title: Requirement of CHROMOMETHYLASE3 for maintenance of CpXpG methylation.
abstract: Epigenetic silenced alleles of the Arabidopsis SUPERMAN locus (the clark kent alleles) are associated with dense hypermethylation at noncanonical cytosines (CpXpG and asymmetric sites, where X = A, T, C, or G). A genetic screen for suppressors of a hypermethylated clark kent mutant identified nine loss-of-function alleles of CHROMOMETHYLASE3 (CMT3), a novel cytosine methyltransferase homolog. These cmt3 mutants display a wild-type morphology but exhibit decreased CpXpG methylation of the SUP gene and of other sequences throughout the genome. They also show reactivated expression of endogenous retrotransposon sequences. These results show that a non-CpG DNA methyltransferase is responsible for maintaining epigenetic gene silencing.
authors.affiliation: Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Lindroth
authors.forename: X
authors.initials: X
authors.lastname: Cao
authors.forename: J P
authors.initials: JP
authors.lastname: Jackson
authors.forename: D
authors.initials: D
authors.lastname: Zilberman
authors.forename: C M
authors.initials: CM
authors.lastname: McCallum
authors.forename: S
authors.initials: S
authors.lastname: Henikoff
authors.forename: S E
authors.initials: SE
authors.lastname: Jacobsen
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D018899:CpG Islands; D003433:Crosses, Genetic; D003596:Cytosine / Q000378:metabolism; D019175:DNA Methylation; D015257:DNA-Cytosine Methylases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015226:Dinucleoside Phosphates / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009841:Oligonucleotides / Q000378:metabolism*; D010641:Phenotype; D017434:Protein Structure, Tertiary; D018626:Retroelements; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D029681:Arabidopsis Proteins; D003596:Cytosine; D015257:DNA-Cytosine Methylases; D015226:Dinucleoside Phosphates; D009841:Oligonucleotides; D018626:Retroelements; D014157:Transcription Factors; C096661:superman protein, Arabidopsis; C015772:CpG dinucleotide; C429766:CMT3 protein, Arabidopsis