ACTIVATION OF TELOMERASE IN HUMAN-LYMPHOCYTES AND HEMATOPOIETIC PROGENITOR CELLS

This is the first report describing up-regulation of telomerase activi ty in human normal cells. Telomerase, a ribonucleoprotein enzyme, has been thought to be involved in maintaining telomere length stability i n germline and most cancer cells, but not in normal cells. However, in the present study, we demonstrate that telomerase activity is detecta ble at low levels in normal human T and B cells, increases by in vitro mitogenic stimulation, increases in hematopoietic progenitor cells up on their proliferation and differentiation, and decreases with aging. Understanding the regulation of telomerase activity in normal cells ma y provide important insights not only into the mechanisms of normal ce llular senescence but also into the mechanisms of telomerase activity deregulation as part of cancer development.