Dynamic regulation of ARGONAUTE4 within multiple nuclear bodies in Arabidopsis thaliana.
DNA methylation directed by 24-nucleotide small RNAs involves the small RNA-binding protein ARGONAUTE4 (AGO4), and it was previously shown that AGO4 localizes to nucleolus-adjacent Cajal bodies, sites of snRNP complex maturation. Here we demonstrate that AGO4 also localizes to a second class of nuclear bodies, called AB-bodies, which are found immediately adjacent to condensed 45S ribosomal DNA (rDNA) sequences. AB-bodies also contain other proteins involved in RNA-directed DNA methylation including NRPD1b (a subunit of the RNA Polymerase IV complex, RNA PolIV), NRPD2 (a second subunit of this complex), and the DNA methyltransferase DRM2. These two classes of AGO4 bodies are structurally independent--disruption of one class does not affect the other--suggesting a dynamic regulation of AGO4 within two distinct nuclear compartments in Arabidopsis. Abolishing Cajal body formation in a coilin mutant reduced overall AGO4 protein levels, and coilin dicer-like3 double mutants showed a small decrease in DNA methylation beyond that seen in dicer-like3 single mutants, suggesting that Cajal bodies are required for a fully functioning DNA methylation system in Arabidopsis.
Li
Carey F
CF
Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America.
Henderson
Ian R
IR
Song
Liang
L
Fedoroff
Nina
N
Lagrange
Thierry
T
Jacobsen
Steven E
SE
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060565:Argonaute Proteins; D001483:Base Sequence; D002451:Cell Compartmentation; D020541:Coiled Bodies / Q000378:metabolism; D019175:DNA Methylation; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism; D004275:DNA, Ribosomal / Q000235:genetics / Q000378:metabolism; D017343:Genes, Plant; D042581:Intranuclear Space / Q000378:metabolism; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D030821:Plants, Genetically Modified; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism
C471209:AGO4 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D018744:DNA, Plant; D004275:DNA, Ribosomal; D034741:RNA, Small Interfering; D008780:Methyltransferases; C470732:DRM2 protein, Arabidopsis; C519654:DCL3 protein, Arabidopsis; D043244:Ribonuclease III