Detection of long and short double-stranded RNAs

In RNA interference (RNAi), long double-stranded RNAs (dsRNAs) of more than 100 nucleotides (nt) are diced into short dsRNAs (small interfering RNAs, siRNAs) of about 21-24 nt, the guide strand of which is incorporated into the RNA-induced silencing complex (RISC) that slices a specific mRNA. Consequently viral dsRNAs are known as potent inducers for RNAi, which probably originated from a defense mechanism against nucleic acid parasites. Therefore detection of long and short dsRNAs must be crucial techniques for RNAi or virus research. The methods for simple and sensitive detection of short dsRNAs (siRNAs) by northern hybridization, isolation of long dsRNAs by CF-11 cellulose chromatography, and detection of long dsRNAs by agarose gel electrophoresis and northern hybridization are described here.