Influence of 3'-azido-2',3'-dideoxyguanosine treatment on amounts of TERT and POT1 in human HL60 cells.

In human cells, TERT (telomerase reverse transcriptase) is involved in the synthesis of telomere DNA, and POT1 (protection of telomeres 1) is believed to be a regulator of telomere length. We have reported that long-term treatment of human HL60 cells with 50 microM 3'-azido-2',3'-dideoxyguanosine (AZddG) caused telomeres to shorten significantly during early passages (up to 40-50 days), but that telomere length was then stabilized at approximately 2 kbp during later passages. Additionally, cell growth rates showed no obvious change during culture in the presence of 50 microM AZddG. Western blot analysis of these cells showed that the amounts of TERT and POT1 expressed were increased significantly and slightly, respectively. Furthermore, telomeric 3' G-overhangs (G-tails) of AZddG-treated cells were lengthened. These findings suggest that HL60 cells may develop resistance to telomere erosion induced by AZddG.