Old threads on "siRNA, microRNA and RNAi" are achived here - (Feb/03/2009 )
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?
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.
These might also help.
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.
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