Spleiß

Spleiß, in biology often translated as splicing, is the RNA processing step by which introns are removed from a precursor messenger RNA (pre-mRNA) and the remaining exons are joined to form a mature messenger RNA that can be translated into a protein. In German scientific usage, Spleiß denotes this essential modification of transcripts in many eukaryotes.

The most well-characterized pathway is pre-mRNA splicing mediated by the spliceosome, a dynamic complex composed of small nuclear ribonucleoproteins (snRNPs) and numerous proteins. The process begins with recognition of the 5' splice site, the branch point, and the 3' splice site. Through a series of rearrangements and two sequential transesterification reactions, the intron is excised as a lariat structure and the exons are ligated to produce a continuous coding sequence.

Splicing is tightly regulated and contributes to gene expression diversity through alternative splicing, in which different combinations of exons are joined to generate multiple mRNA isoforms from a single gene. This regulation involves cis-regulatory elements in the RNA, such as exonic and intronic splicing enhancers and silencers, and trans-acting factors including SR proteins and heterogeneous nuclear ribonucleoproteins (hnRNPs).

Beyond the canonical spliceosome pathway, some organisms and organelles employ self-splicing introns (group II and certain bacteria-like systems) that can catalyze splicing without the full protein machinery. Mis-splicing or aberrant regulation can lead to disease, and targeted therapies are being developed to modulate splicing patterns in various conditions. Spleiß thus plays a central role in gene expression and cellular function.