title: Arabidopsis CMT3 activity is positively regulated by AtSIZ1-mediated sumoylation.
abstract: The activities of mammalian DNA and histone methyltransferases are regulated by post-translational modifications such as phosphorylation and sumoylation; however, it is unclear how the activities of these enzymes are regulated at the post-translational level in plants. Here, we demonstrate that the DNA methylation activity of Arabidopsis CHROMOMETHYLASE 3 (CMT3) is positively regulated by the E3 SUMO ligase AtSIZ1. The methylation level of the Arabidopsis genome, including transposons, was significantly lower in the siz1-2 mutant than in wild-type plants. CMT3 was sumoylated by the E3 ligase activity of AtSIZ1 through a direct interaction, and the DNA methyltransferase activity of CMT3 was enhanced by this modification. In addition, the methylation levels of a large number of genes, including the nitrate reductase gene NIA2, were lower in siz1-2 and cmt3 plants than in wild-type plants. Furthermore, the CHG methylation activity of CMT3 was specific for NIA2and not NIA1 (the other nitrate reductase gene in Arabidopsis), indicating that CMT3 selectively regulates the CHG methylation levels of target genes. Taken together, our results indicate that the sumoylation of CMT3 is critical for its role in the control of gene expression and that AtSIZ1 positively controls the epigenetic repression of CMT3-mediated gene expression.
authors.affiliation: Department of Plant Science and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea.
authors.forename: Do Youn
authors.initials: DY
authors.lastname: Kim
authors.affiliation: Department of Plant Science and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea.
authors.forename: Yun Jung
authors.initials: YJ
authors.lastname: Han
authors.affiliation: Department of Plant Science and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea.
authors.forename: Sung-Il
authors.initials: SI
authors.lastname: Kim
authors.affiliation: School of Applied Biosciences, Kyungpook National University, Daegu 702-701, Republic of Korea.
authors.forename: Jong Tae
authors.initials: JT
authors.lastname: Song
authors.affiliation: Department of Plant Science and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea; Bio-MAX Institute, Seoul National University, Seoul 151-818, Republic of Korea. Electronic address: seohs@snu.ac.kr.
authors.forename: Hak Soo
authors.initials: HS
authors.lastname: Seo
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D019175:DNA Methylation; D015257:DNA-Cytosine Methylases / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008025:Ligases / Q000235:genetics* / Q000378:metabolism; D058207:Sumoylation
chemical_list: D029681:Arabidopsis Proteins; D015257:DNA-Cytosine Methylases; C429766:CMT3 protein, Arabidopsis; D008025:Ligases; C502552:SIZ1 protein, Arabidopsis
keywords: AtSIZ1; CMT3; DNA methylation; DNA methyltransferase; SUMO; Sumoylation