Atypical RNA polymerase subunits required for RNA-directed DNA methylation.
RNA-directed DNA methylation, one of several RNA interference-mediated pathways in the nucleus, has been documented in plants and in human cells. Despite progress in identifying the DNA methyltransferases, histone-modifying enzymes and RNA interference proteins needed for RNA-directed DNA methylation, the mechanism remains incompletely understood. We screened for mutants defective in RNA-directed DNA methylation and silencing of a transgene promoter in Arabidopsis thaliana and identified three drd complementation groups. DRD1 is a SNF2-like protein required for RNA-directed de novo methylation. We report here that DRD2 and DRD3 correspond to the second-largest subunit and largest subunit, respectively, of a fourth class of DNA-dependent RNA polymerase (polymerase IV) that is unique to plants. DRD3 is a functionally diversified homolog of NRPD1a or SDE4, identified in a separate screen for mutants defective in post-transcriptional gene silencing. The identical DNA methylation patterns observed in all three drd mutants suggest that DRD proteins cooperate to create a substrate for RNA-directed de novo methylation.
Kanno
Tatsuo
T
Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, UZA2, Pharmazie Zentrum, Althanstrasse 14/2D-541, A-1090 Vienna, Austria.
Huettel
Bruno
B
Mette
M Florian
MF
Aufsatz
Werner
W
Jaligot
Estelle
E
Daxinger
Lucia
L
Kreil
David P
DP
Matzke
Marjori
M
Matzke
Antonius J M
AJ
D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D019175:DNA Methylation; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing; D008969:Molecular Sequence Data; D009154:Mutation; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism*
D021122:Protein Subunits; D018749:RNA, Plant; C499181:RNA polymerase IV, Arabidopsis; D012321:DNA-Directed RNA Polymerases