Editing Nucleoside triphosphate (section)

== Nucleoside analogues ==
[[Nucleoside analogue]]s can be used to treat [[viral infections]].<ref name=":4">{{Cite web|url=http://www.mdpi.com/journal/molecules/special_issues/nucleoside_analogues|title=Nucleoside Analogues|website=Molecules|access-date=2017-11-13}}</ref> Nucleoside analogues are nucleosides that are structurally similar (analogous) to the nucleosides used in DNA and RNA synthesis.<ref>{{cite journal | vauthors = Jordheim LP, Durantel D, Zoulim F, Dumontet C | title = Advances in the development of nucleoside and nucleotide analogues for cancer and viral diseases | journal = Nature Reviews. Drug Discovery | volume = 12 | issue = 6 | pages = 447–64 | date = June 2013 | pmid = 23722347 | doi = 10.1038/nrd4010 | s2cid = 39842610 }}</ref> Once these nucleoside analogues enter a cell, they can become [[Phosphorylation|phosphorylated]] by a viral enzyme. The resulting nucleotides are similar enough to the nucleotides used in DNA or RNA synthesis to be incorporated into growing DNA or RNA strands, but they do not have an available 3' OH group to attach the next nucleotide, causing [[chain termination]].<ref>{{cite journal | vauthors = Ewald B, Sampath D, Plunkett W | title = Nucleoside analogs: molecular mechanisms signaling cell death | journal = Oncogene | volume = 27 | issue = 50 | pages = 6522–37 | date = October 2008 | pmid = 18955977 | doi = 10.1038/onc.2008.316 | s2cid = 23817516 | doi-access =  }}</ref> This can be exploited for therapeutic uses in viral infections because viral DNA polymerase recognizes certain nucleotide analogues more readily than eukaryotic DNA polymerase.<ref name=":4" /> For example, [[Zidovudine|azidothymidine]] is used in the treatment of [[HIV/AIDS]].<ref name=":10" /> Some less selective nucleoside analogues can be used as [[chemotherapy]] agents to treat cancer,<ref>{{cite journal | vauthors = Galmarini CM, Mackey JR, Dumontet C | title = Nucleoside analogues and nucleobases in cancer treatment | journal = The Lancet. Oncology | volume = 3 | issue = 7 | pages = 415–24 | date = July 2002 | pmid = 12142171 | doi=10.1016/s1470-2045(02)00788-x}}</ref> such as [[Cytarabine|cytosine arabinose]] (ara-C) in the treatment of certain forms of [[leukemia]].<ref name="Galmarini_2001" />

Resistance to nucleoside analogues is common, and is frequently due to a mutation in the enzyme that phosphorylates the nucleoside after entry into the cell.<ref name="Galmarini_2001">{{cite journal | vauthors = Galmarini CM, Mackey JR, Dumontet C | title = Nucleoside analogues: mechanisms of drug resistance and reversal strategies | journal = Leukemia | volume = 15 | issue = 6 | pages = 875–90 | year = 2001 | pmid = 11417472 | doi = 10.1038/sj.leu.2402114 | s2cid = 760764 | doi-access =  }}</ref> This is common in nucleoside analogues used to treat HIV/AIDS.<ref>{{cite journal | vauthors = Menéndez-Arias L | title = Mechanisms of resistance to nucleoside analogue inhibitors of HIV-1 reverse transcriptase | journal = Virus Research | volume = 134 | issue = 1–2 | pages = 124–46 | date = June 2008 | pmid = 18272247 | doi = 10.1016/j.virusres.2007.12.015 }}</ref>