RNA i Glossary

Dicer - Dicer is a member of the RNase III family of nucleases that specifically cleave double-stranded RNA s. Dicer processes long dsRNA into siRNA of 21-23 nt.

Interferon - A small and highly potent molecule that functions in an autocrine and paracrine manner, and that induces cells to resist viral replication. This term is related to RNA i/Index.shtml">RNA i because in mammals introduction of dsRNA longer than 30 nt induces a sequence-nonspecific interferon response.

Micro-RNA - Micro-RNA s (miRNA ) are single-stranded RNA s of 22-nt that are processed from ~70-nt hairpin RNA precursors by Rnase III nuclease Dicer. Similar to siRNA s, miRNA s can silence gene activity via destruction of homologous mRNA in plants or blocking its translation in plants and animals.

Post-Transcriptional Gene Silencing - Post-transcriptional gene silencing (PTGS) is a sequence-specific RNA degradation system designed to act as an anti-viral defense mechanism. A form of PTGS triggered by transgenic DNA, called co-suppression, was initially described in plants and a related phenomenon, termed quelling, was later observed in the filamentous fungus Neurospora crassa

Ribozyme - Ribozymes are RNA molecules that act as enzymes in the absence of proteins.

RNA Interference - RNA Interference (RNA i), a term coined by Fire et al in 1998, is a phenomenon that small double-stranded RNA (referred as small interference RNA or siRNA ) can induce efficient sequence-specific silence of gene expression.

RNA -Directed DNA Methylation - RNA -directed DNA methylation (RdDM) is an RNA directed silencing mechanism found in plants. Similar to RNA interference (RNA i), RdDM requires a double-strand RNA that is cut into short 21-26-nt fragments. DNA sequences homologous to these short RNA s are then methylated and silenced.

RNA -Induced Silencing Complex - RNA -induced silencing complex (RISC) is an siRNA -directed endonuclease, catalyzing cleavage of a single phosphodiester bond on the RNA target.

RNA i Trigger - RNA i triggers are double-stranded RNA s containing 21-23 nt sense and antisens strands hybridized to have 2 nt overhangs at both 3' ends.

Small Interfering RNA - Small Interfering RNA (siRNA ) is 21-23-nt double-strand RNA . It guides the cleavage and degradation of its cognate RNA .