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Nature Genetics  17, 498 - 502 (1997)

Reconstitution of human telomerase with the template RNA component hTR and the catalytic protein subunit hTRT

Scott L. Weinrich1, Ron Pruzan1, Libin Ma1, Michel Ouellette2, Valeric M. Tesmer2, Shawn E. Holt2, Andrea G. Bodnar1, Serge Lichtsteiner1, Nam W. Kim1, James B. Trager1, Rebecca D. Taylor1, Ruben Carlos1, William H. Andrews1, 3, Woodring E. Wright2, Jerry W. Shay2, Calvin B. Harley1 & Gregg B. Morin1, 4

  lGeron Corporation, 230 Constitution Drive, Menlo Park, Calfornia 94025, USA.

  2The University of Texas Southwestern Medical Center, Department of Cell Biology and Neuroscience, 5323 Harry Hines Boulevard, Dallas, Texas 75235-9039, USA.

  3Current address: EOS Biotechnology, 750 Gateway Blvd., So. San Francisco, CA, 94080, USA.


The maintenance of chromosome termini, or telomeres, requires the action of the enzyme telomerase, as conventional DNA poly-merases cannot fully replicate the ends of linear molecules1−4. Telomerase is expressed and telomere length is maintained in human germ cells and the great majority of primary human tumours5,6. However, telomerase is not detectable in most normal somatic cells; this corresponds to the gradual telomere loss observed with each cell division7−9. It has been proposed that telomere erosion eventually signals entry into senescence or cell crisis and that activation of telomerase is usually required for immortal cell proliferation10. In addition to the human telomerase RNA component (hTR; ref. 11), TP1/TLP1 (refs 12,13), a protein that is homologous to the p80 protein associated with the Tetrahymena enzyme14, has been identified in humans. More recently, the human telomerase reverse transcriptase (hTRT; refs 15, 16), which is homologous to the reverse transcriptase (RT)-like proteins associated with the Euplotes aediculatus (Ea_p123), Saccharomyces cerevisiae (Est2p) and Schizosaccharomyces pombe (SpTrt!) telomerases15,17, has been reported to be a telomerase protein subunit. A catalytic function has been demonstrated for Est2p in the RT-like class but not for p80 or its homologues17,18. We now report that in vitro transcription and translation of hTRT when co-synthesized or mixed with hTR reconstitutes telomerase activity that exhibits enzymatic properties like those of the native enzyme. Single amino-acid changes in conserved telomerase-specific and RT motifs reduce or abolish activity, providing direct evidence that hTRT is the catalytic protein component of telomerase. Normal human diploid cells transiently expressing hTRT possessed telomerase activity, demonstrating that hTRT is the limiting component necessary for restoration of telomerase activity in these cells. The ability to reconstitute telomerase permits further analysis of its biochemical and biological roles in cell aging and carcinogenesis.

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Nature Genetics
ISSN: 1061-4036
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