(1) "Cap" at the 5' end
The 5' end of mature mRNA in eukaryotic cells has a special structure, namely m7Gpp-pmnNp, which is called a "cap" . The production of cap is carried out in the nucleus, but there is also an enzyme system in the cytoplasm. The capping process of animal virus mRNA is carried out in the cytoplasm of the host cell.
(2) Add a "tail" to the 3' end
There is a conserved sequence at the 3' end of the mRNA precursor molecule, and the excess nucleosides are cut off by a specific endonuclease. The acid is then polymerized from ATP to form a polyA tail under the catalysis of polyA polymerase. This reaction occurs in the nucleus and can also continue in the cytoplasm.
(3) Base modification
There are a small number of rare bases (such as methylated bases) in the mRNA molecule that are chemically modified (such as methylation) after transcription. formed.