RNA interference (RNAi) is a natural process in cells that uses small RNA molecules to regulate gene expression. Craig Fire and Andrew Mello discovered RNAi in 1998 through their experiments injecting double-stranded RNA into C. elegans worms. They found this silenced or interfered with the expression of genes with complementary RNA sequences. RNAi has important roles in defending against viruses and regulating development, with the small RNAs binding to messenger RNAs to decrease their activity. It has potential applications in gene therapy, functional genomics, agriculture, and more.

1. RNA Interference (RNA i) and
RNA Induced Gene Silencing
By
V.Vigneshwaran
madonscience.blogspot.com ADVANCED MOLECULAR BIOLOGY

2. About RNAi
• RNA interference (RNAi) is a system within living cells that takes part in
controlling which genes are active and how active they are. Two types of
small RNA molecules – microRNA (miRNA) and small interfering RNA
(siRNA) – are central to RNA interference.
• RNAs are the direct products of genes, and these small RNAs can bind to
other specific RNAs (mRNA) and either increase or decrease their activity,
for example by preventing a messenger RNA from producing a protein.
• RNA interference has an important role in defending cells against parasitic
genes – viruses and transposons – but also in directing development as
well as gene expression in general.

3. Discovery
• In an attempt to alter flower colors in petunias, researchers introduced additional copies
of a gene encoding chalcone synthase, a key enzyme for flower pigmentation into petunia
plants of normally pink or violet flower color. The overexpressed gene was expected to
result in darker flowers, but instead produced less pigmented, fully or partially white
flowers, indicating that the activity of chalcone synthase had been substantially decreased;
in fact, both the endogenous genes and the transgen
• This phenomenon was called co-suppression of gene expression, but the molecular
mechanism remained unknown.
• While it was known that plants expressing virus-specific proteins showed enhanced
tolerance or resistance to viral infection, it was not expected that plants carrying only
short, non-coding regions of viral RNA sequences would show similar levels of protection.
• Craig C. Mello and Andrew Fire’s 1998 Nature paper reported a potent gene silencing
effect after injecting double stranded RNA into C. elegans. In investigating the regulation of
muscle protein production, they observed that neither mRNA nor antisense RNA injections
had an effect on protein production, but double-stranded RNA successfully silenced the
targeted gene. As a result of this work, they coined the term RNAi.

4. RNAi have Won Nobel
Craig C. Mello Andrew Fire

5. RNAi Induced Gene Silencing
in Petunia Plants

8. The Mechanism of RNA Interference
 The long dsRNAs enter a cellular pathway that is
commonly referred to as the RNA interference
(RNAi) pathway.
 First, the dsRNAs get processed into 20-25
nucleotide (nt) small interfering RNAs (siRNAs)
by an RNase III-like enzyme called Dicer.
 Then, the siRNAs assemble into
endoribonuclease-containing complexes known as
RNA-induced silencing complexes (RISCs),
unwinding in the process.
 The siRNA strands subsequently guide the RISCs
to complementary RNA molecules, where they
cleave and destroy the cognate RNA (
 Cleavage of cognate RNA takes place near the
middle of the region bound by the siRNA strand.

10. Biological Functions Of RNAi
Immunity
Downregulation of genes
Upregulation of genes

11. Applications
• Gene knockdown
• Functional genomics
• Medicine
• Biotechnology

12. Role of iRNA in Biotechnology…
 RNA interference has been used for applications in biotechnology, particularly
in the engineering of food plants that produce lower levels of natural plant
toxins.
 For example, cotton seeds are rich in dietary protein but naturally contain the
toxic terpenoid product gossypol, making them unsuitable for human
consumption.
 RNAi has been used to produce cotton stocks whose seeds contain reduced
levels of delta-cadinene synthase, a key enzyme in gossypol production,
without affecting the enzyme's production in other parts of the plant, where
gossypol is important in preventing damage from plant pests.
 Similar efforts have been directed toward the reduction of the cyanogenic
natural product linamarin in cassava plants

13. Role of iRNA in Medicine…
 It may be possible to exploit RNA interference in therapy.
 A key area of research in the use of RNAi for clinical applications is the
development of a safe delivery method, which to date has involved mainly
viral vector systems similar to those suggested for gene therapy
 Potential treatments for neurodegenerative diseases have also been
proposed, with particular attention being paid to the polyglutamine diseases
such as Huntington's disease.
 RNA interference is also often seen as a promising way to treat cancer by
silencing genes differentially upregulated in tumor cells or genes involved
in cell division.

14. Conclusion
There are many things on the horizon that Dicer and its
RNAi mechanism may be able to accomplish for us.
ds RNA-based vaccines and/or treatments for viral infections,
perhaps including HIV.
Gene silencing of genes in cancer cells.
Treatment of genetic diseases?
More fantastic instances of viral resistance engineered into
crops.

15. References
http://www.ambion.com/techlib/append/RNAi_mechanism.html
http://en.wikipedia.org/wiki/RNA_interference
http://en.wikipedia.org/wiki/RNA-induced_silencing_complex
http://www.gene-quantification.de/rnai.html
http://www.uni-konstanz.de/FuF/chemie/jhartig/
NOTE: ALL THE IMAGES THAT WERE USED IN THIS POWER POINT
SLIDES WERE DOWNLOADED FROM THE GOOGLE IMAGES.

17. AUTHOR INFORMATION
By Vigneshwaran V.
PhD Scholar, Kuvempu University, INDIA
Follow me at,
https://twitter.com/vvigneshwaran14
https://www.facebook.com/vignesh.waran.7731247
Mail to,
vikkku@yahoo.com
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