RNAi is a way to silence genes

Scientists have discovered something called RNA interference (RNAi), which is a process that kills the mRNA, and thus turns genes off. When RNA interference kills the mRNA, no protein can be made.

RNA interference was first described in in plants. Plants that had been invaded by viruses quickly established resistance to the virus within a few days of infection. This is because the plants used RNAi to kill the virus.

Early in an infection, many viruses have two RNA strands, and later in the infection one of these double-strands is used as a mRNA. This double-stranded RNA is the trigger for RNAi. The cell quickly recognizes the double-stranded RNA, and a scissor-like protein called Dicer attaches to it and "dices" it into small pieces.

The small pieces of double-stranded RNA are called short interfering RNAs (siRNA), and together with other proteins, find mRNA in the cell and slice it up. The process is very specific. The small pieces of RNA stick only to mRNA carrying blueprints of its own gene. This will allow only the viral RNA to be destroyed.

Researchers have reported RNA interference in human cells grown in a lab dish and in live mice. Scientists hope that RNA interference might one day be used for medical treatment, such as combating the AIDS virus or influenza virus.

In this model, the proteins Dicer is shown "dicing" a long double-stranded (dsRNA) into small pieces called short-interfering RNAs (siRNAs). One strand of these siRNAs is used by the RNAi Silencing Complex to target and destroy a specific gene (mRNA). Our efforts are focused on studying how RNAi works in mammals such as mice and humans. Exactly how mammalian RNAi works is a mystery. Many proteins are probably involved, and knowing their identities will help unravel the mystery of RNAi.