Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Telomerase activity is restored in human cells by ectopic expression of hTERT (hEST2), the catalytic subunit of telomerase


The expression of telomerase, the enzyme that synthesizes telomeric DNA de novo, is suppressed in normal somatic human cells but is reactivated during tumorigenesis. This reactivation appears to arrest the normal loss of telomeric DNA incurred as human cells divide. Since continual loss of telomeric DNA is predicted to eventually limit cell proliferation, activation of telomerase in cancer cells may represent an important step in the acquisition of the cell immortalization which occurs during tumor progression. The telomerase holoenzyme is composed of both RNA and protein subunits. In humans, mRNA expression of hTERT (hEST2), the candidate telomerase catalytic subunit gene, appears to parallel the levels of telomerase enzyme activity, suggesting that induction of hTERT is necessary and perhaps sufficient for expression of telomerase activity in tumor cells. To test this model directly, we ectopically expressed an epitope-tagged version of hTERT in telomerase-negative cells and show that telomerase activity was induced to levels comparable to those seen in immortal telomerase-positive cells and that the expressed hTERT protein was physically associated with the cellular telomerase activity. We conclude that synthesis of the hTERT telomerase subunit represents the rate-limiting determinant of telomerase activity in these cells and that this protein, once expressed, becomes part of the functional telomerase holoenzyme.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Prices vary by article type



Prices may be subject to local taxes which are calculated during checkout

Similar content being viewed by others

Author information

Authors and Affiliations


Rights and permissions

Reprints and Permissions

About this article

Cite this article

Counter, C., Meyerson, M., Eaton, E. et al. Telomerase activity is restored in human cells by ectopic expression of hTERT (hEST2), the catalytic subunit of telomerase. Oncogene 16, 1217–1222 (1998).

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


This article is cited by


Quick links