RNAi at a Glance

RNAi is a type of gene therapy that “silences” genes by disrupting the protein-making process. That process is essentially explained in a statement which scientists have dubbed the “central dogma of molecular biology”: DNA makes RNA makes proteins.

DNA lives in the cell nucleus and consists of thousands of genes, each one holding the code, or “blueprint,” for building a particular protein molecule and thus ensuring a certain cell function performed by that protein. (Proteins carry out virtually every cell function, including the activation of other genes.) When a specific protein is needed by the body, its genetic code is copied from DNA; the “copy” is a single molecular strand known as messenger RNA (mRNA). This process, known as transcription, takes place in the cell nucleus.

But proteins are manufactured outside the cell nucleus, in microscopic structures called ribosomes. The mRNA is the vital link: the “courier” that picks up the protein-making instructions from DNA and delivers them to the protein-producing ribosomes.

RNA interference involves introducing miRNAs or siRNAs to a cell where they target, bind to and destroy specific mRNAs—effectively shutting down production of particular proteins and whatever gene expression they trigger or suppress.


RNA—the acronym for ribonucleic acid, one of two nucleic acids found in the cells of every organism (the other is deoxyribonucleic acid, or DNA). RNA is composed of tiny molecules called nucleotides that are arranged in a chain. RNA transports the information needed to make proteins.

non-coding RNA (ncRNA)—a functional RNA molecule that is not translated into a protein. Examples of ncRNAs are short interfering RNAs and microRNAs.

short interfering RNAs (siRNAs)—small, double-stranded molecules that are used in RNA interference to prevent the translation of genes into proteins. siRNAs also are called small interfering RNAs or silencing RNAs.

microRNAs (miRNA)—small, hairpin-like structures of single-stranded RNA molecules that can regulate the expression of protein-coding genes.

RNA interference (RNAi)—a revolutionary technique for gene silencing. In this technique, RNA is introduced into a cell to disrupt messenger RNA and prevent it from being translated into a protein.