Splicing of mRNA is the process by which the non-coding introns are removed from RNA transcripts, leaving only the part of the gene is translated into amino acids. In some cases, the RNA transcript can be spliced in more than one way to produce multiple mRNA transcripts.
Splicing primarily occurs in eukaryotic cells. Most bacterial genes are transcribed and entirely translated into protein, but eukaryotic cells require a wider range of protein products. There is more than one pathway for mRNA splicing. The different pathways are chosen depending on the type of intron that needs to be spliced out of the mRNA.
The most common type of mRNA splicing requires a large RNA and protein complex called the spliceosome. The small RNA molecules in the spliceosome interact directly with the mRNA and may even act as catalysts. Most of the splices carried out by the spliceosome have the same bases at the edges of the splice site. For example, the 5' site will contain the sequence GU, and the 3' site will contain AG.
Self-splicing mRNA is mRNA that does not require the help of a spliceosome to carry out the biochemical steps necessary to remove the intron from the mRNA.