Removal of IL-2 from HTLV-I–immortalized cells decreases telomerase activity. (A) Total cell extracts from IL-2–independent (MT2 and MT4) and IL-2–dependent (LAF and 1185) cell lines were immunoblotted with anti-Tax. Actin served as a loading control. (B) LAF and 1185 cells were cultured in the presence (+) or absence (−) of IL-2 for 24 hours, followed by TRAP analysis for telomerase activity. TPGs are calculated as the percentage of activity compared with cells grown with IL-2 (100%), as previously reported.9 Results are representative of at least 2 independent experiments, and standard deviation (SD) is indicated. (C) LAF cells were analyzed at either 4 hours or 24 hours after growth in either IL-2–containing or IL-2–deprived media. For each time point, cells were collected and analyzed by FACS for cell-cycle and TRAP for telomerase activity. TPGs were calculated as the percentage of activity compared with cells grown with IL-2 (100%).
