Endogenous Telomerase Reverse Transcriptase N-Terminal Tagging Affects Human Telomerase Function at Telomeres In Vivo

Mol Cell Biol. 2017 Jan 19;37(3):e00541-16. doi: 10.1128/MCB.00541-16. Print 2017 Feb 1.


Telomerase action at telomeres is essential for the immortal phenotype of stem cells and the aberrant proliferative potential of cancer cells. Insufficient telomere maintenance can cause stem cell and tissue failure syndromes, while increased telomerase levels are associated with tumorigenesis. Both pathologies can arise from only small perturbation of telomerase function. To analyze telomerase at its low endogenous expression level, we genetically engineered human pluripotent stem cells (hPSCs) to express various N-terminal fusion proteins of the telomerase reverse transcriptase from its endogenous locus. Using this approach, we found that these modifications can perturb telomerase function in hPSCs and cancer cells, resulting in telomere length defects. Biochemical analysis suggests that this defect is multileveled, including changes in expression and activity. These findings highlight the unknown complexity of telomerase structural requirements for expression and function in vivo.

Keywords: CRISPR/Cas9; embryonic stem cells; genome editing; pluripotent stem cells; telomerase; telomeres.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Southern
  • Epitopes / metabolism*
  • Gene Editing
  • Genotype
  • Human Embryonic Stem Cells / metabolism
  • Humans
  • Phenotype
  • Repetitive Sequences, Nucleic Acid / genetics
  • Telomerase / metabolism*
  • Telomere / metabolism*
  • Telomere Homeostasis


  • Epitopes
  • Telomerase