"This article is about a new genetic discovery on how we can control diseases, disorders and health in humans."  

Our early understanding of human diseases began with the 1993 mapping of the human genome that included DNA and RNA.  But it is only since 2004 that the impact RNA has on diseases and health became clearer with the discoveries that the original RNA is accompanied by smaller RNA genes referred to as RNA interference or RNAi.  RNA can switch certain genes and control other genes that affect diseases and health.   Ghildiyal: RNA types & functions 2009

RNA interference (RNAi) is a system within living cells that takes part in controlling which genes are active and how active they are.  Eggleston: RNA silencing 2009  Ghildiyal: RNA types & functions 2009

The information about how RNA genes work is difficult to understand for most of us.  The two videos that follow simplify how RNA i  genes  work.

The first video introduces the early discovery of Robert Krulwich's petunia accidental discovery of RNAi switching genes off and on to control characteristics and functions of a flower. He identified RNAi as the switch that all organisms have for turning body systems on or off.  This new information has implications for applying this new knowledge to plants and animals.  RNAi may help us reset the controls for normalized body functions such as the immune and metabolic systems as well as preventing diseases and disorders.   

RNAi video #1

The second video continues from the first video:

RNAi gene video # 2

Now that you have viewed the two videos and became more informed about RNA, you are ready for more complexity about RNA.  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.

The illustration on the left  [ source Dellavedova ] illustrates how RNAi works.   RNAi can defend against parasitic genes and viruses that can cause diseases or disorders. RNAi can recognize and inactivate certain functions of a plant or animal.  It does so by a DNA strand of the gene, a transposon, being able to jump and insert itself into a new location in the strand.  Such relocation is the genome switch to turn on or off the behavior of the original gene.   Most of the transposons in the genome are stably silenced and many of them have been “tamed” and do important cellular jobs.  But mother nature has also endowed genes with the ability to change the script for life. 

Medical Applications:  "It may be possible to exploit RNA interference in therapy. It is the Transposons, which are pieces of DNA that can “jump” into novel positions in the genome, that can make this possible.  They can insert themselves into DNA without requiring any similar sequence to be present in themselves and their “target”. This makes them powerful mutagens that can cause mutations and even diseases in humans. 

Although it is difficult to introduce long dsRNA strands into mammalian cells due to the interferon response, the use of short interfering RNA mimics has been more successful.  Among the first applications to reach clinical trials were in the treatment of macular degeneration and respiratory syncytial virus, RNAi has also been shown to be effective in the reversal of induced liver failure in mouse models.

"Other proposed clinical uses center on antiviral therapies, including topical microbicide treatments that use RNAi to treat infection by herpes simplex virus type 2 and the inhibition of viral gene expression in cancerous cells [at Harvard University Medical School; in mice, so far], knockdown of host receptors and coreceptors for HIV, the silencing of hepatitis A and hepatitis B genes, silencing of influenza gene expression, and inhibition of measles viral replication. 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 up-regulated in tumor cells or genes involved in cell division."  Wiki: RNAi

Post-transcriptional gene silencing (PTGS), which was initially considered a bizarre phenomenon limited to petunias and a few other plant species, is now one of the hottest topics in molecular biology. In the last few years, it has become clear that PTGS occurs in both plants and animals and has roles in viral defense and transposon silencing mechanisms. 

Flash animation 2001 Hammond: animation RNAi   of "How Does RNAi Work?" 

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