Biochemistry 4122004

9 April Lecture

RNA Interference (RNAi)(see also siRNA, micRNA, stRNA, etc.)

The Discovery of the RNA Interference (RNAi) Phenomenon

1. Gene-specific inhibition of expression by anti-sense nucleic acids was discovered in the 1980’s (Inouye, 1988).

2. Guo and Kemphues (1995) showed that, in some cases for C. elegansgenes, the sense strand inhibited just as well as the anti-sense strand (!? - why careful controls are always wise!).

3. Three years later, Mello and Fire (1998) tested whether both the senseand the anti-sense strand together would inhibit or cancel other out. They hit the jackpot: the dsRNA that they inadvertently created inhibited homologous mRNA expression much more strongly than either the sense or the anti-sense strands alone (!!??).

>>> RNAi may be a very ancient defense mechanism that evolved ineukaryotic organisms to protect their cells against viruses.

Tijsterman et al (2002) Annu. Rev. Genet. 36, 489.

Tijsterman et al (2002) Annu. Rev. Genet. 36, 489.

Micro-RNAs (e.g., so-called stRNAs) are also involved in endogenous gene regulation

Grosshans & Slack (2002). J. Cell Biol. 156, 17.

Short RNAs regulate gene expression by different mechanisms, but use some of the same cellular machinery (e.g., Dicer) to do it.

Moss (2001) Curr. Biol. 11, R772.

Kapranov et al (2002) Science 296, 916.

RNAi “Knockdown” Experiments are Very Useful for Studying the Functions of Genes In Vivo

Hannon (2002) Nature 418, 244.

Transitive RNAi - “Spreading” of Silencing

Hannon (2002) Nature 418, 244.

Stevenson (2003) Nature Reviews 3, 851.

Carpenter & Sabatini (2004)