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Antisense RNA is a single-stranded RNA that is
complementary to a messenger RNA (mRNA) strand
transcribed within a cell
Antisense RNA introduced into a cell to inhibit
translation of a complementary mRNA by base
pairing to it and creating barrier to the translation
hok/sok system of the E. coli R1 plasmid.
This translational arrest causes reduced amount of
Well-known examples of GM plants produced by
The Flavr Savr tomato ,
Two cultivars of ring spot-resistant papaya.
After 45 days….
Diff. between antisense
technology & RNAi
The intended effect in both will be same i.e. gene
silencing but the processing is little but different.
Antisense technology degrades RNA by enzymes
RNaseH while RNAi employed the enzyme DICER
to degrade the m RNA.
RNAi are twice larger than the antisense
First time at “ free university of Amsterdam”, used
antisense RNA technology against the gene
determining flower color of petunia .
Antisense effect first demonstrated by zemencnick &
Stephenson in 1970 on “Rous sarcoma virus”.
First time antisense oligonucleotides are synthesized
by Eckstein and colleagues.
In 1995 Guo and Kemp hues:
injection of either antisense or sense RNAs in the
germ line of C. elegans was equally effective at
silencing homologous target genes.
Nature’s antisense system
There is HOK(host killing)/SOK(suppress killing) system
in R1 plasmid in E.Coli.
when E. coli cell undergoes division , daughter cell inherit
hok gene & sok gene from parent. But due to short life of
cell, the sok gene is get degraded. So in normal cell, hok
gene get over expressed & cell get die.
But when R1 plasmid is get inherited , it having the sok
gene & sok promoter.
Then it transcripts sok gene & it is get overexpressed
against hok gene.
In this technique, Short segments of single stranded
RNA are introduced.
These oligonucleotides are complementary to the
mRNA, which physically bind to the mRNA.
So , they block the expression of particular gene.
In case of viruses, antisense oligonucleotides inhibit
viral replication with blocking expression of
integrated proviral genes.
Usually consist of 15–20 nucleotides.
Translation of mRNA may be blocked by two
possible mechanisms , These are:-
1] by base specific hybridization – which prevents
access by translation machinery i.e. “hybridization
2] by forming RNA/DNA duplex which is
recognized by nuclease RNaseH , specific for digesting
RNA in an RNA/DNA duplex.
RNaseH is a non-specific endonuclease, catalyzes the
cleavage of RNA via hydrolytic mechanism.
RNaseH has ribonuclease activity cleaves the 3’-O-P
bond of RNA in a DNA/RNA duplex.
Unique DNA sequence
Efficient cellular uptake
Minimal nonspecific binding
Target specific hybridization
Non-toxic antisense construct
Characteristics of antisense
The antisense technology can be modified in THREE
modes because of chemical modifications of the
These modes are due to activation of RNaseH &
internucleotides linkages which do not activate
The antisense oligonucleotides binds the target
sequence causing both “hybridisation arrest ” &
Degradation of mRNA by RNaseH results into
release of oligonucleotides.
They may bind to other copies of target mRNA.
These oligonucleotides are also susceptible to other
This a major parameter affecting catalytic mode of
In this, antisense oligonucleotides binds to target
sequence result in translation arrest but they do not
activate enzyme RNaseH.
Oligoribonucleotides & there analogues ,
oligodeoxyribonucleotides , various non phosphate
& phosphate internucleotides linkages fall in this
They show resistance against nucleuses enzyme and
never get degraded by them.
They also show effective translational arrest .
But the major problem is that they are generally
required higher molar concentrations than those
which activate RNaseH.
It combines features of both previous approaches.
They contains both internucleotides linkages which
are responsible for RNaseH activation & which
shows resistance against them.
Digestion of mRNA target in RNA-DNA duplex
releases oligonucleotides which are resistance
against nuclease enzyme, hence are more effective
than oligonucleotides in 1st approach.
They may form hybrids of
oligodeoxyribonucleotides & Oligoribonucleotides.
The antiviral activity of an antisense oligonucleotides
depends usually on specific binding to a target
Thomas and coworkers coined the term ‘ribozymes’.
These are RNA molecules which have catalytic
activity which degrade nucleotides .
Ribozyme Bind to the target RNA moiety and
inactivate it by cleaving the phosphodiester
backbone at a specific cutting site.
Ribozyme destroy RNA that carries the massage of
These are effectively used against HIV virus.
1. Flavr Savr tomato-antisense
RNA used against an enzyme
polygalacturonase, an softening enzyme which is responsible
2. Transgenic ACMV-resistant cassava plants* –
Used against African cassava mosaic virus
(ACMV) which causes cassava mosaic disease causing major
economic loss in Africa.
the first antiviral drug developed against CMV.
Antisense technology shows potential for diverse
application to field of basic research & therapy.
One of the most approved approaches for inactivating a
single specific gene.
But it may sometime give undesirable effect.
Generally , antisense RNA still lack effective design,
biological activity, and efficient route of administration.
Antisense technologies form a very powerful weapon for
studying gene function and for discovering more specific
treatments of disease.
Attempts are made to genetically engineer transgenic
plants to express antisense RNA instead activate the
RNAi pathway, although the processes result in
A textbook of biotechnology 2nd edition by H. D.
www.ncbi.nlm.nih.com (PubMed ID 17173627)*