RNA silencing is remarkable type of gene regulation
From today, I will collect any references about RNA silencing. RNA silencing is a remarkable type of gene regulation based on sequence-specific targeting and degradation of RNA. The term encompasses related pathways found in a broad range of eukaryotic organisms, including fungi, plants, and animals. In plants, it serves as an antiviral defense, and many plant viruses encode suppressors of silencing. The emerging view is that RNA silencing is part of a sophisticated network of interconnected pathways for cellular defense, RNA surveillance, and development and that it may become a powerful tool to manipulate gene expression experimentally.
RNA silencing was first discovered in transgenic plants, where it was termed cosuppression or posttranscriptional gene silencing(PTGS). Sequence-specific RNA degradation processes related to PTGS have also been found in ciliates, fungi (quelling), and a variety of animals from Caenorhabditis elegans to mice (RNA interference RNAs (siRNAs)). A key feature uniting the RNA silencing pathways in different organisms is the importance of double-stranded RNA (dsRNA) as a trigger or an intermediate. The dsRNA is cleaved into small interfering RNAs (siRNAs) (21 to 25 nucleotides) of
both polarities, and these are thought to act as guides to direct the RNA degradation machinery to the target RNAs. An intriguing aspect of RNA silencing in plants is that it can be triggered locally and then spread via
a mobile silencing signal. The signaling molecule is currently unknown but is
expected to contain a nucleic acid component to account for the sequence-specificity. Systemic spread of silencing also occurs in other organisms, though the mechanism may not be the same as in plants. Finally, in plants, RNA silencing is correlated with methylation of homologous transgene DNA in the nucleus. Other types of epigenetic modifications may be associated with silencing in other organisms.
Three major avenues of research have contributed to a recent burst of information about these different aspects of RNA silencing.
- Mutant analyses have identified a number of genes that are required for RNA silencing in multiple organisms.
- Plant viral suppressors of silencing have provided a tool to identify steps in the pathway and an alternate approach to find cellular proteins that are involved in the process.
- The development of an in vitro RNA silencing system from Drosophila has allowed a biochemical analysis of some steps in the pathway.
