Spliceosome

Spliceosome

The Spliceosome is a large and complex molecular machine found primarily within the nucleus of eukaryotic cells. The spliceosome is assembled from small nuclear RNAs (snRNA) and approximately 80 proteins. The role of the spliceosome is to remove introns from a transcribed pre-mRNA segment. This process is generally referred to as splicing.

Structure

The spliceosome consists of five small nuclear RNAs (snRNA) and a range of associated protein factors. When these components are combined, they form an active spliceosome. The snRNAs that make up the spliceosome are named U1, U2, U4, U5, and U6, and participate in several RNA-RNA and RNA-protein interactions. The RNA components of the spliceosome are rich in uridine.

Function

The primary function of the spliceosome is to remove introns from the pre-mRNA. This is a critical aspect of gene expression in eukaryotes. The spliceosome performs this function in a process called splicing. During splicing, the spliceosome catalyzes the excision of introns and the joining of exons.

Mechanism

The splicing process by the spliceosome involves the assembly of several subunits on the pre-mRNA substrate. The first step in the splicing process is the recognition and binding of the splice sites. The spliceosome then brings the exons close together and catalyzes the cutting and joining reactions.

Clinical significance

Defects in the splicing process, and thus in the spliceosome, can lead to numerous diseases, including cancer and various genetic disorders. Therefore, the spliceosome is a target of intense research in the field of medical science.

See also

• Alternative splicing
• Minor spliceosome
• Self-splicing intron
• Splice site mutation
• Splice site consensus sequence

References

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