title: The catalytic subunit of Arabidopsis DNA polymerase α ensures stable maintenance of histone modification.
abstract: Mitotic inheritance of identical cellular memory is crucial for development in multicellular organisms. The cell type-specific epigenetic state should be correctly duplicated upon DNA replication to maintain cellular memory during tissue and organ development. Although a role of DNA replication machinery in maintenance of epigenetic memory has been proposed, technical limitations have prevented characterization of the process in detail. Here, we show that INCURVATA2 (ICU2), the catalytic subunit of DNA polymerase α in Arabidopsis, ensures the stable maintenance of repressive histone modifications. The missense mutant allele icu2-1 caused a defect in the mitotic maintenance of vernalization memory. Although neither the recruitment of CURLY LEAF (CLF), a SET-domain component of Polycomb Repressive Complex 2 (PRC2), nor the resultant deposition of the histone mark H3K27me3 required for vernalization-induced FLOWERING LOCUS C (FLC) repression were affected, icu2-1 mutants exhibited unstable maintenance of the H3K27me3 level at the FLC region, which resulted in mosaic FLC de-repression after vernalization. ICU2 maintains the repressive chromatin state at additional PRC2 targets as well as at heterochromatic retroelements. In icu2-1 mutants, the subsequent binding of LIKE-HETEROCHROMATIN PROTEIN 1 (LHP1), a functional homolog of PRC1, at PRC2 targets was also reduced. We demonstrated that ICU2 facilitates histone assembly in dividing cells, suggesting a possible mechanism for ICU2-mediated epigenetic maintenance.
authors.affiliation: Department of Biological Sciences, Seoul National University, Seoul, 151-742, Korea.
authors.forename: Youbong
authors.initials: Y
authors.lastname: Hyun
authors.forename: Hyein
authors.initials: H
authors.lastname: Yun
authors.forename: Kyunghyuk
authors.initials: K
authors.lastname: Park
authors.forename: Hyonhwa
authors.initials: H
authors.lastname: Ohr
authors.forename: Okchan
authors.initials: O
authors.lastname: Lee
authors.forename: Dong-Hwan
authors.initials: DH
authors.lastname: Kim
authors.forename: Sibum
authors.initials: S
authors.lastname: Sung
authors.forename: Yeonhee
authors.initials: Y
authors.lastname: Choi
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D020134:Catalytic Domain / Q000235:genetics / Q000502:physiology*; D004256:DNA Polymerase I / Q000235:genetics / Q000502:physiology*; D004795:Enzyme Stability / Q000235:genetics; D044127:Epigenesis, Genetic / Q000235:genetics; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D008938:Mitosis / Q000235:genetics; D020125:Mutation, Missense; D030821:Plants, Genetically Modified; D021122:Protein Subunits / Q000235:genetics / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D006657:Histones; D021122:Protein Subunits; C525567:INCURVATA2 protein, Arabidopsis; D004256:DNA Polymerase I