title: Preventing transcriptional gene silencing by active DNA demethylation.
abstract: DNA methylation is important for stable transcriptional gene silencing. DNA methyltransferases for de novo as well as maintenance methylation have been well characterized. However, enzymes responsible for active DNA demethylation have been elusive and several reported mechanisms of active demethylation have been controversial. There has been a critical need for genetic analysis in order to firmly establish an in vivo role for putative DNA demethylases. Mutations in the bifunctional DNA glycosylase/lyase ROS1 in Arabidopsis cause DNA hypermethylation and transcriptional silencing of specific genes. Recombinant ROS1 protein has DNA glycosylase/lyase activity on methylated but not unmethylated DNA substrates. Therefore, there is now strong genetic evidence supporting a base excision repair mechanism for active DNA demethylation. DNA demethylases may be critical factors for genome wide hypomethylation seen in cancers and possibly important for epigenetic reprogramming during somatic cell cloning and stem cell function.
authors.affiliation: Institute for Integrative Genome Biology, Department of Botany and Plant Sciences, University of California, Riverside, Riverside, CA 92521, USA.
authors.forename: Avnish
authors.initials: A
authors.lastname: Kapoor
authors.forename: Fernanda
authors.initials: F
authors.lastname: Agius
authors.forename: Jian-Kang
authors.initials: JK
authors.lastname: Zhu
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000378:metabolism / Q000502:physiology*; D002843:Chromatin / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D045647:DNA Glycosylases / Q000737:chemistry / Q000378:metabolism; D019175:DNA Methylation; D004260:DNA Repair; D020868:Gene Silencing; D016678:Genome; D018745:Genome, Plant; D006570:Heterochromatin / Q000737:chemistry; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins; D002843:Chromatin; D006570:Heterochromatin; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; C471271:ROS1 protein, Arabidopsis; D011994:Recombinant Proteins; D004247:DNA; D045647:DNA Glycosylases