Small RNA binding is a common strategy to suppress RNA silencing by several viral suppressors

• Published in: The EMBO journal Vol. 25; no. 12; pp. 2768 - 2780
• Main Authors: Lakatos, L, Csorba, T, Pantaleo, V, Chapman, E.J, Carrington, J.C, Liu, Y.P, Dolja, V.V, Fernández Calvino, L, López-Moya, J.J, Burgyán, J
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 21.06.2006; Blackwell Publishing Ltd
• Subjects: Animals; Arabidopsis - virology; Base Pairing; Beet yellows virus; binding capacity; Binding sites; defense mechanisms; disease resistance; Drosophila - metabolism; Embryo, Nonmammalian - metabolism; gene silencing; Immunology; infection; Insects; microRNA; MicroRNAs - metabolism; Nicotiana - virology; Nicotiana benthamiana; Plant Leaves - virology; Plant Viruses - physiology; resistance mechanisms; Ribonucleic acid; RNA; RNA Interference; RNA silencing; RNA Stability; RNA, Small Interfering - metabolism; RNA-binding proteins; RNA-Induced Silencing Complex - metabolism; silencing suppressors; siRNA; small interfering RNA; small RNA binding; Tobacco etch virus; viral proteins; Viral Proteins - metabolism; viral suppressors; virud-induced RNA silencing; Viruses
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/sj.emboj.7601164

RNA silencing is an evolutionarily conserved system that functions as an antiviral mechanism in higher plants and insects. To counteract RNA silencing, viruses express silencing suppressors that interfere with both siRNA‐ and microRNA‐guided silencing pathways. We used comparative in vitro and in vivo approaches to analyse the molecular mechanism of suppression by three well‐studied silencing suppressors. We found that silencing suppressors p19, p21 and HC‐Pro each inhibit the intermediate step of RNA silencing via binding to siRNAs, although the molecular features required for duplex siRNA binding differ among the three proteins. None of the suppressors affected the activity of preassembled RISC complexes. In contrast, each suppressor uniformly inhibited the siRNA‐initiated RISC assembly pathway by preventing RNA silencing initiator complex formation.