siRNAs compete with miRNAs for methylation by HEN1 in Arabidopsis.
Plant microRNAs (miRNAs) and small interfering RNAs (siRNAs) bear a 2'-O-methyl group on the 3'-terminal nucleotide. This methyl group is post-synthetically added by the methyltransferase protein HEN1 and protects small RNAs from enzymatic activities that target the 3'-OH. A mutagenesis screen for suppressors of the partial loss-of-function hen1-2 allele in Arabidopsis identified second-site mutations that restore miRNA methylation. These mutations affect two subunits of the DNA-dependent RNA polymerase IV (Pol IV), which is essential for the biogenesis of 24 nt endogenous siRNAs. A mutation in RNA-dependent RNA polymerase 2, another essential gene for the biogenesis of endogenous 24-nt siRNAs, also rescued the defects in miRNA methylation of hen1-2, revealing a previously unsuspected, negative influence of siRNAs on HEN1-mediated miRNA methylation. In addition, our findings imply the existence of a negative modifier of HEN1 activity in the Columbia genetic background.
Yu
Bin
B
Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA.
Bi
Liu
L
Zhai
Jixian
J
Agarwal
Manu
M
Li
Shengben
S
Wu
Qingfa
Q
Ding
Shou-Wei
SW
Meyers
Blake C
BC
Vaucheret
Hervé
H
Chen
Xuemei
X
D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D005298:Fertility; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D035683:MicroRNAs / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D034741:RNA, Small Interfering / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics; D013489:Suppression, Genetic
D029681:Arabidopsis Proteins; C450825:HEN1 protein, Arabidopsis; D035683:MicroRNAs; D034741:RNA, Small Interfering; D008780:Methyltransferases; C499181:RNA polymerase IV, Arabidopsis; C538841:RNA polymerase V, Arabidopsis; C519655:RDR2 protein, Arabidopsis; D012324:RNA-Dependent RNA Polymerase; D012321:DNA-Directed RNA Polymerases
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