title: An ARGONAUTE4-containing nuclear processing center colocalized with Cajal bodies in Arabidopsis thaliana.
abstract: ARGONAUTE4 (AGO4) and RNA polymerase IV (Pol IV) are required for DNA methylation guided by 24 nucleotide small interfering RNAs (siRNAs) in Arabidopsis thaliana. Here we show that AGO4 localizes to nucleolus-associated bodies along with the Pol IV subunit NRPD1b; the small nuclear RNA (snRNA) binding protein SmD3; and two markers of Cajal bodies, trimethylguanosine-capped snRNAs and the U2 snRNA binding protein U2B''. AGO4 interacts with the C-terminal domain of NRPD1b, and AGO4 protein stability depends on upstream factors that synthesize siRNAs. AGO4 is also found, along with the DNA methyltransferase DRM2, throughout the nucleus at presumed DNA methylation target sites. Cajal bodies are conserved sites for the maturation of ribonucleoprotein complexes. Our results suggest a function for Cajal bodies as a center for the assembly of an AGO4/NRPD1b/siRNA complex, facilitating its function in RNA-directed gene silencing at target loci.
authors.affiliation: Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Carey Fei
authors.initials: CF
authors.lastname: Li
authors.forename: Olga
authors.initials: O
authors.lastname: Pontes
authors.forename: Mahmoud
authors.initials: M
authors.lastname: El-Shami
authors.forename: Ian R
authors.initials: IR
authors.lastname: Henderson
authors.forename: Yana V
authors.initials: YV
authors.lastname: Bernatavichute
authors.forename: Simon W-L
authors.initials: SW
authors.lastname: Chan
authors.forename: Thierry
authors.initials: T
authors.lastname: Lagrange
authors.forename: Craig S
authors.initials: CS
authors.lastname: Pikaard
authors.forename: Steven E
authors.initials: SE
authors.lastname: Jacobsen
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D060565:Argonaute Proteins; D001324:Autoantigens / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D002466:Cell Nucleolus / Q000235:genetics* / Q000378:metabolism; D020541:Coiled Bodies / Q000235:genetics* / Q000378:metabolism; D019175:DNA Methylation; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D020868:Gene Silencing / Q000502:physiology*; D046911:Macromolecular Substances / Q000378:metabolism; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics* / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000235:genetics / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000235:genetics / Q000378:metabolism; D055517:snRNP Core Proteins
chemical_list: C471209:AGO4 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D001324:Autoantigens; D029721:Drosophila Proteins; D046911:Macromolecular Substances; D021122:Protein Subunits; D034741:RNA, Small Interfering; D012342:RNA, Small Nuclear; D017411:Ribonucleoproteins, Small Nuclear; C490401:SmD3 protein, Drosophila; D055517:snRNP Core Proteins; D008780:Methyltransferases; C470732:DRM2 protein, Arabidopsis; C499181:RNA polymerase IV, Arabidopsis; D012321:DNA-Directed RNA Polymerases