Spliceosome

The team at the CRG altered the expression of 305 spliceosome-related genes in human cancer cells one by one, observing the effects on splicing across the entire genome.

Another theory is that the spliceosome and the intron-exon structure of genes is a relic of the RNA world (the introns-first hypothesis). citation There is still considerable debate about the extent to which of these hypotheses is most correct.

Assembly and activity of the spliceosome occurs during transcription of the pre-mRNA.

First, the 2'OH of a specific branchpoint nucleotide within the intron, defined during spliceosome assembly, performs a nucleophilic attack on the first nucleotide of the intron at the 5' splice site, forming the lariat intermediate.

Group I and II introns perform splicing similar to the spliceosome without requiring any protein.

This similarity suggests that Group I and II introns may be evolutionarily related to the spliceosome.

When recognized by the spliceosome, the sequence between the original and duplicated AGGT will be spliced, resulting in the creation of an intron without alteration of the coding sequence of the gene.