Rna

For other uses, see RNA (disambiguation).

A hairpin loop from a pre-mRNA. Notice its nitrogen-rich (blue) bases and oxygen-rich (red) backbone.

Ribonucleic acid or RNA is a nucleic acid made from a long chain of nucleotide units. Each nucleotide consists of a nitrogenous base, a ribose sugar, and a phosphate. RNA is very similar to DNA, but differs in a few important structural details: in the cell RNA is usually single stranded, while DNA is usually double stranded. RNA nucleotides contain ribose while DNA contains deoxyribose (a type of ribose that lacks one oxygen atom), and in RNA the nucleotide uracil substitutes for thymine, which is present in DNA.

RNA is transcribed from DNA by enzymes called RNA polymerases and is generally further processed by other enzymes. Some of these RNA-processing enzymes contain RNA as part of their structures. RNA is also central to the translation of some RNAs into proteins. In this process, a type of RNA called messenger RNA carries information from DNA to structures called ribosomes. These ribosomes are made from proteins and ribosomal RNAs, which come together to form a molecular machine that can and read messenger RNAs and translate the information they carry into proteins. It has also been known since the 1990s that several types of RNA regulate which genes are active.

Contents 1 Structure 2 Comparison with DNA 3 Synthesis 4 Types of RNA 4.1 Overview 4.2 In translation 4.3 In gene regulation 4.4 In RNA processing 4.5 List of RNAs 5 Discovery 6 See also 7 References 8 External links

Structure

Watson-Crick base pairs in a siRNA (hydrogen atoms are not shown)

Each nucleotide in RNA contains a ribose sugar, with carbons numbered 1\' through 5\'. A base is attached to the 1\' position, generally adenine (A), cytosine (C), guanine (G) or uracil (U). A phosphate group is attached to the 3\' position of one ribose and the 5\' position of the next. The phosphate groups have a negative charge each at physiological pH, making RNA a charged molecule (polyanion). The bases may form hydrogen bonds between cytosine and guanine, between adenine and uracil and between guanine and uracil. However other interactions are possible, such as a group of adenine bases binding to each other in a bulge,Barciszewski J, Frederic B, Clark C (1999). RNA biochemistry and biotechnology. Springer, 73–87. ISBN 0792358627.  or the GNRA tetraloop that has a guanine–adenine base-pair.Lee JC, Gutell RR (2004). "Diversity of base-pair conformations and their occurrence in rRNA structure and RNA structural motifs". J. Mol. Biol. 344 (5): 1225–49. doi:10.1016/j.jmb.2004.09.072. PMID 15561141. 

Chemical structure of RNA

An important structural feature of RNA that distinguishes it from DNA is the presence of a hydroxyl group at the 2\' position of the ribose sugar. The presence of this functional group enforces the C3\'-endo sugar conformation (as opposed to the C2\'-endo conformation of the deoxyribose sugar in DNA) that causes the helix to adopt the A-form geometry rather than the B-form most commonly observed in DNA.Salazar M, Fedoroff OY, Miller JM, Ribeiro NS, Reid BR (1992). "The DNA strand in DNAoRNA hybrid duplexes is neither B-form nor A-form in solution". Biochemistry 1993 (32): 4207–15. PMID 7682844.  This results in a very deep and narrow major groove and a shallow and wide minor groove.Hermann T, Patel DJ (2000). "RNA bulges as architectural and recognition motifs". Structure 8 (3): R47–R54. doi:10.1016/S0969-2126(00)00110-6.  A second consequence of the presence of the 2\'-hydroxyl group is that in conformationally flexible regions of an RNA molecule (that is, not involved in formation of a double helix), it can chemically attack the adjacent phosphodiester bond to cleave the backbone.Mikkola S, Nurmi K, Yousefi-Salakdeh E, Strömberg R, Lönnberg H (1999). "The mechanism of the metal ion promoted cleavage of RNA phosphodiester bonds involves a general acid catalysis by the metal aquo ion on the departure of the leaving group". Perkin transactions 2: 1619–26. doi:10.1039/a903691a. 

RNA is transcribed with only four bases (adenine, cytosine, guanine and uracil),Jankowski JAZ, Polak JM (1996). Clinical gene analysis and manipulation: tools, techniques and troubleshooting. Cambridge University Press, 14. ISBN 0521478960.  but there are numerous modified bases and sugars in mature RNAs. Pseudouridine (Ψ), in which the linkage between uracil and ribose is changed from a C–N bond to a C–C bond, and ribothymidine (T), are found in various places (most notably in the TΨC loop of tRNA).Yu Q, Morrow CD (2001). "Identification of critical elements in the tRNA acceptor stem and TΨC loop necessary for human immunodeficiency virus type 1 infectivity". J Virol. 75 (10): 4902–6. doi:10.1128/JVI.75.10.4902-4906.2001.  Another notable modified base is hypoxanthine, a deaminated guanine base whose nucleoside is called inosine. Inosine plays a key role in the wobble hypothesis of the genetic code.Elliott MS, Trewyn RW (1983). "Inosine biosynthesis in transfer RNA by an enzymatic insertion of hypoxanthine". J. Biol. Chem. 259 (4): 2407–10. PMID 6365911.  There are nearly 100 other naturally occurring modified nucleosides,Söll D, RajBhandary U (1995). tRNA: Structure, biosynthesis, and function. ASM Press, 165. ISBN 155581073X.  of which pseudouridine and nucleosides with 2\'-O-methylribose are the most common.Kiss T (2001). "Small nucleolar RNA-guided post-transcriptional modification of cellular RNAs". The EMBO Journal 20: 3617–22. doi:10.1093/emboj/20.14.3617.  The specific roles of many of these modifications in RNA are not fully understood. However, it is notable that in ribosomal RNA, many of the post-transcriptional modifications occur in highly functional regions, such as the peptidyl transferase center and the subunit interface, implying that they are important for normal function.King TH, Liu B, McCully RR, Fournier MJ (2002). "Ribosome structure and activity are altered in cells lacking snoRNPs that form pseudouridines in the peptidyl transferase center". Molecular Cell 11 (2): 425–35. doi:10.1016/S1097-2765(03)00040-6. 

Secondary structure of an RNA from a telomerase

The functional form of single stranded RNA molecules, just like proteins, frequently requires a specific tertiary structure. The scaffold for this structure is provided by secondary structural elements which are hydrogen bonds within the molecule. This leads to several recognizable "domains" of secondary structure like hairpin loops, bulges and internal loops.Mathews DH, Disney MD, Childs JL, Schroeder SJ, Zuker M, Turner DH (2004). "Incorporating chemical modification constraints into a dynamic programming algorithm for prediction of RNA secondary structure". Proc. Natl. Acad. Sci. USA 101 (19): 7287–92. doi:10.1073/pnas.0401799101.  There has been a significant amount of research directed at the RNA structure prediction problem.

Comparison with DNA

RNA and DNA differ in three main ways. First, unlike DNA which is double-stranded, RNA is a single-stranded molecule in most of its biological roles and has a much shorter chain of nucleotides. Second, while DNA contains deoxyribose, RNA contains ribose, (there is no hydroxyl group attached to the pentose ring in the 2\' position in DNA, whereas RNA has two hydroxyl groups). These hydroxyl groups make RNA less stable than DNA because it is more prone to hydrolysis. Third, the complementary nucleotide to adenine is not thymine, as it is in DNA, but rather uracil, which is an unmethylated form of thymine.

The 50S ribosomal subunit. RNA is in orange, protein in blue. The active site is in the middle (red).

Like DNA, most biologically active RNAs including tRNA, rRNA, snRNAs and other non-coding RNAs are extensively base paired to form double stranded helices. Structural analysis of these RNAs have revealed that they are highly structured. Unlike DNA, this structure is not long double-stranded helices but rather collections of short helices packed together into structures akin to proteins. In this fashion, RNAs can achieve chemical catalysis, like enzymes.Higgs PG (2000). "RNA secondary structure: physical and computational aspects". Quarterly Reviews of Biophysics 33: 199–253. doi:10.1017/S0033583500003620.  For instance, determination of the structure of the ribosome—an enzyme that catalyzes peptide bond formation—revealed that its active site is composed entirely of RNA.Nissen P, Hansen J, Ban N, Moore PB, Steitz TA (2000). "The structural basis of ribosome activity in peptide bond synthesis". Science 289 (5481): 920–30. doi:10.1126/science.289.5481.920. 

Synthesis

Synthesis of RNA is usually catalyzed by an enzyme—RNA polymerase—using DNA as a template. Initiation of synthesis begins with the binding of the enzyme to a promoter sequence in the DNA (usually found "upstream" of a gene). The DNA double helix is unwound by the helicase activity of the enzyme. The enzyme then progresses along the template strand in the 3’ to 5’ direction, synthesizing a complementary RNA molecule with elongation occurring in the 5’ to 3’ direction. The DNA sequence also dictates where termination of RNA synthesis will occur.Nudler E, Gottesman ME (2002). "Transcription termination and anti-termination in E. coli". Genes to Cells 7: 755–68. doi:10.1046/j.1365-2443.2002.00563.x. 

There are also a number of RNA-dependent RNA polymerases as well that use RNA as their template for synthesis of a new strand of RNA. For instance, a number of RNA viruses (such as poliovirus) use this type of enzyme to replicate their genetic material.Jeffrey L Hansen, Alexander M Long, Steve C Schultz (1997). "Structure of the RNA-dependent RNA polymerase of poliovirus". Structure 5 (8): 1109-22. doi:10.1016/S0969-2126(97)00261-X.  Also, it is known that RNA-dependent RNA polymerases are required for the RNA interference pathway in many organisms.Ahlquist P (2002). "RNA-Dependent RNA Polymerases, Viruses, and RNA Silencing". Science 296 (5571): 1270–73. doi:10.1126/science.1069132. 

Types of RNA

Overview

Structure of a hammerhead ribozyme, a ribozyme that cuts RNA

Messenger RNA (mRNA) is the RNA that carries information from DNA to the ribosome sites of protein synthesis (translation) in the cell. The coding sequence of the mRNA determines the amino acid sequence in the protein that is produced.

RNA genes are genes that encode RNA which is not translated into a protein, known as non-coding RNA or small RNA. Non-coding RNAs can also derive from introns. The most prominent examples of non-coding RNAs are transfer RNA (tRNA) and ribosomal RNA (rRNA), both of which are involved in the process of translation.Berg JM, Tymoczko JL, Stryer L (2002). Biochemistry, 5th edition, WH Freeman and Company, 118–19, 781–808. ISBN 0-7167-4684-0.  There are also non-coding RNAs involved in gene regulation, RNA processing and other roles. Certain RNAs are able to catalyse chemical reactions such as cutting and ligating other RNA molecules,Rossi JJ (2004). "Ribozyme diagnostics comes of age". Chemistry & Biology 11 (7): 894–95. doi:10.1016/j.chembiol.2004.07.002.  and the catalysis of peptide bond formation in the ribosome; these are known as ribozymes.

Double-stranded RNA (dsRNA) is RNA with two complementary strands, similar to the DNA found in all cells. dsRNA forms the genetic material of some viruses (double-stranded RNA viruses). In eukaryotes, long double-stranded RNA such as viral RNA can trigger RNA interference, where short dsRNA molecules called siRNAs (small interfering RNAs) can silence the expression of genes.Blevins T et al (2006). "Four plant Dicers mediate viral small RNA biogenesis and DNA virus induced silencing". Nucleic Acids Res 34 (21): 6233–46. PMID 17090584. 

In translation

Messenger RNA (mRNA) carries information about a protein sequence to the ribosomes, the protein synthesis factories in the cell. It is coded so that every three nucleotides (a codon) correspond to one amino acid. In eukaryotic cells, once precursor mRNA (pre-mRNA) has been transcribed from DNA, it is processed to mature mRNA. This removes its introns—non-coding sections of the pre-mRNA. The mRNA is then exported from the nucleus to the cytoplasm, where it is bound to ribosomes and translated into its corresponding protein form with the help of tRNA. In prokaryotic cells, which do not have nucleus and cytoplasm compartments, mRNA can bind to ribosomes while it is being transcribed from DNA. After a certain amount of time the message degrades into its component nucleotides with the assistance of ribonucleases.

Transfer RNA (tRNA) is a small RNA chain of about 80 nucleotides that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. It has sites for amino acid attachment and an anticodon region for codon recognition that binds to a specific sequence on the messenger RNA chain through hydrogen bonding.

Ribosomal RNA (rRNA) is the catalytic component of the ribosomes. Eukaryotic ribosomes contain four different rRNA molecules: 18S, 5.8S, 28S and 5S rRNA. Three of the rRNA molecules are synthesized in the nucleolus, and one is synthesized elsewhere. In the cytoplasm, ribosomal RNA and protein combine to form a nucleoprotein called a ribosome. The ribosome binds mRNA and carries out protein synthesis. Several ribosomes may be attached to a single mRNA at any time.Cooper GC, Hausman RE (2004). The Cell: A Molecular Approach, 3rd edition, Sinauer, 261–76, 297, 339–44. ISBN 0-87893-214-3.  rRNA is extremely abundant and makes up 80% of the 10 mg/ml RNA found in a typical eukaryotic cytoplasm.Kampers T, Friedhoff P, Biernat J, Mandelkow E-M, Mandelkow E (1996). "RNA stimulates aggregation of microtubule-associated protein tau into Alzheimer-like paired helical filaments". FEBS Letters 399: 98–100, 344–49. PMID 8985176. 

In gene regulation

Several types of RNA can downregulate gene expression by being complementary to a part of a gene. MicroRNAs (miRNA; 21-22 nt) are found in eukaryotes and act through RNA interference (RNAi), where an effector complex of miRNA and enzymes can break down mRNA which the miRNA is complementary to, block the mRNA from being translated, or cause the promoter to be methylated which generally downregulates the gene.Matzke MA, Matzke AJM (2004). "Planting the seeds of a new paradigm". PLoS Biology 2 (5): e133. doi:10.1371/journal.pbio.0020133.  Some miRNAs upregulate genes instead (RNA activation).Check E (2007). "RNA interference: hitting the on switch". Nature 448 (7156): 855–58. doi:10.1038/448855a.  While small interfering RNAs (siRNA; 20-25 nt) are often produced by breakdown of viral RNA, there are also endogenous sources of siRNAs.Vazquez F, Vaucheret H, Rajagopalan R, Lepers C, Gasciolli V, Mallory AC, Hilbert J, Bartel DP, Crété P (2004). "Endogenous trans-acting siRNAs regulate the accumulation of Arabidopsis mRNAs". Molecular Cell 16 (1): 69–79. doi:10.1016/j.molcel.2004.09.028.  siRNAs act through RNA interference in a fashion similar to miRNAs, including RNA activation.Doran G (2007). "RNAi – Is one suffix sufficient?". Journal of RNAi and Gene Silencing 3 (1): 217–19.  Animals have Piwi-interacting RNAs (piRNA; 29-30 nt) which are active in germline cells and are thought to be a defense against transposons and play a role in gametogenesis.Horwich MD, Li C Matranga C, Vagin V, Farley G, Wang P, Zamore PD (2007). "The Drosophila RNA methyltransferase, DmHen1, modifies germline piRNAs and single-stranded siRNAs in RISC". Current Biology 17: 1265–72. doi:10.1016/j.cub.2007.06.030. Girard A, Sachidanandam R, Hannon GJ, Carmell MA (2006). "A germline-specific class of small RNAs binds mammalian Piwi proteins". Nature 442: 199–202. doi:10.1038/nature04917.  X chromosome inactivation in female mammals is caused by Xist, an RNA which coats one X chromosome, inactivating it.Heard E, Mongelard F, Arnaud D, Chureau C, Vourc\'h C, Avner P (1999). "Human XIST yeast artificial chromosome transgenes show partial X inactivation center function in mouse embryonic stem cells". Proc. Natl. Acad. Sci. USA 96 (12): 6841–46. PMID 10359800.  Antisense RNAs are widespread among bacteria; most downregulate a gene, but a few are activators of transcription.Wagner EG, Altuvia S, Romby P (2002). "Antisense RNAs in bacteria and their genetic elements". Adv Genet. 46: 361–98. PMID 11931231.  An mRNA may contain regulatory elements itself, such as riboswitches, in the 5\' UTR or 3\' UTR; these cis-regulatory elements regulate the activity of that mRNA.Batey RT (2006). "Structures of regulatory elements in mRNAs". Curr. Opin. Struct. Biol. 16 (3): 299–306. doi:10.1016/j.sbi.2006.05.001. PMID 16707260. 

Uridine to pseudouridine is a common RNA modification.

In RNA processing

Many RNAs are involved in modifying other RNAs. Introns are spliced out of pre-mRNA by spliceosomes, which contain several small nuclear RNAs (snRNA). RNA can also be altered by having its nucleotides modified to other nucleotides than A, C, G and U. In eukaryotes, modifications of RNA nucleotides are generally directed by small nucleolar RNAs (snoRNA; 60-300 nt),Wirta W (2006). Mining the transcriptome – methods and applications. ISBN 91-7178-436-5.  found in the nucleolus and 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.Covello PS, Gray MW (1989). "RNA editing in plant mitochondria". Nature 341: 662–66. doi:10.1038/341662a0. Omer AD, Ziesche S, Decatur WA, Fournier MJ, Dennis PP (2003). "RNA-modifying machines in archaea". Molecular Microbiology 48 (3): 617–29. doi:10.1046/j.1365-2958.2003.03483.x. 

List of RNAs

Type	Abbr.	FunctionUnless else specified in boxes, then listing of housekeeping RNAs follows: Szymanski J, Barciszewska MZ, Zywicki M, Barciszewski J (2003). "Noncoding RNA transcripts". J. Appl. Genet. 44 (1): 9. PMID 12590177.	Distribution	Ref.
Messenger RNA	mRNA	Codes for protein	All organisms
Ribosomal RNA	rRNA	Translation	All organisms
Transfer RNA	tRNA	Translation	All organisms
Transfer-messenger RNA	tmRNA	Rescuing stalled ribosomes	Bacteria	Gillet R, Felden B (2001). "Emerging views on tmRNA-mediated protein tagging and ribosome rescue". Molecular Microbiology 42 (4): 879–85. doi:10.1046/j.1365-2958.2001.02701.x.
Antisense RNA	aRNA	Gene regulation	All organisms	Brantl S (2002). "Antisense-RNA regulation and RNA interference". Biochimica et Biophysica Acta 1575 (1–3): 15–25. PMID 12020814.
Small interfering RNA	siRNA	Gene regulation	Most eukaryotes	Ahmad K, Henikoff S (2002). "Epigenetic consequences of nucleosome dynamics". Cell 111 (3): 281–84. doi:10.1016/S0092-8674(02)01081-4.
MicroRNA	miRNA	Gene regulation	Most eukaryotes	Lin S-L, Miller JD, Ying S-Y (2006). "Intronic microRNA (miRNA)". Journal of Biomedicine and Biotechnology: 1–13. PMID 17057362.
trans-acting siRNA	tasiRNA	Gene regulation	Plants (Arabidopsis thaliana)	Vazquez F, Vaucheret H (2004). "Endogenous trans-acting siRNAs regulate the accumulation of Arabidopsis mRNAs". Mol. Cell (16): 1–13. PMID 17057362.
Piwi-interacting RNA	piRNA	Gene regulation	Animals
Small nuclear RNA	snRNA	Various	Eukaryotes and archaea	Thore S, Mayer C, Sauter C, Weeks S, Suck D (2003). "Crystal Structures of the Pyrococcus abyssi Sm Core and Its Complex with RNA". J. Biol. Chem. 278 (2): 1239–47. doi:10.1074/jbc.M207685200.
Small nucleolar RNA	snoRNA	Nucleotide modification of RNAs	Eukaryotes and archaea	Kiss T (2001). "Small nucleolar RNA-guided post-transcriptional modification of cellular RNAs". The EMBO Journal 20: 3617–22. doi:10.1093/emboj/20.14.3617.
Guide RNA	gRNA	mRNA modification	Kinetoplastid mitochondria	Alfonzo JD, Thiemann O, Simpson L (1997). "The mechanism of U insertion/deletion RNA editing in kinetoplastid mitochondria". Nucleic Acids Research 25 (19): 3751–59. PMID 9380494.
Ribonuclease P	RNase P	tRNA maturation	All organisms	Pannucci JA, Haas ES, Hall TA, Harris JK, Brown JW (1999). "RNase P RNAs from some Archaea are catalytically active". Proc Natl Acad Sci USA 96 (14): 7803–08. PMID 10393902.
Ribonuclease MRP	RNase MRP	rRNA maturation, DNA replication	Eukaryotes	Woodhams MD, Stadler PF, Penny D, Collins LJ (2007). "RNase MRP and the RNA processing cascade in the eukaryotic ancestor". BMC Evolutionary Biology 7: S13. doi:10.1186/1471-2148-7-S1-S13.
Y RNA		RNA processing, DNA replication	Animals	Perreault J, Perreault J-P, Boire G (2007). "Ro-associated Y RNAs in metazoans: evolution and diversification". Molecular Biology and Evolution 24 (8): 1678–89. doi:10.1093/molbev/msm084.
Telomerase RNA		Telomere synthesis	Most eukaryotes	Lustig AJ (1999). "Crisis intervention: The role of telomerase". Proc Natl Acad Sci USA 96 (7): 3339–41. PMID 10097039.
Signal recognition particle RNA		Protein export	All organisms	Gribaldo1 S, Brochier-Armanet C (2006). "The origin and evolution of Archaea: a state of the art". Philos Trans R Soc Lond B Biol Sci. 361 (1470): 1007–22. PMID 16754611.
Retrotransposon		Self-propagating	Eukaryotes and some bacteria	Boeke JD (2003). "The unusual phylogenetic distribution of retrotransposons: a hypothesis". Genome Research 13: 1975–83. PMID 12952870.
Viroid		Self-propagating	Infected plants	Flores R, Hernández C, Martínez de Alba AE, Daròs JA, Di Serio F (2005). "Viroids and viroid-host interactions". Annual Review of Phytopathology 43: 117–39. PMID 16078879.
Viral genome		Information carrier	Double-stranded RNA viruses, positive-sense RNA viruses, negative-sense RNA viruses, most satellite viruses and reverse transcribing viruses

Discovery

Nucleic acids were discovered in 1868 by Friedrich Miescher, who called the material \'nuclein\' since it was found in the nucleus.Dahm R (2005). "Friedrich Miescher and the discovery of DNA". Developmental Biology 278 (2): 274–88. PMID 15680349.  It was later discovered that prokaryotic cells, which do not have a nucleus, also contain nucleic acids. The role of RNA in protein synthesis had been suspected since 1939, based on experiments carried out by Torbjörn Caspersson, Jean Brachet and Jack Schultz.Nierhaus KH, Wilson DN (2004). Protein Synthesis and Ribosome Structure. Wiley-VCH, 3. ISBN 3527306382.  Gerard Marbaix isolated the first messenger RNA, for rabbit hemoglobin, and found it induced the synthesis of hemoglobin after injection into oocytes.Carlier M (June 2003). L\'ADN, cette "simple" molécule. Esprit libre. Severo Ochoa won the 1959 Nobel Prize in Medicine after he discovered how RNA is synthesized.Ochoa S (1959). Enzymatic synthesis of ribonucleic acid. Nobel Lecture. The sequence of the 77 nucleotides of a yeast RNA was found by Robert W. Holley in 1965,Holley RW et al (1965). "Structure of a ribonucleic acid". Science 147 (1664): 1462–65. doi:10.1126/science.147.3664.1462.  winning Holley the 1968 Nobel Prize in Medicine. Carl Woese realised RNA can be catalytic in 1967 and proposed the earliest forms of life relied on RNA both to carry genetic information and to catalyze biochemical reactions—an RNA world.Siebert S (2006). Common sequence structure properties and stable regions in RNA secondary structures. Dissertation, Albert-Ludwigs-Universität, Freiburg im Breisgau 1.Szathmáry E (1999). "The origin of the genetic code: amino acids as cofactors in an RNA world". Trends Genet. 15 (6): 223–9. doi:10.1016/S0168-9525(99)01730-8.  In 1976, Walter Fiers and his team at the University of Ghent determined the first complete nucleotide sequence of an RNA virus genome, that of bacteriophage MS2.Fiers W et al (1976). "Complete nucleotide-sequence of bacteriophage MS2-RNA: primary and secondary structure of replicase gene". Nature 260: 500–7. PMID 1264203.  In the early 1990s it was found that introduced genes can silence homologous endogenous genes in plants.Napoli C, Lemieux C, Jorgensen R (1990). "Introduction of a chimeric chalcone synthase gene into petunia results in reversible co-suppression of homologous genes in trans.". Plant Cell 2 (4): 279–89. PMID 12354959.  At about the same time, 22 nt long RNAs, now known as microRNAs, were found to have a role in the development of C. elegans.Ruvkun G (2001). "Glimpses of a tiny RNA world". Science 294 (5543): 797–99. doi:10.1126/science.1066315.  The discovery of gene regulatory RNAs has led to attempts to develop drugs made of RNA, particularly to silence oncogenes and viral genes.Trent RJ (2005). Molecular Medicine, 3rd edition, Elsevier, 160–63. ISBN 0-12-699057-3.  There is no such drug on the market, but there is promising research on using siRNAs to downregulate genes through RNA interference.Fichou Y, Férec C (2006). "The potential of oligonucleotides for therapeutic applications". Trends in Biotechnology 24 (12): 563–70. doi:10.1016/j.tibtech.2006.10.003. 

See also

• Genetics
• Molecular biology
• Phosphoramidite
• Quantification of nucleic acids
• RNA Ontology Consortium
• Sequence profiling tool
• RNA extraction

References

External links

• RNA World website
• Nucleic Acid Database Images of DNA, RNA and complexes.
• RNAJunction Database: Extracted atomic models of RNA junction and kissing loop structures.
• RNAJournal International forum for publishing original reports on RNA research in the broadest sense.

v • d • e Major families of biochemicals
Peptides | Amino acids | Nucleic acids | Carbohydrates | Nucleotide sugars | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides
Analogues of nucleic acids:	Types of nucleic acids	Analogues of nucleic acids:
Nucleobases:	Purine (Adenine, Guanine) | Pyrimidine (Uracil, Thymine, Cytosine)
Nucleosides:	Adenosine/Deoxyadenosine | Guanosine/Deoxyguanosine | Uridine | Thymidine | Cytidine/Deoxycytidine
Nucleotides:	monophosphates (AMP, GMP, UMP, CMP) | diphosphates (ADP, GDP, UDP, CDP) | triphosphates (ATP, GTP, UTP, CTP) | cyclic (cAMP, cGMP, cADPR)
Deoxynucleotides:	monophosphates (dAMP, dGMP, TMP, dCMP) | diphosphates (dADP, dGDP, TDP, dCDP) | triphosphates (dATP, dGTP, TTP, dCTP)
Ribonucleic acids:	RNA | mRNA (pre-mRNA/hnRNA) | tRNA | rRNA | aRNA | gRNA | miRNA | ncRNA | piRNA | shRNA | siRNA | snRNA | snoRNA | tmRNA
Deoxyribonucleic acids:	DNA | cDNA | gDNA | msDNA | mtDNA
Nucleic acid analogues:	GNA | LNA | PNA | TNA | morpholino
Cloning vectors:	phagemid | plasmid | lambda phage | cosmid | P1 phage | fosmid | BAC | YAC | HAC

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