy for conformational changes. Additionally, the assembly is coupled to transcription and influenced by chromatin structure and RNA polymerase II elongation rate. Signaling pathways such as the mTOR pathway can indirectly affect splicing by regulating the expression of splicing factors. In the minor spliceosome, proteins like U11-48K and U11-59K modulate 5' splice site recognition, highlighting evolutionary conservation of regulatory mechanisms.

Mutations in core prespliceosome components, particularly SF3B1, are frequent in myelodysplastic syndromes (MDS), chronic lymphocytic leukemia (CLL), and uveal melanoma. These mutations alter branch point recognition and lead to aberrant splicing of key genes, promoting oncogenesis. U2AF1 mutations are also found in MDS and lung adenocarcinoma. Targeting the prespliceosome with splicing modulators is a promising therapeutic strategy.

Dysregulation of prespliceosome assembly contributes to neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). For example, TDP-43 pathology is associated with altered splicing of prespliceosome components. Mutations in splicing factors like RBM10 have been linked to neurodegeneration.

Mutations in PRPF8, PRPF31, and other spliceosomal proteins cause retinitis pigmentosa, a common inherited retinal dystrophy. These mutations impair prespliceosome assembly and lead to photoreceptor cell death. The exact mechanisms are under investigation using model organisms and patient-derived cells.

Mutations in SNRPB cause cerebrocostomandibular syndrome, a rare developmental disorder characterized by craniofacial and rib anomalies. This highlights the importance of prespliceosome assembly in embryonic development. Other splicing factors are implicated in neurodevelopmental disorders.

RNA-seq and RT-PCR are used to measure splicing changes upon perturbation of prespliceosome assembly. CLIP-seq and RIP-seq can map RNA-protein interactions of splicing factors. These methods reveal global splicing defects and alternative splicing events.

Affinity purification coupled with mass spectrometry (AP-MS) identifies protein-protein interactions within the prespliceosome. Proximity labeling (BioID, APEX) can capture transient interactions in living cells. These approaches define the composition and dynamics of the complex.

Fluorescence microscopy and live-cell imaging visualize the assembly of fluorescently tagged snRNPs. Cryo-electron microscopy (cryo-EM) provides high-resolution structures of the prespliceosome. These techniques reveal conformational changes during assembly.

CRISPR knockout screens and RNAi screens identify genes required for prespliceosome assembly. Reporter assays with minigenes detect splicing efficiency. These methods enable systematic discovery of assembly factors.

Researchers studying U2-type prespliceosome assembly-related genes often need to determine whether a candidate gene is causally involved in splicing regulation, disease pathogenesis, or drug response. EDITGENE provides comprehensive CRISPR-based services to generate precisely engineered cell models, enabling functional validation and mechanistic studies.

U2-type prespliceosome assembly (GO:1903241) is a fundamental biological process that ensures accurate pre-mRNA splicing of GT-AG introns. Its dysregulation is implicated in a wide range of human diseases, from cancer to neurodegeneration. Understanding the molecular mechanisms and key genes involved provides opportunities for therapeutic intervention. CRISPR-based models are powerful tools for dissecting this process and validating drug targets. EDITGENE offers comprehensive services to support your research in this field.