Evidence that cytosine residues within 5'-CCTGG-3' pentanucleotides can be methylated in human DNA independently of the methylating system that modifies 5'-CG-3' dinucleotides

DNA Cell Biol. 2000 Sep;19(9):521-6. doi: 10.1089/104454900439755.

Abstract

In contrast to the complex sequence specificities of the prokaryotic DNA methylating systems, the mammalian machinery identified thus far methylates cytosine residues within the context of a 5'-CG-3' dinucleotide. To explore the possibility that cytosine residues that do not precede guanine may be independently methylated in mammalian DNA, we have examined a region of the human myogenic gene, Myf-3, which is not targeted by the methylating system that methylates 5'-CG-3' dinucleotides. Our investigations have revealed cytosine methylation within the 5'-CCTGG-3' pentanucleotides specified by the 0.8-kb Myf-3 probe. We have also found that in DNA from neoplastic cells, in which 5'-CG-3' dinucleotides within Myf-3 become abnormally hypermethylated, cytosine residues within 5'-CCTGG-3' pentanucleotides are not methylated. Moreover, methylation of 5'-CCTGG-3' pentanucleotides was not detected within the closely related Myf-4 gene, which is normally 5'-CG-3' hypermethylated. These findings indicate the existence of a system that methylates 5'-CCTGG-3' pentanucleotides independently of the system that methylates cytosine residues within 5'-CG-3' dinucleotides. It is possible that the 5'-CCTGG-3' methylating system influences the fate of foreign integrated DNA.

MeSH terms

  • Animals
  • Base Sequence
  • Blotting, Southern
  • Cytosine / metabolism*
  • DNA / chemistry
  • DNA / metabolism*
  • DNA Methylation*
  • DNA Probes
  • Humans
  • MyoD Protein / genetics
  • Oligonucleotides / chemistry*
  • Oligonucleotides / metabolism

Substances

  • DNA Probes
  • MyoD Protein
  • MyoD1 myogenic differentiation protein
  • Oligonucleotides
  • Cytosine
  • DNA