title: The p122 subunit of Tobacco Mosaic Virus replicase is a potent silencing suppressor and compromises both small interfering RNA- and microRNA-mediated pathways.
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.
authors: Agricultural Biotechnology Center, Plant Biology Institute, H-2101 Gödöllo, Hungary.
authors: Tibor
authors: T
authors: Csorba
authors: Aurelie
authors: A
authors: Bovi
authors: Tamás
authors: T
authors: Dalmay
authors: József
authors: J
authors: Burgyán
mesh_terms: D021581:Active Transport, Cell Nucleus; D016960:Agrobacterium tumefaciens / Q000378:metabolism; D000818:Animals; D017360:Arabidopsis / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D019175:DNA Methylation; D004330:Drosophila; D020868:Gene Silencing; D049452:Green Fluorescent Proteins / Q000378:metabolism; D035683:MicroRNAs / Q000378:metabolism*; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D012324:RNA-Dependent RNA Polymerase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D035683:MicroRNAs; D034741:RNA, Small Interfering; D049452:Green Fluorescent Proteins; C085103:tobacco mosaic virus replicase; D012324:RNA-Dependent RNA Polymerase
references: Genes Dev. 2006 Dec 1;20(23):3255-68
references: 17158744
references: J Virol. 2007 Apr;81(8):3797-806
references: 17267504
references: Nat Genet. 2005 Jul;37(7):761-5
references: 15924141
references: Mol Cell. 2005 Aug 5;19(3):421-8
references: 16061187
references: Proc Natl Acad Sci U S A. 2005 Aug 16;102(33):11928-33
references: 16081530
references: Curr Biol. 2005 Aug 23;15(16):1501-7
references: 16111943
references: Proc Natl Acad Sci U S A. 2005 Sep 6;102(36):12984-9
references: 16129836
references: Genes Dev. 2005 Sep 15;19(18):2164-75
references: 16131612
references: Plant Physiol. 2005 Aug;138(4):2145-54
references: 16040653
references: Curr Biol. 2007 May 1;17(9):818-23
references: 17442570
references: RNA. 2007 Aug;13(8):1268-78
references: 17592042
references: Methods. 2003 Aug;30(4):330-6
references: 12828947
references: Nature. 2003 Sep 18;425(6955):257-63
references: 12931144
references: J Virol. 2003 Oct;77(20):11016-26
references: 14512550
references: Cell. 2003 Oct 17;115(2):199-208
references: 14567917
references: Nature. 2003 Dec 18;426(6968):874-8
references: 14661029
references: Cell. 2003 Dec 26;115(7):799-811
references: 14697199
references: EMBO J. 2004 Feb 25;23(4):876-84
references: 14976549
references: Cell. 2004 Mar 19;116(6):831-41
references: 15035985
references: Cell. 2004 Apr 2;117(1):83-94
references: 15066284
references: Trends Plant Sci. 2004 Feb;9(2):76-83
references: 15102373
references: PLoS Biol. 2004 May;2(5):E104
references: 15024409
references: Plant Cell. 2004 May;16(5):1235-50
references: 15084715
references: Genes Dev. 2004 May 15;18(10):1179-86
references: 15131083
references: Plant Cell. 2004 Aug;16(8):2001-19
references: 15258262
references: Genome Biol. 2004;5(9):R65
references: 15345049
references: Genes Dev. 2004 Sep 15;18(18):2237-42
references: 15371337
references: Nature. 2004 Sep 16;431(7006):356-63
references: 15372043
references: Nature. 2004 Sep 16;431(7006):364-70
references: 15372044
references: Mol Cell. 2004 Oct 8;16(1):69-79
references: 15469823
references: Nucleic Acids Res. 1986 Nov 11;14(21):8291-305
references: 3786131
references: Virology. 1993 Jun;194(2):697-704
references: 8503183
references: FEBS Lett. 1994 Aug 15;350(1):5-8
references: 7545946
references: Nucleic Acids Res. 1998 Nov 1;26(21):4983-8
references: 9776763
references: J Virol. 1999 Apr;73(4):2633-40
references: 10074108
references: Plant Cell. 2000 Mar;12(3):369-79
references: 10715323
references: Virology. 2001 Apr 10;282(2):320-8
references: 11289814
references: Plant J. 2001 Sep;27(6):581-90
references: 11576441
references: Plant Cell. 2002 Feb;14(2):359-72
references: 11884680
references: J Virol. 2002 Jul;76(13):6815-24
references: 12050394
references: EMBO J. 2002 Jun 17;21(12):3070-80
references: 12065420
references: Science. 2003 Jan 31;299(5607):716-9
references: 12522258
references: Dev Cell. 2003 Feb;4(2):205-17
references: 12586064
references: J Gen Virol. 2003 Apr;84(Pt 4):975-80
references: 12655099
references: Curr Biol. 2003 Apr 29;13(9):784-9
references: 12725739
references: Curr Biol. 2003 May 13;13(10):843-8
references: 12747833
references: Science. 2005 Feb 11;307(5711):932-5
references: 15705854
references: Nat Rev Genet. 2005 Mar;6(3):206-20
references: 15703763
references: Genes Dev. 2005 Mar 1;19(5):517-29
references: 15741316
references: Proc Natl Acad Sci U S A. 2005 Mar 8;102(10):3691-6
references: 15738428
references: Cell. 2005 Mar 11;120(5):613-22
references: 15766525
references: Science. 2005 Apr 1;308(5718):118-20
references: 15692015
references: Cell. 2005 Apr 22;121(2):207-21
references: 15851028
references: J Virol. 2005 Jun;79(12):7812-8
references: 15919934
references: FEBS Lett. 2005 Oct 31;579(26):5923-31
references: 16144699
references: Cell. 2005 Nov 18;123(4):607-20
references: 16271386
references: Nat Struct Mol Biol. 2005 Nov;12(11):952-7
references: 16228003
references: Nucleic Acids Res. 2006;34(2):462-71
references: 16421273
references: Proc Natl Acad Sci U S A. 2006 Feb 7;103(6):1994-9
references: 16446454
references: Mol Cell. 2006 Apr 7;22(1):129-36
references: 16600876
references: Trends Genet. 2006 May;22(5):268-80
references: 16567016
references: FEBS Lett. 2006 May 29;580(13):3117-20
references: 16678167
references: J Virol. 2006 Jun;80(12):5747-56
references: 16731914
references: Nat Genet. 2006 Jun;38 Suppl:S31-6
references: 16736022
references: EMBO J. 2006 Jun 21;25(12):2768-80
references: 16724105
references: Nucleic Acids Res. 2006;34(21):6233-46
references: 17090584