Courtesy of Sirna Therapeutics
RNA interference (RNAi) is a type of posttranscriptional genetic regulation that occurs naturally in the cytoplasm to protect the cell against excess and foreign RNAs. Double-stranded RNA (dsRNA), an unusual type of nucleic acid encoded in viral genomes and transposable elements, triggers a process that regulates gene expression without touching the genome.
Scientists know that RNAi protects the cell against viral infections and genomic instability, but no one knows exactly how dsRNA triggers RNAi's defense mechanism. Scientists do know the chain of events that the dsRNA initiates, which ultimately rids the cell of mRNA.
Dicers, a class of RNase III enzymes, recognize dsRNA molecules and cut them into short (~21–25) nucleotide segments called small interfering RNAs (siRNAs). These segments hook up with an RNA-induced silencing complex (RISC), and together they hunt for homologous mRNA substrates, which they then degrade, effectively silencing gene expression.
So far, researchers ...
