title: Viral suppression of RNA silencing by destabilisation of ARGONAUTE 1.
abstract: RNA silencing is a manifestation of a ubiquitous phenomenon that acts, at least in plants and some insects, as a natural defense mechanism against viruses. As a counter-strategy, viruses have evolved to encode silencing suppressor proteins (SSPs) that can block the defense response and evade the host immunity. Although numerous SSP have been identified, little information is available on the molecular basis of their mode of action. Among SSPs, the polerovirus protein P0 functions as an F-box protein that targets an essential actor of the silencing pathway. Our work demonstrates that one of the main targets is ARGONAUTE 1 (AGO1), a key component of the RISC effector complex. By a physical interaction with AGO1, P0 mediates AGO1 protein degradation in planta. This is the first report of a plant virus that exploits components of the host ubiquitination machinery to overcome RNA silencing. This unusual mode of action may provide some clues concerning the mechanism governing phloem tropism of poleroviruses.
authors.affiliation: Institut de Biologie Moléculaire des Plantes du CNRS; Strasbourg, France.
authors.forename: Diane
authors.initials: D
authors.lastname: Bortolamiol
authors.forename: Maghsoud
authors.initials: M
authors.lastname: Pazhouhandeh
authors.forename: Véronique
authors.initials: V
authors.lastname: Ziegler-Graff
references.citation: J Virol. 2002 Jul;76(13):6815-24
references.pmid: 12050394
references.citation: Curr Biol. 2007 Sep 18;17(18):1615-21
references.pmid: 17869109
references.citation: FEBS Lett. 2005 Oct 31;579(26):5858-71
references.pmid: 16242131
references.citation: Adv Virus Res. 1996;46:413-60
references.pmid: 8824705
references.citation: Nature. 2004 Sep 16;431(7006):356-63
references.pmid: 15372043
references.citation: EMBO J. 2003 Sep 1;22(17):4523-33
references.pmid: 12941703
references.citation: Curr Biol. 2007 Sep 18;17(18):1609-14
references.pmid: 17869110
references.citation: Nature. 2003 Dec 18;426(6968):874-8
references.pmid: 14661029
references.citation: Genes Dev. 2004 May 15;18(10):1187-97
references.pmid: 15131082
references.citation: Nat Genet. 2005 Dec;37(12):1356-60
references.pmid: 16273107
references.citation: EMBO J. 2006 Jun 21;25(12):2768-80
references.pmid: 16724105
references.citation: Cell. 2003 Dec 26;115(7):799-811
references.pmid: 14697199
references.citation: Proc Natl Acad Sci U S A. 2006 Feb 7;103(6):1994-9
references.pmid: 16446454
references.citation: Genes Dev. 2006 Dec 1;20(23):3255-68
references.pmid: 17158744
references.citation: Cell. 2007 Aug 10;130(3):413-26
references.pmid: 17693253
references.citation: Annu Rev Microbiol. 2006;60:503-31
references.pmid: 16768647