DNA Methyltransferase Inhibition in Normal Human Fibroblasts Induces a p21-dependent Cell Cycle Withdrawal

Juan I. Young, James R. Smith

Research output: Contribution to journalArticlepeer-review

61 Scopus citations


Maintenance of methylation patterns in the mammalian genome by DNA (cytosine-5) methyltransferases (DNAMeTase) is required for normal cell and tissue function. Inhibition of DNAMeTase in cultured cells induces the expression of p21, a cyclin-dependent kinase (Cdk) inhibitor critical for cells to enter replicative senescence. We investigated the effects of DNAMeTase inhibition in normal human fibroblasts and found that it induces an irreversible growth arrest. Cells arrested by DNAMeTase inhibition became enlarged and had a flat morphology, exhibited an increased expression of collagenase and p21, and the DNA synthesis block could be overcome by the introduction of the SV40 large T antigen, all characteristics of senescent cells. In contrast, normal human fibroblasts lacking a functional p21 gene fail to undergo cell cycle arrest following DNAMeTase inhibition, indicating that p21 is an essential component of this arrest. Furthermore, DNAMeTase activity was reduced as cells approached the end of their proliferative potential. These data suggest that DNAMeTase could be an integral part of the mechanisms by which cells count the number of cell divisions completed and initiate a signaling cascade that ultimately results in the senescent phenotype.

Original languageEnglish (US)
Pages (from-to)19610-19616
Number of pages7
JournalJournal of Biological Chemistry
Issue number22
StatePublished - Jun 1 2001
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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