Processing of pro-mRNA (mRNA maturation) includes the processes of splicing, capping of the 5th end of RNA, removal of nucleotides at the 3rd end, and the formation of a polyadenine tail.
To start the translation process, a transcript must be created. An exon is semantic, an intron is non-semantic; it needs to be cut out. It is possible to cut pro-mRNA using enzymes to further remove introns. These compounds have a specific sequence that recognizes their enzyme. This means that there are only short exons. The stitching process is called splicing. There are special processes that accelerate (enhancers) or slow down (silencers) these processes.
The next step, capping of the anterior mRNA, is the addition of 7-methyl-guanosine to the 5'-end. It does not allow enzymes capable of cutting RNA, this allows you to export RNA from the nucleus to the cytoplasm and provide binding of RNA to the ribosome.
The next stage is polyadenylation (takes place in 2 stages): stage 1 - 20 nucleotides are deleted at the 3'-end of the pro-mRNA to the site of polyadenylation initiation. Stage 2 - adenine bases are attached to the 3'-end, a polyadenine tail is formed that protects the mRNA.