Spontaneous reactivation of a silent telomeric transgene in a human cell line

Joseph A. Baur, Jerry W. Shay, Woodring E. Wright

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Subtelomeric reporter genes in human cells are silenced in a telomere length-dependent manner. Here we show that a subtelomeric reporter gene is expressed in only a subpopulation of cells within a clone and that this heterogeneity is generated by switching between expression states. We observed frequent reversion from the silenced state back to active expression. This process was more prominent for subtelomeric transgenes; however, we also observed cases of spontaneous reversion in control clones bearing the reporter at an internal site. We additionally show that treatment of these cells with 5-bromodeoxyuridine results in strong activation of the transgene. Although similar findings have been reported previously in mouse cells, this is, to our knowledge, the first direct observation of ongoing fluctuations in transcription in clonal populations of human cells. Our results suggest that this mechanism, as opposed to progressive silencing or a delayed fixing of expression states, accounts for the variegation in expression observed for subtelomeric transgenes in human cells. These data imply that telomere shortening during human aging could lead to stochastic activation of subtelomeric genes.

Original languageEnglish (US)
Pages (from-to)240-246
Number of pages7
Issue number5
StatePublished - Feb 2004

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)


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