Rapid methylation of genomic DNA in proliferating T-cells from bovine thymocytes

Hiroshi Sano, Hiroshi Noguchi, Ikuko Kodama, Tsunetoshi Itoh

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1 Citation (Scopus)


Two subpopulations of bovine calf thymus cells were separated by buoyant density centrifugation. The low-density cells (L-cells) showed high response to T-cell mitogens, while the high density cells (H-cells) did not. The DNA-metabolizing enzyme activities were elevated 10-fold in L-cells in comparison with those in H-cells. L-cells contained a DNA-replicating complex, DNA replitase, while H-cells did not. These observations suggested that L-cells were proliferating, mature T-cells and H-cells were dying intrathymic cells. A DNA methyltransferase was associated with DNA replitase in L-cells. In order to determine whether replitase-associated DNA methyltransferase functions at replicating regions, the methylation pattern of genomic DNA of L-cells was compared with that of H-cells. No significant difference was found in the extent of CpG dinucleotide methylation, and in the location of mC in the satellite I DNA sequence as identified by Southern hybridization and direct sequencing. Thus the majority of methylation patterns of genomic DNA did not change during T-cell development in the thymus. The results indicated that the methylation patterns were rapidly maintained in proliferating T-cells. Although methods employed in the present study might not be sensitive enough to detect transient hemimethylation, it is suggested that the rapid methylation might be catalyzed, albeit not completely, by a DNA methyltransferase associated with the DNA replitase complex.

Original languageEnglish
Pages (from-to)274-281
Number of pages8
JournalBBA - Gene Structure and Expression
Issue number3
Publication statusPublished - 1988 Sept 7
Externally publishedYes


  • (Bovine thymocyte)
  • DNA methylation
  • DNA replitase complex
  • T cell differentiation

ASJC Scopus subject areas

  • Structural Biology
  • Biophysics
  • Biochemistry
  • Genetics


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