How do spliceosomes affect gene expression?

In the cell nucleus, pre-mRNA splicing is carried out by the spliceosome. The spliceosome is responsible for accurately removing introns from pre-mRNA transcripts and joining together the remaining exons to form mature mRNA molecules. High-throughput sequencing studies have shown that around 95% of human genes undergo alternative splicing, allowing for the generation of multiple mRNA variants from a single DNA gene. This alternative splicing results in the production of multiple protein isoforms or the inclusion of diverse regulatory sequences in untranslated regions. This results in a significant increase in biological diversity. Controlling this process influences when and where specific protein variants are made, allowing alterations in alternative splicing to impact numerous cellular functions. As a result, pre-mRNA splicing needs to happen accurately and precisely to ensure the correct production of functional mRNA molecules. The spliceosome's structure and components can change, allowing it to be both precise and adaptable in its functions. Splicing also plays a role in placing proteins such as the exon junction complex (EJC) onto exons. This can affect where mRNA is located within cells, how quickly it is broken down, and how efficiently it is translated into proteins. The location of the EJC relative to the stop codon plays an essential role in determining cellular protein abundance through mRNA decay pathways.