Regulation of telomerase activity in camptothecin-induced apoptosis of human leukemia HL-60 cells.
OBJECTIVE
To explore the regulation of telomerase activity in camptothecin induced apoptosis of human leukemia HL-60 cells.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Jiang
J F
JF
Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 200031, China.
Liu
W J
WJ
Ding
J
J
D017209:Apoptosis / Q000187:drug effects*; D002166:Camptothecin / Q000494:pharmacology; D015536:Down-Regulation; D019254:Genes, bcl-2; D018922:HL-60 Cells / Q000201:enzymology / Q000473:pathology; D006801:Humans; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D019098:Telomerase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
D012333:RNA, Messenger; D019098:Telomerase; D002166:Camptothecin