Editing RNA world (section)

== Implications ==
The RNA world hypothesis, if true, has important implications for the [[definition of life]] and the [[Abiogenesis|origin of life]]. For most of the time that followed [[Rosalind Franklin|Franklin]], [[James D. Watson|Watson]] and [[Francis Crick|Crick]]'s elucidation of DNA structure in 1953, life was largely defined in terms of DNA and proteins: DNA and proteins seemed the dominant macromolecules in the living cell, with RNA only aiding in creating proteins from the DNA blueprint.

The RNA world hypothesis places RNA at center-stage when life originated. The RNA world hypothesis is supported by the observations that ribosomes are ribozymes:<ref>{{cite journal | vauthors = Fox GE | title = Origin and evolution of the ribosome | journal = Cold Spring Harbor Perspectives in Biology | volume = 2 | issue = 9 | pages = a003483 | date = September 2010 | pmid = 20534711 | pmc = 2926754 | doi = 10.1101/cshperspect.a003483 | doi-access = free }}</ref><ref>{{cite book | first1 = GE | last1 = Fox| veditors = Hernández G, Jagus R| year = 2016| title = Evolution of the Protein Synthesis Machinery and Its Regulation| chapter= Origins and early evolution of the ribosome |pages=31–60|location = Switzerland  | publisher = Springer, Cham| doi = 10.1007/978-3-319-39468-8| isbn=978-3-319-39468-8 | s2cid = 27493054}}</ref> the catalytic site is composed of RNA, and proteins hold no major structural role and are of peripheral functional importance. This was confirmed with the deciphering of the 3-dimensional structure of the ribosome in 2001. Specifically, peptide bond formation, the reaction that binds [[amino acid]]s together into [[protein]]s, is now known to be catalyzed by an adenine residue in the [[rRNA]].

RNAs are known to play roles in other cellular catalytic processes, specifically in the targeting of enzymes to specific RNA sequences.  In eukaryotes, the processing of [[pre-mRNA]] and [[RNA editing]] take place at sites determined by the base pairing between the target RNA and RNA constituents of [[snRNP|small nuclear ribonucleoproteins (snRNPs)]].  Such enzyme targeting is also responsible for gene down regulation through [[RNA interference]] (RNAi), where an enzyme-associated guide RNA targets specific mRNA for selective destruction.  Likewise, in eukaryotes the maintenance of [[telomeres]] involves copying of an RNA template that is a constituent part of the [[telomerase]] ribonucleoprotein enzyme.  Another cellular organelle, the [[Vault (organelle)|vault]], includes a ribonucleoprotein component, although the function of this organelle remains to be elucidated.