mRNA Splicing -- Movie Narrative (Advanced Look)

The following animation will describe the process of RNA splicing--an important step in creating the mRNA that is involved in protein synthesis, via the process of translation. Key factors in this process include: RNA, possessing introns and exons, and the spliceosome.

Here we see an RNA molecule with a single intron. Several signals exist within the intron that are used in the splicing process. From the 5' end of the intron, these are, GU, the A branch site, a pyrimidine-rich region, and the 3' AG. The AG and GU sequences define the beginning and end of the intron.

Splicing is mediated by the spliceosome, which consists of several protein-RNA complexes. The first step involves two complexes that bind near the GU sequence. The RNA in then looped, and three other protein-RNA complexes bind. This final complex then undergoes a conformation change.

Introns are non-coding RNA sequences that must be removed before translation. The process of removing the intron is called splicing. The intron is then cleaved at the 5' GU sequence and forms a lariat at the A branch site. The 3' end of the intron is next cleaved at the AG sequence, and the two exons are ligated together.

As the spliced mRNA is released from the spliceosome, the intron debranches, and is then degraded.