Acceptor splice site (3' splice site (or 3′ss))

The **acceptor splice site** is a conserved nucleotide sequence at the 3' end of an intron, typically featuring the dinucleotide AG, that marks the boundary between the intron and the downstream exon in pre-mRNA. It is recognized by the spliceosome, a complex of snRNPs and proteins including U2AF and U2 snRNP, which bind upstream elements like the branch point and polypyrimidine tract to facilitate precise intron excision and exon joining during splicing. The site is essential for accurate mRNA maturation, with the spliceosome scanning from the branch point to select the first suitable AG, influencing splicing efficiency and isoform production. Mutations or variants creating ectopic AG dinucleotides nearby can activate cryptic sites, leading to aberrant splicing such as exon skipping, intron retention, or frameshifts, which disrupt protein function. These disruptions are implicated in diseases like cancer and genetic disorders, where splice site variants alter gene expression and contribute to pathology, though the site itself is not a protein-based therapeutic target. Non-canonical acceptor sites exist but are rare, handled by minor spliceosomes. Overall, the acceptor splice site ensures proteomic diversity through alternative splicing while maintaining splicing fidelity.

Other names

3' splice site3′ssacceptor site