Editing Messenger RNA (section)

===Eukaryotic mRNA turnover===
Inside eukaryotic cells, there is a balance between the processes of [[Translation (genetics)|translation]] and mRNA decay. Messages that are being actively translated are bound by [[ribosome]]s, the [[eukaryotic initiation factor]]s [[eIF-4E]] and [[eIF-4G]], and [[poly(A)-binding protein]]. eIF-4E and eIF-4G block the decapping enzyme ([[DCP2]]), and poly(A)-binding protein blocks the [[exosome complex]], protecting the ends of the message. The balance between translation and decay is reflected in the size and abundance of cytoplasmic structures known as [[P-bodies]].<ref name=Parker2007>{{cite journal | vauthors = Parker R, Sheth U | title = P bodies and the control of mRNA translation and degradation | journal = Molecular Cell | volume = 25 | issue = 5 | pages = 635–646 | date = March 2007 | pmid = 17349952 | doi = 10.1016/j.molcel.2007.02.011 | doi-access = free }}</ref> The [[polyadenylation|poly(A) tail]] of the mRNA is shortened by specialized exonucleases that are targeted to specific messenger RNAs by a combination of cis-regulatory sequences on the RNA and trans-acting RNA-binding proteins. Poly(A) tail removal is thought to disrupt the circular structure of the message and destabilize the [[cap binding complex]]. The message is then subject to degradation by either the [[exosome complex]] or the [[decapping complex]]. In this way, translationally inactive messages can be destroyed quickly, while active messages remain intact. The mechanism by which translation stops and the message is handed-off to decay complexes is not understood in detail. The majority of mRNA decay was believed to be cytoplasmic; however, recently, a novel mRNA decay pathway was described, which starts in the nucleus.<ref name=Chattopadhyay2022>{{cite journal | vauthors = Chattopadhyay S, Garcia Martinez J, Haimovich G, Fischer J, Khwaja A, Barkai O, Chuartzman SG, Schuldiner M, Elran R, Rosenberg M, Urim S, Deshmukh S, Bohnsack K, Bohnsack M, Perez Ortin J, Choder M | title = RNA-controlled nucleocytoplasmic shuttling of mRNA decay factors regulates mRNA synthesis and a novel mRNA decay pathway | journal = Nature Communications | volume = 13(1): 7184 | date = November 2022 | issue = 1 | page = 7184 | pmid = 36418294 | doi = 10.1038/s41467-022-34417-z | doi-access = free | pmc = 9684461 | bibcode = 2022NatCo..13.7184C }}</ref>