I 14.11 The splicing of nuclear introns requires a two-step process. First, cleavage takes place at the 5' splice site, and a lariat is formed by the attachment of the 5' end of the intron to the branch point. Second, cleavage takes place at the 3' splice site, and two exons are spliced together.

The spliced mRNA is exported to the cytoplasm and translated.

Table 14.2 RNA-RNA interactions in pre-mRNA splicing

Exon 1


U1 with 5' splice site

U2 with branch point U2 with U6

U6 with 5' splice site U5 with 3' end of first exon

U5 with 3' end of one exon and 5' end of the other U4 with U6

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