Editing Messenger RNA (section)

===Transport===
Another difference between eukaryotes and prokaryotes is mRNA transport. Because eukaryotic transcription and translation is compartmentally separated, eukaryotic mRNAs must be exported from the [[cell nucleus|nucleus]] to the [[cytoplasm]]—a process that may be regulated by different signaling pathways.<ref name=Quaresma2013>{{cite journal | vauthors = Quaresma AJ, Sievert R, Nickerson JA | title = Regulation of mRNA export by the PI3 kinase/AKT signal transduction pathway | journal = Molecular Biology of the Cell | volume = 24 | issue = 8 | pages = 1208–1221 | date = April 2013 | pmid = 23427269 | pmc = 3623641 | doi = 10.1091/mbc.E12-06-0450 }}</ref> Mature mRNAs are recognized by their processed modifications and then exported through the [[nuclear pore]] by binding to the cap-binding proteins CBP20 and CBP80,<ref name=kierzkowski2009>{{cite journal | vauthors = Kierzkowski D, Kmieciak M, Piontek P, Wojtaszek P, Szweykowska-Kulinska Z, Jarmolowski A | title = The Arabidopsis CBP20 targets the cap-binding complex to the nucleus, and is stabilized by CBP80 | journal = The Plant Journal | volume = 59 | issue = 5 | pages = 814–825 | date = September 2009 | pmid = 19453442 | doi = 10.1111/j.1365-313X.2009.03915.x | doi-access = free }}</ref> as well as the transcription/export complex (TREX).<ref name=strausser2002>{{cite journal | vauthors = Strässer K, Masuda S, Mason P, Pfannstiel J, Oppizzi M, Rodriguez-Navarro S, Rondón AG, Aguilera A, Struhl K, Reed R, Hurt E | title = TREX is a conserved complex coupling transcription with messenger RNA export | journal = Nature | volume = 417 | issue = 6886 | pages = 304–308 | date = May 2002 | pmid = 11979277 | doi = 10.1038/nature746 | bibcode = 2002Natur.417..304S | s2cid = 1112194 }}</ref><ref name=katahira2014>{{cite journal | vauthors = Katahira J, Yoneda Y | title = Roles of the TREX complex in nuclear export of mRNA | journal = RNA Biology | volume = 6 | issue = 2 | pages = 149–152 | date = 27 October 2014 | pmid = 19229134 | doi = 10.4161/rna.6.2.8046 | doi-access = free }}</ref> Multiple mRNA export pathways have been identified in eukaryotes.<ref name="Cenik2011">{{cite journal | vauthors = Cenik C, Chua HN, Zhang H, Tarnawsky SP, Akef A, Derti A, Tasan M, Moore MJ, Palazzo AF, Roth FP | title = Genome analysis reveals interplay between 5'UTR introns and nuclear mRNA export for secretory and mitochondrial genes | journal = PLOS Genetics | volume = 7 | issue = 4 | pages = e1001366 | date = April 2011 | pmid = 21533221 | pmc = 3077370 | doi = 10.1371/journal.pgen.1001366 | doi-access = free }}</ref>

In spatially complex cells, some mRNAs are transported to particular subcellular destinations. In mature [[neuron]]s, certain mRNA are transported from the [[Soma (biology)|soma]] to [[dendrite]]s. One site of mRNA translation is at polyribosomes selectively localized beneath synapses.<ref>{{cite journal | vauthors = Steward O, Levy WB | title = Preferential localization of polyribosomes under the base of dendritic spines in granule cells of the dentate gyrus | journal = The Journal of Neuroscience | volume = 2 | issue = 3 | pages = 284–291 | date = March 1982 | pmid = 7062109 | pmc = 6564334 | doi = 10.1523/JNEUROSCI.02-03-00284.1982 }}</ref> The mRNA for [[Arc/Arg3.1]] is induced by synaptic activity and localizes selectively near active [[synapse]]s based on signals generated by [[NMDA receptor]]s.<ref>{{cite journal | vauthors = Steward O, Worley PF | title = Selective targeting of newly synthesized Arc mRNA to active synapses requires NMDA receptor activation | journal = Neuron | volume = 30 | issue = 1 | pages = 227–240 | date = April 2001 | pmid = 11343657 | doi = 10.1016/s0896-6273(01)00275-6 | s2cid = 13395819 | doi-access = free }}</ref> Other mRNAs also move into dendrites in response to external stimuli, such as [[β-actin]] mRNA.<ref name=Job1912>{{cite journal | vauthors = Job C, Eberwine J | title = Localization and translation of mRNA in dendrites and axons | journal = Nature Reviews. Neuroscience | volume = 2 | issue = 12 | pages = 889–898 | date = December 2001 | pmid = 11733796 | doi = 10.1038/35104069 | author-link2 = James Eberwine | s2cid = 5275219 }}</ref> For export from the nucleus, actin mRNA associates with [[ZBP1]]<ref name=Oleynikov2003>{{cite journal | vauthors = Oleynikov Y, Singer RH | title = Real-time visualization of ZBP1 association with beta-actin mRNA during transcription and localization  | journal = Current Biology | volume = 13 | issue = 3 | pages = 199–207 | date = February 2003 | pmid =  12573215 | pmc = 4765734 | doi = 10.1016/s0960-9822(03)00044-7 | bibcode = 2003CBio...13..199O }}</ref> and later with [[Eukaryotic small ribosomal subunit (40S)|40S subunit]]. The complex is bound by a [[motor protein]] and is transported to the target location ([[Neurite|neurite extension]]) along the [[cytoskeleton]]. Eventually ZBP1 is [[Phosphorylation|phosphorylated]] by [[Src family kinase|Src]] in order for translation to be initiated.<ref name="Hüttelmaier_2005">{{cite journal | vauthors = Hüttelmaier S, Zenklusen D, Lederer M, Dictenberg J, Lorenz M, Meng X, Bassell GJ, Condeelis J, Singer RH | display-authors = 6 | title = Spatial regulation of beta-actin translation by Src-dependent phosphorylation of ZBP1 | journal = Nature | volume = 438 | issue = 7067 | pages = 512–515 | date = November 2005 | pmid = 16306994 | doi = 10.1038/nature04115 | s2cid = 2453397 | bibcode = 2005Natur.438..512H }}</ref> In developing neurons, mRNAs are also transported into growing [[axon]]s and especially growth cones. Many mRNAs are marked with so-called "zip codes", which target their transport to a specific location.<ref name=Oleynikov1998>{{cite journal | vauthors = Oleynikov Y, Singer RH | title = RNA localization: different zipcodes, same postman? | journal = Trends in Cell Biology | volume = 8 | issue = 10 | pages = 381–383 | date = October 1998 | pmid =  9789325 | pmc = 2136761 | doi = 10.1016/s0962-8924(98)01348-8 }}</ref><ref name=Ainger1997>{{cite journal | vauthors = Ainger K, Avossa D, Diana AS, Barry C, Barbarese E, Carson JH | title = Transport and localization elements in myelin basic protein mRNA | journal = The Journal of Cell Biology | volume = 138 | issue = 5 | pages = 1077–1087 | date = September 1997 | pmid = 9281585 | pmc = 2136761 | doi = 10.1083/jcb.138.5.1077 }}</ref> mRNAs can also transfer between mammalian cells through structures called [[tunneling nanotube]]s.<ref>{{cite journal | vauthors = Haimovich G, Ecker CM, Dunagin MC, Eggan E, Raj A, Gerst JE, Singer RH | title = Intercellular mRNA trafficking via membrane nanotube-like extensions in mammalian cells | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 114 | issue = 46 | pages = E9873–E9882 | date = November 2017 | pmid = 29078295 | pmc = 5699038 | doi = 10.1073/pnas.1706365114 | bibcode = 2017PNAS..114E9873H | doi-access = free }}</ref><ref>{{Cite journal | vauthors = Haimovich G, Dasgupta S, Gerst JE  |title=RNA transfer through tunneling nanotubes | journal = Biochemical Society Transactions | date = February 2021| volume = 49 | issue = 1 | pages = 145–160 |url=https://portlandpress.com/biochemsoctrans/article-abstract/49/1/145/227426/RNA-transfer-through-tunneling-nanotubes |doi=10.1042/BST20200113|pmid=33367488 |s2cid=229689880 }}</ref>