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Structural insights into mechanisms of the small RNA methyltransferase HEN1
Author(s) -
Huang Ying,
Ji Lijuan,
Huang Qichen,
Vassylyev Dmitry,
Chen Xuemei,
Ma JinBiao
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.499.6
Subject(s) - trans acting sirna , rna , argonaute , rna induced transcriptional silencing , rna induced silencing complex , small rna , biology , rna silencing , small interfering rna , riboswitch , rasirna , non coding rna , methyltransferase , genetics , microbiology and biotechnology , rna interference , methylation , gene
RNA silencing is a conserved regulatory mechanism in fungi, plants and animals that regulates gene expression and defence against viruses and transgenes. Small silencing RNAs of approx 20–30 nucleotides and their associated effector proteins, the Argonaute family proteins, are the central components in RNA silencing. A subset of small RNAs, such as microRNAs and small interfering RNAs (siRNAs) in plants, Piwi‐interacting RNAs in animals and siRNAs in Drosophila, requires an additional crucial step for their maturation; that is, 2′‐O‐methylation on the 3′ terminal nucleotide. A conserved S‐adenosyl‐l‐methionine‐dependent RNA methyltransferase, HUA ENHANCER 1 (HEN1), and its homologues are responsible for this specific modification. Here we report the 3.1 Å crystal structure of full‐length HEN1 from Arabidopsis in complex with a 22‐nucleotide small RNA duplex and cofactor product S‐adenosyl‐l‐homocysteine. Highly cooperative recognition of the small RNA substrate by multiple RNA binding domains and the methyltransferase domain in HEN1 measures the length of the RNA duplex and determines the substrate specificity. Metal ion coordination by both 2′ and 3′ hydroxyls on the 3′‐terminal nucleotide and four invariant residues in the active site of the methyltransferase domain suggests a novel Mg2+‐dependent 2′‐O‐methylation mechanism.