Editing Viroid (section)

===Retroviroids===
"Retroviroids", more formally "retroviroid-like elements", are viroid-like circular RNA sequences that are also found with homologous copies in the [[DNA]] genome of the host.<ref name="daros">{{cite journal| vauthors=Daròs JA, Flores R| title=Identification of a retroviroid-like element from plants. | journal=Proceedings of the National Academy of Sciences of the United States of America | year= 1995 | volume= 92 | issue= 15 | pages= 6856–6860 | pmid= 7542779| doi= 10.1073/pnas.92.15.6856| pmc= 41428| bibcode=1995PNAS...92.6856D | doi-access=free }}</ref> The only types found are closely related to the original "carnation small viroid-like RNA" (CarSV).<ref name="pmid11172112">{{cite journal |vauthors=Hegedűs K, Palkovics L, Tóth EK, Dallmann G, Balázs E |title=The DNA form of a retroviroid-like element characterized in cultivated carnation species |journal=The Journal of General Virology |volume=82 |issue=Pt 3 |pages=687–691 |date=March 2001 |pmid=11172112 |doi=10.1099/0022-1317-82-3-687 |url=|doi-access=free }}</ref><ref name="hegedus">{{cite journal| vauthors= Hegedűs K, Dallmann G, Balázs E| title=The DNA form of a retroviroid-like element is involved in recombination events with itself and with the plant genome. | journal=Virology| year= 2004 | volume= 325 | issue= 2 | pages= 277–286 | pmid= 15246267| doi= 10.1016/j.virol.2004.04.035| pmc= | doi-access= free}}</ref> These elements may act as a [[sequence homology|homologous]] substrate upon which [[genetic recombination|recombination]] may occur and are linked to [[DNA repair#Double-strand breaks|double-stranded break repair]].<ref name="hegedus"/><ref name=Truong>{{cite journal | vauthors = Truong LN, Li Y, Shi LZ, Hwang PY, He J, Wang H, Razavian N, Berns MW, Wu X | display-authors = 6 | title = Microhomology-mediated End Joining and Homologous Recombination share the initial end resection step to repair DNA double-strand breaks in mammalian cells | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 110 | issue = 19 | pages = 7720–25 | date = May 2013 | pmid = 23610439 | pmc = 3651503 | doi = 10.1073/pnas.1213431110 | bibcode = 2013PNAS..110.7720T | doi-access = free }}</ref>

These elements are dubbed retroviroids as the homologous DNA is generated by [[reverse transcriptase]] that is encoded by [[retrovirus]]es.<ref name="Flores-2014"/><ref>{{cite book | vauthors = Hull R | chapter = Chapter 5: Agents Resembling or Altering Virus Diseases | chapter-url = https://books.google.com/books?id=PYrZAAAAQBAJ&pg=PA199 |title=Plant virology |date= October 2013 |location=London, UK | publisher = Academic Press |isbn=978-0-12-384872-7 |edition=Fifth}}</ref> They are neither true viroids nor viroid-like [[satellite RNA]]s: there is no extracellular form of these elements; instead, they are spread only through pollen or egg-cells.<ref name=pmid35183574/> They appear to co-occur with a [[pararetrovirus]].<ref>{{cite journal |last1=Breit |first1=TM |last2=de Leeuw |first2=WC |last3=van Olst |first3=M |last4=Ensink |first4=WA |last5=van Leeuwen |first5=S |last6=Dekker |first6=RJ |title=Genome Sequence of a New Carnation Small Viroid-Like RNA, CarSV-1. |journal=Microbiology Resource Announcements |date=16 March 2023 |volume=12 |issue=3 |pages=e0121922 |doi=10.1128/mra.01219-22 |pmid=36840552 |pmc=10019309 |doi-access=free}}</ref>