Antisense RNA

Antisense RNA (aRNA) is single-stranded RNA that is complementary to a messenger RNA (mRNA) strand transcribed within a cell. Antisense RNA may be introduced into a cell to inhibit translation of a complementary mRNA by base pairing to it and physically obstructing the translation machinery. This effect is therefore stoichiometric. An example of naturally occurring mRNA antisense mechanism is the hok/sok system of the E.coli R1 plasmid. Antisense RNA has long been thought of as a promising technique for disease therapy; the only such case to have reached the market is the drug fomivirsen. One commentator has characterized antisense RNA as one of "dozens of technologies that are gorgeous in concept, but exasperating in [commercialization] ".Citation
last=DePalma |first=Angelo |date=August 2005 |title=Twenty-Five Years of Biotech Trends
periodical=Genetic Engineering News |publisher=Mary Ann Liebert |volume=25 |issue=14 |pages=1, 14–23
url=http://www.genengnews.com/articles/chitem.aspx?aid=1005&chid=0 |accessdate=2008-08-17 |issn=1935-472X] Generally, antisense RNA still lack effective design, biological activity, and efficient route of administration. [ [http://mct.aacrjournals.org/cgi/content/full/1/5/347 Antisense Oligonucleotides: Basic Concepts and Mechanisms] Nathalie Dias and C. A. Stein. Columbia University, New York, New York 10032 ]

Historically, the effects of antisense RNA have often been confused with the effects of RNA interference, a related process in which double-stranded RNA fragments called small interfering RNAs trigger catalytically mediated gene silencing, most typically by targeting the RNA-induced silencing complex (RISC) to bind to and degrade the mRNA. Attempts to genetically engineer transgenic plants to express antisense RNA instead activate the RNAi pathway, although the processes result in differing magnitudes of the same downstream effect, gene silencing. Well-known examples include the Flavr Savr tomato and two cultivars of ringspot-resistant papaya. Sanders RA, Hiatt W. (2005). Tomato transgene structure and silencing. "Nat Biotechnol" 23(3):287-9. PMID 15765076] Chiang C, Wang J, Jan F, Yeh S, Gonsalves D (2001). "Comparative reactions of recombinant papaya ringspot viruses with chimeric coat protein (CP) genes and wild-type viruses on CP-transgenic papaya". "J Gen Virol" Pt 11): 2827-36. PMID 11602796]

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