The p122 Subunit of Tobacco Mosaic Virus Replicase Is a Potent Silencing Suppressor and Compromises both Small Interfering RNA- and MicroRNA-Mediated Pathways
- 1 November 2007
- journal article
- Published by American Society for Microbiology in Journal of Virology
- Vol. 81 (21), 11768-11780
- https://doi.org/10.1128/jvi.01230-07
Abstract
One of the functions of RNA silencing in plants is to defend against molecular parasites, such as viruses, retrotransposons, and transgenes. Plant viruses are inducers, as well as targets, of RNA silencing-based antiviral defense. Replication intermediates or folded viral RNAs activate RNA silencing, generating small interfering RNAs (siRNAs), which are the key players in the antiviral response. Viruses are able to counteract RNA silencing by expressing silencing-suppressor proteins. It has been shown that many of the identified silencing-suppressor proteins bind long double-stranded RNA or siRNAs and thereby prevent assembly of the silencing effector complexes. In this study, we show that the 122-kDa replicase subunit (p122) of crucifer-infecting Tobacco mosaic virus (cr-TMV) is a potent silencing-suppressor protein. We found that the p122 protein preferentially binds to double-stranded 21-nucleotide (nt) siRNA and microRNA (miRNA) intermediates with 2-nt 3′ overhangs inhibiting the incorporation of siRNA and miRNA into silencing-related complexes (e.g., RNA-induced silencing complex [RISC]) both in vitro and in planta but cannot interfere with previously programmed RISCs. In addition, our results also suggest that the virus infection and/or sequestration of the siRNA and miRNA molecules by p122 enhances miRNA accumulation despite preventing its methylation. However, the p122 silencing suppressor does not prevent the methylation of certain miRNAs in hst-15 mutants, in which the nuclear export of miRNAs is compromised.Keywords
This publication has 66 references indexed in Scilit:
- Identification of Nuclear Dicing Bodies Containing Proteins for MicroRNA Biogenesis in Living Arabidopsis PlantsCurrent Biology, 2007
- Cucumber mosaic virus-encoded 2b suppressor inhibits Arabidopsis Argonaute1 cleavage activity to counter plant defenseGenes & Development, 2006
- Four plant Dicers mediate viral small RNA biogenesis and DNA virus induced silencingNucleic Acids Research, 2006
- Small RNA binding is a common strategy to suppress RNA silencing by several viral suppressorsThe EMBO Journal, 2006
- AGO1 Homeostasis Entails Coexpression of MIR168 and AGO1 and Preferential Stabilization of miR168 by AGO1Molecular Cell, 2006
- Expression of Arabidopsis MIRNA GenesPlant Physiology, 2005
- Induction and suppression of RNA silencing: insights from viral infectionsNature Reviews Genetics, 2005
- The role of RNA interference in heterochromatic silencingNature, 2004
- RNA silencing in plantsNature, 2004
- A viral protein suppresses RNA silencing and binds silencing-generated, 21- to 25-nucleotide double-stranded RNAsThe EMBO Journal, 2002