Editing Gene expression (section)

===Post-transcriptional regulation===
{{main|Post-transcriptional regulation}}
In eukaryotes, where export of RNA is required before translation is possible, nuclear export is thought to provide additional control over gene expression. All transport in and out of the nucleus is via the [[nuclear pore]] and transport is controlled by a wide range of [[importin]] and [[exportin]] proteins.<ref>{{cite journal | vauthors = De Magistris P | title = The Great Escape: mRNA Export through the Nuclear Pore Complex | journal = International Journal of Molecular Sciences | volume = 22 | issue = 21 | pages = 11767 | date = October 2021 | pmid = 34769195 | pmc = 8583845 | doi = 10.3390/ijms222111767 | doi-access = free }}</ref>

Expression of a gene coding for a protein is only possible if the messenger RNA carrying the code survives long enough to be translated.<ref name=":0">{{Citation | vauthors =  Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P |title=From RNA to Protein |date=2002 |work=Molecular Biology of the Cell. 4th edition |url=https://www.ncbi.nlm.nih.gov/books/NBK26829/ |access-date=2024-06-10 |publisher=Garland Science |language=en }}</ref> In a typical cell, an RNA molecule is only stable if specifically protected from degradation.<ref>{{cite journal | vauthors = Liu H, Luo M, Wen JK | title = mRNA stability in the nucleus | journal = Journal of Zhejiang University. Science. B | volume = 15 | issue = 5 | pages = 444–454 | date = May 2014 | pmid = 24793762 | pmc = 4076601 | doi = 10.1631/jzus.B1400088 }}</ref> RNA degradation has particular importance in regulation of expression in eukaryotic cells where mRNA has to travel significant distances before being translated.<ref>{{cite journal | vauthors = Yan LL, Zaher HS | title = How do cells cope with RNA damage and its consequences? | journal = The Journal of Biological Chemistry | volume = 294 | issue = 41 | pages = 15158–15171 | date = October 2019 | pmid = 31439666 | pmc = 6791314 | doi = 10.1074/jbc.REV119.006513 | doi-access = free }}</ref> In eukaryotes, RNA is stabilised by certain post-transcriptional modifications, particularly the [[5′ cap]] and [[polyadenylation|poly-adenylated tail]].<ref>{{cite journal | vauthors = Passmore LA, Coller J | title = Roles of mRNA poly(A) tails in regulation of eukaryotic gene expression | journal = Nature Reviews. Molecular Cell Biology | volume = 23 | issue = 2 | pages = 93–106 | date = February 2022 | pmid = 34594027 | pmc = 7614307 | doi = 10.1038/s41580-021-00417-y }}</ref>

Intentional degradation of mRNA is used not just as a defence mechanism from foreign RNA (normally from viruses) but also as a route of mRNA ''destabilisation''.<ref>{{cite journal | vauthors = Shehata SI, Watkins JM, Burke JM, Parker R | title = Mechanisms and consequences of mRNA destabilization during viral infections | journal = Virology Journal | volume = 21 | issue = 1 | pages = 38 | date = February 2024 | pmid = 38321453 | pmc = 10848536 | doi = 10.1186/s12985-024-02305-1 | doi-access = free }}</ref> If an mRNA molecule has a complementary sequence to a [[small interfering RNA]] then it is targeted for destruction via the [[RNA interference]] pathway.<ref>{{cite journal | vauthors = Tang L, Chen HY, Hao NB, Tang B, Guo H, Yong X, Dong H, Yang SM | title = microRNA inhibitors: Natural and artificial sequestration of microRNA | journal = Cancer Letters | volume = 407 | pages = 139–147 | date = October 2017 | pmid = 28602827 | pmc = 7152241 | doi = 10.1016/B978-0-444-64046-8.00282-2 | isbn = 978-0-444-64047-5 }}</ref>