A splice donor site, also known as a 5' splice site, is a specific sequence of nucleotides located at the beginning or upstream of an exon in a pre-mRNA molecule. It is a crucial component involved in the process of RNA splicing, which is a fundamental step in gene expression.
During RNA splicing, the splice donor site plays a pivotal role in determining the precise location where the introns, non-coding regions within pre-mRNA, are removed and the exons, coding regions, are joined together. This site is recognized by spliceosomal machinery, which is a complex composed of small nuclear ribonucleoproteins (snRNPs) and other proteins.
Typically, the splice donor site consists of a highly conserved consensus sequence found in eukaryotes, which consists of a short motif, usually "GU" dinucleotide, followed by a stretch of nucleotides that vary among different genes. The "GU" dinucleotide serves as a critical recognition signal for the spliceosome and marks the starting point of intron removal.
Mutations or alterations in the splice donor site sequence can have a significant impact on RNA splicing efficiency and accuracy. Changes in this site can result in aberrant splicing patterns, causing diseases such as genetic disorders, cancers, or other conditions associated with protein malfunction. Therefore, the characterization and understanding of splice donor sites play a vital role in elucidating gene regulation mechanisms and identifying potential therapeutic targets.
