page_title: Non-coding RNA
section_title: History and discovery
hierarchical_section_title: Non-coding RNA / History and discovery
caption_attribution_description: English: X-ray structure of the tRNAPhe from yeast. Data was obtained by PDB: 1ehz&#8203; and rendered with PyMOL. violet: acceptor stem wine red: D-loop blue: anticodon loop orange: variable loop green: TPsiC-loop yellow: CCA-3' of the acceptor stem grey: anticodon Deutsch: Struktur der tRNAPhe aus Hefe. Dem Bild liegen die Daten aus PDB: 1ehz&#8203; zu Grunde, es wurde mittels PyMOL gerendert. violett: Akzeptorstamm weinrot: D-Schleife blau: Anticodonschleife orange: variable Schleife grün: TPsiC-Schleife gelb: CCA-3' des Akzeptorstammes grau: Anticodon Español: Estructura de rayos X de la tRNAPhe de la levadura. Los datos se obtuvieron por AP: 1ehz y se procesaron con PyMOL. violeta: vástago aceptor rojo vino: D-loop azul: lazo anticodón naranja: lazo variable verde: TPsiC-loop amarillo: CCA-3 'del vástago aceptor gris: anticodón
context_page_description: A non-coding RNA is an RNA molecule that is not translated into a protein. The DNA sequence from which a functional non-coding RNA is transcribed is often called an RNA gene. Abundant and functionally important types of non-coding RNAs include transfer RNAs and ribosomal RNAs, as well as small RNAs such as microRNAs, siRNAs, piRNAs, snoRNAs, snRNAs, exRNAs, scaRNAs and the long ncRNAs such as Xist and HOTAIR.
  The number of non-coding RNAs within the human genome is unknown; however, recent transcriptomic and bioinformatic studies suggest that there are thousands of them. Many of the newly identified ncRNAs have not been validated for their function. It is also likely that many ncRNAs are non functional, and are the product of spurious transcription.
  Non-coding RNAs are thought to contribute to diseases including cancer and Alzheimer's.
context_section_description: Nucleic acids were first discovered in 1868 by Friedrich Miescher and by 1939 RNA had been implicated in protein synthesis. Two decades later, Francis Crick predicted a functional RNA component which mediated translation; he reasoned that RNA is better suited to base-pair with an mRNA transcript than a pure polypeptide.
  The first non-coding RNA to be characterised was an alanine tRNA found in baker's yeast, its structure was published in 1965. To produce a purified alanine tRNA sample, Robert W. Holley et al. used 140kg of commercial baker's yeast to give just 1g of purified tRNAᴬˡᵃ for analysis. The 80 nucleotide tRNA was sequenced by first being digested with Pancreatic ribonuclease (producing fragments ending in Cytosine or Uridine) and then with takadiastase ribonuclease Tl (producing fragments which finished with Guanosine). Chromatography and identification of the 5' and 3' ends then helped arrange the fragments to establish the RNA sequence. Of the three structures originally proposed for this tRNA, the 'cloverleaf' structure was independently proposed in several following publications. The cloverleaf secondary structure was finalised  following X-ray crystallography analysis performed by two independent research groups in 1974.
  Ribosomal RNA was next to be discovered, followed by URNA in the early 1980s. Since then, the discovery of new non-coding RNAs has continued with snoRNAs, Xist, CRISPR and many more. Recent notable additions include riboswitches and miRNA; the discovery of the RNAi mechanism associated with the latter earned Craig C. Mello and Andrew Fire the 2006 Nobel Prize in Physiology or Medicine.
  Recent discoveries of ncRNAs have been achieved through both experimental and bioinformatic methods.
caption: The cloverleaf structure of Yeast tRNAPhe (inset) and the 3D structure determined by X-ray analysis.
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