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National Institute of Environmental Health Sciences

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Your Environment. Your Health.

Publication Detail

Title: A histone methylation-dependent DNA methylation pathway is uniquely impaired by deficiency in Arabidopsis S-adenosylhomocysteine hydrolase.

Authors: Mull, Lori; Ebbs, Michelle L; Bender, Judith

Published In Genetics, (2006 Nov)

Abstract: S-adenosylhomocysteine hydrolase (SAH) is a key enzyme in the maintenance of methylation homeostasis in eukaryotes because it is needed to metabolize the by-product of transmethylation reactions, S-adenosylhomocysteine (AdoHcy), which causes by-product inhibition of methyltransferases (MTase's). Complete loss of SAH function is lethal. Partial loss of SAH function causes pleiotropic effects including developmental abnormalities and reduced cytosine methylation. Here we describe a novel partial-function missense allele of the Arabidopsis SAH1 gene that causes loss of cytosine methylation specifically in non-CG contexts controlled by the CMT3 DNA MTase and transcriptional reactivation of a silenced reporter gene, without conferring developmental abnormalities. The CMT3 pathway depends on histone H3 lysine 9 methylation (H3 mK9) to guide DNA methylation. Our results suggest that this pathway is uniquely sensitive to SAH impairment because of its requirement for two transmethylation reactions that can both be inhibited by AdoHcy. Our results further suggest that gene silencing pathways involving an interplay between histone and DNA methylation in other eukaryotes can be selectively impaired by controlled SAH downregulation.

PubMed ID: 16951055 Exiting the NIEHS site

MeSH Terms: Adenosylhomocysteinase/chemistry; Adenosylhomocysteinase/deficiency*; Adenosylhomocysteinase/genetics; Alleles; Amino Acid Sequence; Arabidopsis Proteins/antagonists & inhibitors; Arabidopsis Proteins/genetics; Arabidopsis/enzymology; Arabidopsis/genetics; DNA Methylation*; DNA, Plant/metabolism; Gene Silencing; Genes, Plant; Genes, Reporter; Genetic Complementation Test; Histone-Lysine N-Methyltransferase/antagonists & inhibitors; Histone-Lysine N-Methyltransferase/genetics; Histones/metabolism; Molecular Sequence Data; Mutation, Missense; Protein Structure, Secondary; Protein Structure, Tertiary; S-Adenosylhomocysteine/metabolism; Sequence Homology, Amino Acid; Site-Specific DNA Methyltransferase (Cytosine-Specific)/antagonists & inhibitors; Site-Specific DNA Methyltransferase (Cytosine-Specific)/genetics; Trans-Activation (Genetics)

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