Original Article

Regulation of telomerase activity in camptothecin-induced apoptosis of human leukemia HL-60 cells

Authors: Jian-Fei Jiang, Wei-Jun Liu, Jian Ding


To explore the regulation of telomerase activity in camptothecin induced apoptosis of human leukemia HL-60 cells.
Apoptosis of HL-60 cells was induced by camptothecin (1 mg/L) for 2, 4, and 6 h. Apoptosis was determined by agarose electrophoresis and flow cytometry analysis. To assess telomerase activity, a PCR-based telomeric repeat amplification protocol assay (TRAP) was used. RT-PCR was performed to examine the mRNA levels of hTR (human telomerase RNA component), hEST2/hTERT (human telomerase reverse transcriptase), TLP1/TP1 (telomerase association protein 1), and bcl-2 (B cell leukemia/lymphoma 2 gene) in HL-60 cells before and after camptothecin treatment.
Telomerase activity was decreased in a time-dependent manner during the camptothecin induced apoptosis of HL-60 cells. However, no difference in expression of each telomerase subunit was detected, while expression of bcl-2 was progressively down-regulated.
These lines of evidences indicated that down-regulation of the telomerase activity in HL-60 cells was closely related to camptothecin-induced apoptosis, and the telomerase activity was not blocked at the transcriptional levels of the genes of the known ribonucleoprotein (RNP) complex components. We also found that bcl-2 did not regulate the mRNA expressions of telomerase subunits directly."

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