Human Telomerase Isolated. |
Created September 1st, 1997. Copyright 1997 by Duane Hewitt
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The active component of the human telomerase complex has
now been cloned. This has been accomplished by two
groups working independently (1,2) They used the sequences
obtained from the cloning of
this gene in Euplotes. This
protein has an important if not essential role in both
cancer and aging.
When the equivalent gene is deleted in yeast the cells age
rapidly due to telomere loss. This phenomenon is believed
to resemble aging in human cells which lack telomerase
except in a restricted number of cell types. Telomerase is
activated in a wide variety of tumors and is believed to be
essential for the immortality of cancer cells. Both groups
found that this protein is expressed in immortal cell lines but
not in cell lines with a limited life span.
One of the groups (Cell paper)
established a strong
correlation between the expression of the telomerase
catalytic subunit (hEST2 or hTRT) and tumor formation.
They detected expression of this protein in all eleven
tumor samples that they examined from two different types
of tumors. They also correlated hEST2 expression with
telomerase enzymatic activity which means that
expression of this component may be the rate limiting
step in telomerase activation.
The significance of the cloning of this gene is that an
inhibitor
specific for telomerase promises to be an effective general
anti-cancer drug. It may be that telomerase is the Achille's
heel of cancer and characterization of this enzyme has the
potential to yield promising new cancer therapies. The two
companies to watch in this area are Merck and Geron.
1. Science (August 15, 1997) Volume 277,
Pages 955-959.
2. Cell (August 22, 1997) Volume 90, Pages 785-795.