ABSTRACT
RNA silencing, also known as posttranscriptional gene silencing (PTGS) or RNA interference (RNAi), is an epigenetic form of RNA degradation believed to be an important defense against foreign nucleic acids that is widely used as a tool for inactivating gene expression.1-3 It is now recognized that RNA silencing occurs in a wide variety of organisms. Examples include transgene-induced PTGS in plants, quelling in Neurospora Crassa, and RNA interference (RNAi) mediated by double-stranded RNA (dsRNA) or 21-to 22-nt small interfering RNAs (siRNA) in Caenorhabditis Elegans, Drosophila Melanogaster, and mammalian cells. Considerable evidence suggests that the core mechanism has been highly conserved in evolution.
