Minimal role of base excision repair in TET-induced global DNA demethylation in HEK293T cells

Chunlei Jin, Taichun Qin, Michelle Craig Barton, Jaroslav Jelinek, Jean Pierre J. Issa

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Oxidation of 5-methylcytosine by TET family proteins can induce DNA replication-dependent (passive) DNA demethylation and base excision repair (BER)-based (active) DNA demethylation. The balance of active vs. passive TET-induced demethylation remains incompletely determined. In the context of large scale DNA demethylation, active demethylation may require massive induction of the DNA repair machinery and thus compromise genome stability. To study this issue, we constructed a tetracycline-controlled TET-induced global DNA demethylation system in HEK293T cells. Upon TET overexpression, we observed induction of DNA damage and activation of a DNA damage response; however, BER genes are not upregulated to promote DNA repair. Depletion of TDG (thymine DNA glycosylase) or APEX1 (apurinic/apyrimidinic endonuclease 1), two key BER enzymes, enhances rather than impairs global DNA demethylation, which can be explained by stimulated proliferation. By contrast, growth arrest dramatically blocks TET-induced global DNA demethylation. Thus, in the context of TET-induction in HEK293T cells, the DNA replication-dependent passive mechanism functions as the predominant pathway for global DNA demethylation. In the same context, BER-based active demethylation is markedly restricted by limited BER upregulation, thus potentially preventing a disastrous DNA damage response to extensive active DNA demethylation.

Original languageEnglish (US)
Pages (from-to)1006-1013
Number of pages8
Issue number11
StatePublished - 2015
Externally publishedYes


  • Base excision repair
  • DNA damage
  • DNA demethylation pathway
  • DNA replication
  • TET genes

ASJC Scopus subject areas

  • Molecular Biology
  • Cancer Research


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