RNAa
Encyclopedia
Small double-stranded RNA (dsRNA) has been found to silence gene expression by an evolutionally conserved mechanism known as RNA interference
or RNAi
. Such dsRNAs are called small interfering RNAs or siRNA
. RNAi can occur at both transcriptional and post-transcriptional levels. Surprisingly, two recent studies have found that dsRNA can also activate gene expression, a mechanism that has been termed "small RNA-induced gene activation" or RNAa. It has been shown that dsRNAs targeting gene promoters induce potent transcriptional activation of associated genes. Both studies demonstrate RNAa in human cells using synthetic dsRNAs termed small activating RNAs (saRNA
s). Endogenous miRNA that cause RNAa has also been found in humans. Very recently, RNAa has been demonstrated in several mammalian species other than human including non-human primates, mouse and rat, suggesting that RNAa is a general gene regulation mechanism conserved at least in mammals. It is likely that RNAa also exists in other organisms.
Another surprising observation is that gene activation by RNAa is long-lasting. Induction of gene expression has been seen to last for over ten days. The prolonged effect of RNAa could be attributed to epigenetic changes at dsRNA target sites.
RNA interference
RNA interference is a process within living cells that moderates the activity of their genes. Historically, it was known by other names, including co-suppression, post transcriptional gene silencing , and quelling. Only after these apparently unrelated processes were fully understood did it become...
or RNAi
RNAI
RNAI is a non-coding RNA that is an antisense repressor of the replication of some E. coli plasmids, including ColE1. Plasmid replication is usually initiated by RNAII, which acts as a primer by binding to its template DNA. The complementary RNAI binds RNAII prohibiting it from its initiation role...
. Such dsRNAs are called small interfering RNAs or siRNA
Sírna
Sírna Sáeglach , son of Dian mac Demal, son of Demal mac Rothechtaid, son of Rothechtaid mac Main, was, according to medieval Irish legend and historical tradition, a High King of Ireland...
. RNAi can occur at both transcriptional and post-transcriptional levels. Surprisingly, two recent studies have found that dsRNA can also activate gene expression, a mechanism that has been termed "small RNA-induced gene activation" or RNAa. It has been shown that dsRNAs targeting gene promoters induce potent transcriptional activation of associated genes. Both studies demonstrate RNAa in human cells using synthetic dsRNAs termed small activating RNAs (saRNA
SaRNA
Small activating RNA molecules can induce target gene expression in a phenomenon referred to as dsRNA-induced transcriptional activation ....
s). Endogenous miRNA that cause RNAa has also been found in humans. Very recently, RNAa has been demonstrated in several mammalian species other than human including non-human primates, mouse and rat, suggesting that RNAa is a general gene regulation mechanism conserved at least in mammals. It is likely that RNAa also exists in other organisms.
Another surprising observation is that gene activation by RNAa is long-lasting. Induction of gene expression has been seen to last for over ten days. The prolonged effect of RNAa could be attributed to epigenetic changes at dsRNA target sites.
External links
- RNAa FAQs Li Lab, University of California San Francisco
- How to get your genes switched on. New Scientist 16 November 2006