RNAi

[aftabac]

RNAi technology based on Double stranded RNA or dsRNA, who naturally dsRNA is encoded in the genome, is it possible other then shRNA.
I hope you will answer.


waiting

Aftab ahmad chatha
[Only registered users see links. ]

[Polyzoom]

I know there are:

miRNA - micro-RNA, a form of ss single-stranded RNA typically 20-25 nucleotides

shRNA - short hairpin RNA (double stranded in hairpin elements)

siRNA - siRNA have short around 20-nucleotide double-strand of RNA (dsRNA) with 2-nt 3' overhangs

shRNA = siRNA they are the same I believe

(RNAi molecules)

miRNA, siRNA, and shRNA are all found in humans. I am not sure about any newer forms of inhibitory RNA molecules.

[Polyzoom]

oh there are also larger dsRNAs which are precursor molecules to siRNA / shRNAs

[aftabac]

yes all these RNA forms are present in the human, but i want to know how these dsRNA are encoded by the genome. or how these are formed in humans.

aftab

[admin]

Here is a nature review paper on RNAi

http://www.nature.com/nature/journal...C32422287EA5DE

Figure 1 | RNAi-mediated gene silencing.
RNA interference (RNAi) is an apparently ancient defence mechanism against foreign double-stranded RNA (dsRNA). RNAs of just 22 nucleotides in length, called small interfering RNAs (siRNAs), are snipped from longer dsRNA chains by an enzyme called Dicer. The antisense strand of the siRNA is used by an RNA-induced silencing complex (RISC) to guide messenger RNA (mRNA) cleavage, so promoting mRNA degradation.
Modified with permission from McManus, M. T. & Sharp, P. A. Gene silencing in mammals by small interfering RNAs. Nature Rev. Genet. 3, 737-747 (2002) © Macmillian Magazines Ltd. miRNA, microRNA; stRNA, small temporal RNA.
[IMG]file:///E:/DOCUME%7E1/GUS%7E1.GUS/LOCALS%7E1/Temp/moz-screenshot.jpg[/IMG][IMG]file:///E:/DOCUME%7E1/GUS%7E1.GUS/LOCALS%7E1/Temp/moz-screenshot-1.jpg[/IMG][IMG]file:///E:/DOCUME%7E1/GUS%7E1.GUS/LOCALS%7E1/Temp/moz-screenshot-2.jpg[/IMG]http://www.nature.com/horizon/rna/ba...ference_f1.jpg

Interestingly, the human siRNAs are there to protect against dsRNAs from viruses, however they THEMSELVES are first dsRNAs to begin with...



Some Interesting Articles in:
Specific inhibition of gene expression by small double-stranded RNAs in invertebrate and vertebrate systems

Natasha J. Caplen*,, Susan Parrish,§, Farhad Imani¶, Andrew Fire, and Richard A. Morgan*,
PNAS | August 14, 2001 | vol. 98 | no. 17 | 9742-9747

Short interfering RNAs (siRNAs) are double-stranded RNAs of 21-25 nucleotides that have been shown to function as key intermediaries in triggering sequence-specific RNA degradation during posttranscriptional gene silencing in plants and RNA interference in invertebrates. siRNAs have a characteristic structure, with 5'-phosphate/3'-hydroxyl ends and a 2-base 3' overhang on each strand of the duplex. In this study, we present data that synthetic siRNAs can induce gene-specific inhibition of expression in Caenorhabditis elegans and in cell lines from humans and mice. In each case, the interference by siRNAs was superior to the inhibition of gene expression mediated by single-stranded antisense oligonucleotides. The siRNAs seem to avoid the well documented nonspecific effects triggered by longer double-stranded RNAs in mammalian cells. These observations may open a path toward the use of siRNAs as a reverse genetic and therapeutic tool in mammalian cells.