Editing Gene expression (section)

===Protein transport===
Many proteins are destined for other parts of the cell than the cytosol and a wide range of signalling sequences or [[Signal peptide|(signal peptides)]] are used to direct proteins to where they are supposed to be.<ref>{{cite journal | vauthors = Lu J, Wu T, Zhang B, Liu S, Song W, Qiao J, Ruan H | title = Types of nuclear localization signals and mechanisms of protein import into the nucleus | journal = Cell Communication and Signaling | volume = 19 | issue = 1 | pages = 60 | date = May 2021 | pmid = 34022911 | pmc = 8140498 | doi = 10.1186/s12964-021-00741-y | doi-access = free }}</ref><ref>{{cite journal | vauthors = Lang S, Nguyen D, Bhadra P, Jung M, Helms V, Zimmermann R | title = Signal Peptide Features Determining the Substrate Specificities of Targeting and Translocation Components in Human ER Protein Import | journal = Frontiers in Physiology | volume = 13 | pages = 833540 | date = 2022-07-11 | pmid = 35899032 | pmc = 9309488 | doi = 10.3389/fphys.2022.833540 | doi-access = free }}</ref> In prokaryotes this is normally a simple process due to limited compartmentalisation of the cell.<ref>{{cite journal | vauthors = Murat D, Byrne M, Komeili A | title = Cell biology of prokaryotic organelles | journal = Cold Spring Harbor Perspectives in Biology | volume = 2 | issue = 10 | pages = a000422 | date = October 2010 | pmid = 20739411 | pmc = 2944366 | doi = 10.1101/cshperspect.a000422 }}</ref> However, in eukaryotes there is a great variety of different targeting processes to ensure the protein arrives at the correct organelle.<ref name=":0" />

Not all proteins remain within the cell and many are exported, for example, [[digestive enzymes]], [[hormone]]s and [[extracellular matrix]] proteins. In eukaryotes the export pathway is well developed and the main mechanism for the export of these proteins is translocation to the endoplasmic reticulum, followed by transport via the [[Golgi apparatus]].<ref name="Moreau2007">{{cite journal | vauthors = Moreau P, Brandizzi F, Hanton S, Chatre L, Melser S, Hawes C, Satiat-Jeunemaitre B | title = The plant ER-Golgi interface: a highly structured and dynamic membrane complex | journal = Journal of Experimental Botany | volume = 58 | issue = 1 | pages = 49–64 | year = 2007 | pmid = 16990376 | doi = 10.1093/jxb/erl135 | doi-access = free }}</ref><ref name="Prudovsky2008">{{cite journal | vauthors = Prudovsky I, Tarantini F, Landriscina M, Neivandt D, Soldi R, Kirov A, Small D, Kathir KM, Rajalingam D, Kumar TK | title = Secretion without Golgi | journal = Journal of Cellular Biochemistry | volume = 103 | issue = 5 | pages = 1327–1343 | date = April 2008 | pmid = 17786931 | pmc = 2613191 | doi = 10.1002/jcb.21513 }}</ref>