RNAi targets a DNA virus

Rij PNA article 2012

In a recent paper in Proc Natl Acad Sci USA, Walter Bronkhorst, Koen van Cleef, Ronald van Rij (Dept. Medical Microbiology) and collaborators demonstrate that a DNA virus is targeted by an RNA-based immune response. The RNA interference (RNAi) pathway is a critical mechanism for defense against RNA viruses in plants, fungi and insects. In this response, viral double-stranded (ds) RNA replication intermediates are processed into small interfering RNAs that restrict virus replication. Using Drosophila melanogaster as a model, Bronkhorst et al now show that a double-stranded DNA virus is also targeted by the RNAi response. Using next generation sequencing, they provide evidence that viral dsRNA is processed by the nuclease Dicer-2 into small RNAs. Consequently, flies lacking essential components of the RNAi response are more sensitive to virus infection. The authors propose that transcription of both strands of the viral genome generates overlapping complementary RNA strands. These transcripts base-pair to form double-stranded RNA that initiates an antiviral RNAi response. These results provide important insight in the antiviral immune response of insects, which is important for our understanding of virus transmission by blood-feeding insects. Moreover, the results exemplify the sophisticated mechanism by which invertebrate animals, which lack the innate and adaptive immune system of mammals, protect themselves from virus infection. A. Walter Bronkhorst, Koen W. van Cleef, Nicolas Vodovar, Hervé Blanc, I. Agah Ince, Just Vlak, Maria-Carla Saleh, Ronald P. van Rij. 2012. The DNA virus Invertebrate Iridovirus 6 is a target of the Drosophila RNAi machinery. Proc Natl Acad Sci U S A, Epub ahead of print Nov 2012.

http://www.pnas.org/content/early/2012/11/14/1207213109.long


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