Antisense RNA is a single-stranded RNA that is complementary to a messenger RNA 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. Antisense RNA has long been thought of as a promising technique for disease therapy, but generally still lacks effective design, biological activity, and efficient routes of administration. Transcription of long antisense non-coding RNAs is a common phenomenon in the mammalian transcriptome and can result in transcriptional gene silencing through histone modifications and creating a heterochromatin environment around the gene. Antisense RNA plays a pivotal role in inhibiting cell translation by producing a

1. BY SREEREMYA.S
M.phil

2. Antisense RNA (asRNA) is a single-stranded
RNA that is complementary to a messenger
RNA (mRNA) strand transcribed within a cell.
Some authors have used the term micRNA
(mRNA-interfering complementary RNA) to
refer to these RNAs but it is not widely used
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

3. . 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]"

4. Generally, antisense RNA still lack effective
design, biological activity, and efficient route
of administration.
Historically, the effects of antisense RNA
have often been confused with the effects of
RNA interference (RNAi), 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.

5. 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.

6. Transcription of longer cis-antisense
transcripts is a common phenomenon in the
mammalian transcriptome
Although the function of some cases have
been described, such as the Zeb2/Sip1
antisense RNA, no general function has been
elucidated. In the case of Zeb2/Sip1, the
antisense noncoding RNA is opposite the 5'
splice site of an intron in the 5'UTR of the
Zeb2 mRNA. Expression of the antisense
ncRNA prevents splicing of an intron that
contains a ribosome entry site necessary for
efficient expression of the Zeb2 protein.

7. Transcriptional gene silencing is the result of
histone modifications, creating an
environment of heterochromatin around a
gene that makes it inaccessible to
transcriptional machinery (RNA polymerase,
transcription factors, etc.).

8. Transcription of long antisense ncRNAs is
often concordant with the associated
protein-coding gene, but more detailed
studies have revealed that the relative
expression patterns of the mRNA and
antisense ncRNA are complex.

9. Transcriptional Gene Silencing:
Genomic Imprinting
Paramutation
Transposon silencing
Transgene silencing
Transcriptional gene silencing

10. Thus antisense RNA can be majourly used in
major molecular analysis
To inhibit the cell translation an antisense
RNA has a pivotal role to play
Since antisense RNA produces complementary
strand to mRNA it is used in specific
inhibition process

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