After transcription, the preliminary, unprocessed mRNA is known as precursor mRNA, or heterogeneous nuclear RNA (hnRNA).
Eukaryotic pre-mRNA undergoes significant post-transcriptional processing before leaving the nucleus, including 5'-capping, poly A tail addition, and intron splicing.
Then, it leaves the nucleus bound to specific packaging protiens which then associate with ribosomes to undergo translation
However, certain mRNA sequences instead associate with proteins that are found in P bodies. (in the cytoplasm)
(They are like QC center for newly synthesized mRNA)
P bodies are distinct foci found within eukaryotic cells that are involved in mRNA regulation and turnover.
They play a fundamental role in translation repression and mRNA decay, and contain numerous proteins including RNA exonucleases, mRNA decapping enzymes, and constituents involved in mRNA quality control and microRNA-induced mRNA silencing.
?also for mRNA storage, for translation later when necessary
7-methyl-G-cap protects mRNA from degradation by cellular exonucleases, and allows it to exit the nucleus.
The addition of poly A tail occurs before the mRNA exits the nucleus. In the cytosol, the poly A tail is gradually shortened, eventually leading to mRNA degradation.
Eukaryotic translation initiation requires:
The Kozak consensus sequence occurs on eukaryotic mRNA and is defined by the following sequence: (gcc)gccRccAUGG, where R is either adenine or guanine.
When the methionine codon (AUG) is positioned near the beginning of a mRNA molecule and is surrounded by the Kozak sequence, it serves as the initiator for translation (i.e mRNA binding to ribosomes).