Editing RNA (section)

=== RNA processing ===
[[File:Synthesis of Pseudouridine.svg|class=skin-invert-image|thumb|Uridine to pseudouridine is a common RNA modification.]]
Many RNAs are involved in modifying other RNAs.
[[Intron]]s are [[Splicing (genetics)|spliced]] out of [[pre-mRNA]] by [[spliceosome]]s, which contain several [[small nuclear RNA]]s (snRNA),<ref name=Biochemistry/> or the introns can be ribozymes that are spliced by themselves.<ref>{{cite journal | vauthors = Steitz TA, Steitz JA | title = A general two-metal-ion mechanism for catalytic RNA | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 90 | issue = 14 | pages = 6498–502 | date = July 1993 | pmid = 8341661 | pmc = 46959 | doi = 10.1073/pnas.90.14.6498 | bibcode = 1993PNAS...90.6498S | doi-access = free }}</ref>
RNA can also be altered by having its nucleotides modified to  nucleotides other than [[adenosine|A]], [[cytidine|C]], [[guanosine|G]] and [[uridine|U]].
In eukaryotes, modifications of RNA nucleotides are in general directed by [[small nucleolar RNA]]s (snoRNA; 60–300&nbsp;nt),<ref name=transcriptome>{{cite book|title=Mining the transcriptome&nbsp;– methods and applications|url=http://kth.diva-portal.org/smash/get/diva2:10803/FULLTEXT01 | vauthors = Wirta W |date=2006|isbn=978-91-7178-436-0|publisher=School of Biotechnology, Royal Institute of Technology|location=Stockholm|oclc=185406288}}</ref> found in the [[nucleolus]] and [[Cajal body|cajal bodies]]. snoRNAs associate with enzymes and guide them to a spot on an RNA by basepairing to that RNA. These enzymes then perform the nucleotide modification. rRNAs and tRNAs are extensively modified, but snRNAs and mRNAs can also be the target of base modification.<ref>{{cite journal | vauthors = Xie J, Zhang M, Zhou T, Hua X, Tang L, Wu W | title = Sno/scaRNAbase: a curated database for small nucleolar RNAs and cajal body-specific RNAs | journal = Nucleic Acids Research | volume = 35 | issue = Database issue | pages = D183–87 | date = January 2007 | pmid = 17099227 | pmc = 1669756 | doi = 10.1093/nar/gkl873 }}</ref><ref>{{cite journal | vauthors = Omer AD, Ziesche S, Decatur WA, Fournier MJ, Dennis PP | title = RNA-modifying machines in archaea | journal = Molecular Microbiology | volume = 48 | issue = 3 | pages = 617–29 | date = May 2003 | pmid = 12694609 | doi = 10.1046/j.1365-2958.2003.03483.x | s2cid = 20326977 | doi-access =  }}</ref> RNA can also be methylated.<ref>{{cite journal | vauthors = Cavaillé J, Nicoloso M, Bachellerie JP | title = Targeted ribose methylation of RNA in vivo directed by tailored antisense RNA guides | journal = Nature | volume = 383 | issue = 6602 | pages = 732–35 | date = October 1996 | pmid = 8878486 | doi = 10.1038/383732a0 | bibcode = 1996Natur.383..732C | s2cid = 4334683 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Kiss-László Z, Henry Y, Bachellerie JP, Caizergues-Ferrer M, Kiss T | title = Site-specific ribose methylation of preribosomal RNA: a novel function for small nucleolar RNAs | journal = Cell | volume = 85 | issue = 7 | pages = 1077–88 | date = June 1996 | pmid = 8674114 | doi = 10.1016/S0092-8674(00)81308-2 | s2cid = 10418885 | doi-access = free }}</ref>