Donor splice site (5' splice site (or 5ʹss))

The donor splice site, also known as the 5' splice site or 5ʹss, is a conserved nucleotide sequence at the exon-intron junction in pre-mRNA, typically beginning with the dinucleotide GT (GU in RNA), that marks the 5' end of an intron for recognition by the spliceosome.[1][3][5] During RNA splicing, U1 snRNP first binds this site to initiate spliceosome assembly, followed by recruitment of other components like U2 snRNP to the branch point and acceptor site, enabling two transesterification reactions that excise the intron and ligates exons.[1][3] Splicing kinetics at the donor site vary by sequence strength, intron length, and nucleotide composition, with optimal consensus sequences promoting faster cleavage and higher efficiency.[1][2] Mutations disrupting this site, such as changes to the GT dinucleotide, frequently cause aberrant splicing, leading to intron retention, exon skipping, or inclusion of intronic sequences, which produce dysfunctional proteins.[2][7][12] These variants are implicated in various genetic disorders and contribute to disease pathology, including cancer, by altering gene expression and protein function, though they are not directly targeted by approved therapeutics.[2][7][12]

Other names

5' splice site5ʹssdonor siteGT site5'-splice sitesplice donor site