Spliceosome
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A spliceosome is a complex of RNA and many protein subunits called snRNP's, that removes the non-coding introns from unprocessed mRNA. Spliceosomes are unique to eukaryotic mRNA as the mRNA of prokaryotes lack introns. The snRNP's 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 part is rich in uridine (the U nucleotides). There are specific 5' and 3' sites on the pre-mRNA that the spliceosome recognises. The nucleotide sequence between these locations is removed, and the two exons are spliced together. In accordance with the GU-AG rule, all introns have a 5' GU and a 3' AG recognition sequence which the spliceosome recognizes and excises as a lariat whereby the sequence is subsequently destroyed.
A group of less abundant snRNPs, U11, U12, U4atac, and U6atac, together with U5, are subunits of the so-called minor spliceosome that splices a rare class of pre-mRNA introns, denoted U12-type.
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[edit] Alternative splicing
Alternative splicing (the re-combination of different exons) is a major source of genetic diversity in eukaryotes. Splice variants have been used to account for the relatively small number of genes in the human genome. For years the estimate widely varied with top estimates reaching 100,000 genes[reference required], but now, thanks to the Human Genome Project we know the figure is closer to 30,000 genes. However, almost every human gene is thought to have at least two isoforms[reference required].
[edit] Spliceome
The term spliceome was coined in the early 21st century to describe the set of all possible alternative splices in an organism. It is an analogy to the genome or proteome. The concept and list of alternative splices is useful in bioinformatics and computational biology. It allows modular development of computational technology to deal with the spliceome.
[edit] References
- Chapter 12, pp 311 7th ed, Vishal.
- Alberts, Bruce. Bray, Dennis. Hookin, Karen. Johnson, Alexander, Lewis, Julian, Raff, Martin, Roberts, Keith. Walter, Peter. essential cell biology Second edition, GS Garland Science, Taylor & Francis Group, NEW YORK AND LONDON.
