title: De novo CpG methylation on an artificial chromosome-like vector maintained for a long-term in mammalian cells.
abstract: OBJECTIVE
  To examine whether an autonomously replicating, artificial chromosome-like vector containing a long genomic DNA sequence (namely, Epigenosome-Nanog) undergoes de novo CpG methylation after maintenance in cultured cells for more than a half year.
  
  
  RESULTS
  Epigenosome-Nanog efficiently replicated in iPS cells after transfection. In HeLa and C2C12 cells Epigenosome-Nanog was stably maintained for more than eight months. The CpG methylation occurred de novo at the Nanog gene promoter region on the epigenosome in C2C12 cells but the degrees of methylation were much lower than those at the same CpG sites on the chromosomes. Among the four CpG sites at the region, the upstream two CpGs underwent methylation in a correlated manner while methylation at the downstream two CpGs was also correlated to each other, and these correlations were commonly shared between the epigenosome and the chromosome. CpG methylation thus was not solely dependent on the nucleotide sequence at the DNA locus.
  
  
  CONCLUSIONS
  The epigenosome may become a useful tool to study the mechanisms of epigenetic regulation of a genetic region of interest in mammalian cells.
authors.affiliation: Department of Immunology, Kyoto Prefectural University of Medicine, Kamikyo, Kyoto, 602-8566, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Nishioka
authors.affiliation: Department of Immunology, Kyoto Prefectural University of Medicine, Kamikyo, Kyoto, 602-8566, Japan.
authors.forename: Tsunao
authors.initials: T
authors.lastname: Kishida
authors.affiliation: Department of Life Science Frontiers, Center for iPS Cell Research and Application, Kyoto University, Kyoto, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Masui
authors.affiliation: Department of Immunology, Kyoto Prefectural University of Medicine, Kamikyo, Kyoto, 602-8566, Japan. mazda@koto.kpu-m.ac.jp.
authors.forename: Osam
authors.initials: O
authors.lastname: Mazda
mesh_terms: D000818:Animals; D018929:Cell Culture Techniques; D002460:Cell Line; D022201:Chromosomes, Artificial / Q000235:genetics*; D018899:CpG Islands; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D011401:Promoter Regions, Genetic
keywords: Artificial chromosome; CpG methylation; Epstein-Barr virus nuclear antigen 1 (EBNA1)