Human telomerase reverse transcriptase immortalizes bovine lens epithelial cells and suppresses differentiation through regulation of the ERK signaling pathway

J Biol Chem. 2005 Jun 17;280(24):22776-87. doi: 10.1074/jbc.M500032200. Epub 2005 Apr 22.


Telomerase is a specialized reverse transcriptase that extends telomeres of eukaryotic chromosomes. The functional telomerase complex contains a telomerase reverse transcriptase catalytic subunit and a telomerase template RNA. We have previously demonstrated that human telomerase reverse transcriptase (hTERT) catalytic subunit is functionally compatible with a telomerase template RNA from rabbit. In this study, we show that hTERT is also functionally compatible with a telomerase template RNA from bovine. Introduction of hTERT into bovine lens epithelial cells (BLECs) provides the transfected cells telomerase activity. The expressed hTERT in BLECs supports normal growth of the transfected cells for 108 population doublings so far, and these cells are still extremely healthy in both morphology and growth. In contrast, the vector-transfected cells display growth crisis after 20 population doublings. These cells run into cellular senescence due to shortening of the telomeres and also commit differentiation as indicated by the accumulation of the differentiation markers, beta-crystallin and filensin. hTERT prevents the occurrence of both events. By synthesizing new telomere, hTERT prevents replicative senescence, and through regulation of MEK/ERK, protein kinase C, and protein kinase A and eventual suppression of the MEK/ERK signaling pathway, hTERT inhibits differentiation of BLECs. Our finding that hTERT can suppress RAS/RAF/MEK/ERK signaling pathway to prevent differentiation provides a novel mechanism to explain how hTERT regulates cell differentiation.

Publication types

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

MeSH terms

  • Animals
  • Apoptosis
  • Blotting, Southern
  • Blotting, Western
  • Cattle
  • Cell Differentiation
  • Cell Line
  • Cell Proliferation
  • Cellular Senescence
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • DNA-Binding Proteins
  • Epithelial Cells / metabolism*
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • Humans
  • Immunoprecipitation
  • Lens, Crystalline / metabolism*
  • MAP Kinase Kinase 1 / metabolism
  • MAP Kinase Kinase 2 / metabolism
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Mutation
  • Protein Kinase C / metabolism
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction
  • Telomerase / chemistry*
  • Telomerase / metabolism
  • Telomere / ultrastructure
  • Time Factors
  • Transcription, Genetic
  • Transfection
  • beta-Galactosidase / metabolism


  • DNA-Binding Proteins
  • MAP2K2 protein, human
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C
  • Extracellular Signal-Regulated MAP Kinases
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • MAP Kinase Kinase 1
  • MAP Kinase Kinase 2
  • Telomerase
  • beta-Galactosidase