Old threads on "siRNA, microRNA and RNAi" are achived here - (Feb/04/2009 )

http://www.protocol-online.org/biology-for...roRNA-and-RNAi/

-bioforum-

I am quite confused about the differences between the mechanisms by which (i) antisense oligonucleotides, (ii) long dsRNA, and (iii) short 21-23 dsRNA act on RNAs to affect gene expression in human cells.

I heard that long piece of dsRNA (in both worms or plants) activate the RNAi pathway, in where the long dsRNA gets cleaved into siRNA (20-25nt) and ultimately cause SPECIFIC mRNA degradation via RISC. Does this mean I should talk about the exogenous siRNA here? But long dsRNA cause broad/global effect!! I am confused...

In addition, both siRNA and miRNA are in definition a size of 19-25nt, where both have larger sized precursors. I do need clarification on these definitions. In addtion, isn't miRNA as a definition a endogenous single-stranded RNA?

-1009-

Hi, Your questions are really broad. I hope these links will at-least help you to find the answer. Yes, you are right, miRNA is endogenous single stranded RNA.

http://www.ncbi.nlm....pubmed/19389436

http://www.gene-quan...si-rna-2006.pdf

http://www.nature.co...rnai/index.html

Good luck

-ravibiosciences-

These might also help.

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Kole R, Krainer AR, Altman S. RNA therapeutics: beyond RNA interference and antisense oligonucleotides. Nat Rev Drug Discov. 2012 Jan 20. doi: 10.1038/nrd3625.

http://www.nature.com/nrd/journal/vaop/ncurrent/full/nrd3625.html

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Summerton J. Morpholino, siRNA, and S-DNA Compared: Impact of Structure and Mechanism of Action on Off-Target Effects and Sequence Specificity. Med Chem. 2007;7(7):651-660
http://www.benthamdirect.org/pages/content.php?CTMC/2007/00000007/00000007/0003R.SGM

-Jon Moulton-