U2-type spliceosomal complex

Definition

Target type: cellularcomponent

Any spliceosomal complex that forms during the splicing of a messenger RNA primary transcript to excise an intron that has canonical consensus sequences near the 5' and 3' ends. [GOC:krc, GOC:mah, PMID:11343900]

The U2-type spliceosomal complex is a large and intricate molecular machine that plays a crucial role in pre-mRNA splicing, a fundamental process in gene expression. It is responsible for recognizing and cleaving introns, the non-coding regions within a gene, and ligating the exons, the coding regions, together to generate mature mRNA. The complex is assembled from a variety of components, including:

* **snRNAs (small nuclear RNAs):** These are small RNA molecules that are essential for the catalytic activity of the spliceosome. The U2 snRNA, along with its associated proteins, is a key component of the U2 snRNP (small nuclear ribonucleoprotein). It recognizes the branch point sequence within the intron and forms a base pairing interaction with it, facilitating the first step of splicing.
* **snRNPs (small nuclear ribonucleoproteins):** These are protein-RNA complexes that are involved in various aspects of spliceosome assembly and function. The U2 snRNP, along with the U1, U4, U5, and U6 snRNPs, come together to form the mature spliceosome.
* **Non-snRNP proteins:** In addition to snRNPs, several non-snRNP proteins are involved in spliceosome assembly, function, and regulation. These proteins include splicing factors, which interact with the snRNPs and pre-mRNA to modulate splicing efficiency and specificity, and helicase proteins, which unwind RNA structures to facilitate splicing.

The U2 snRNP, a core component of the U2-type spliceosomal complex, is composed of the U2 snRNA and a set of associated proteins, including:

* **SF3A1 and SF3A3:** These proteins bind to the U2 snRNA and are essential for its proper folding and stability. They also interact with the branch point sequence within the intron, helping to recruit the U2 snRNP to the pre-mRNA.
* **SF3B1, SF3B2, and SF3B4:** These proteins are responsible for the assembly and integrity of the U2 snRNP complex. They interact with the U2 snRNA and other snRNPs to facilitate spliceosome formation.
* **SF3B3 and SF3B5:** These proteins are involved in the recognition and binding of the branch point sequence within the intron. They interact with the U2 snRNA and the pre-mRNA to ensure accurate splice site selection.

Together, these snRNPs and non-snRNP proteins assemble into a complex that recognizes the intron-exon boundaries, cleaves the intron, and ligates the exons. The process of splicing is highly regulated, and the composition and function of the U2-type spliceosomal complex can be influenced by various factors, including developmental stage, cell type, and environmental cues. This intricate regulatory network ensures that the correct exons are joined together to generate functional mRNA molecules.
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Proteins (1)

Compounds (4)