Heterologous expression of plant virus genes that suppress post-transcriptional gene silencing results in suppression of RNA interference in Drosophila cells.
BACKGROUND
RNA interference (RNAi) in animals and post-transcriptional gene silencing (PTGS) in plants are related phenomena whose functions include the developmental regulation of gene expression and protection from transposable elements and viruses. Plant viruses respond by expressing suppressor proteins that interfere with the PTGS system.


RESULTS
Here we demonstrate that both transient and constitutive expression of the Tobacco etch virus HC-Pro silencing suppressor protein, which inhibits the maintenance of PTGS in plants, prevents dsRNA-induced RNAi of a lacZ gene in cultured Drosophila cells. Northern blot analysis of the RNA present in Drosophila cells showed that HC-Pro prevented degradation of lacZ RNA during RNAi but that there was accumulation of the short (23nt) RNA species associated with RNAi. A mutant HC-Pro that does not suppress PTGS in plants also does not affect RNAi in Drosophila. Similarly, the Cucumber mosaic virus 2b protein, which inhibits the systemic spread of PTGS in plants, does not suppress RNAi in Drosophila cells. In addition, we have used the Drosophila system to demonstrate that the 16K cysteine-rich protein of Tobacco rattle virus, which previously had no known function, is a silencing suppressor protein.


CONCLUSIONS
These results indicate that at least part of the process of RNAi in Drosophila and PTGS in plants is conserved, and that plant virus silencing suppressor proteins may be useful tools to investigate the mechanism of RNAi.
Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK. breavy@scri.sari.ac.uk
Brian
B
Reavy
Sheila
S
Dawson
Tomas
T
Canto
Stuart A
SA
MacFarlane
D000818:Animals; D002478:Cells, Cultured; D017799:Cucumovirus / Q000235:genetics; D004330:Drosophila / Q000737:chemistry / Q000166:cytology* / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal / Q000235:genetics*; D005814:Genes, Viral / Q000235:genetics / Q000502:physiology*; D010942:Plant Viruses / Q000235:genetics*; D034622:RNA Interference / Q000502:physiology*; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D014764:Viral Proteins / Q000235:genetics; D015678:Viral Structural Proteins / Q000235:genetics*; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D012331:RNA, Fungal; D034741:RNA, Small Interfering; D014764:Viral Proteins; D015678:Viral Structural Proteins; D001616:beta-Galactosidase