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To test the role of poly(ADP-ribose) polymerase on the telomerase activity, we determined the telomerase activity in leukemic cells K562 treated with benzamide and 4-amino 1,8 naphthalimide (NAP), the inhibitors of PARP. We observed that both the agents inhibited telomerase activity in a dose-dependent manner. The doses of benzamide and NAP that inhibited telo-merase activity to 50% of untreated control cells were 10.7 ± 0.6 mmand 200 ± 7lm, respectively. | ềFEBS Journal Benzamide and 4-amino 1 8 naphthalimide treatment inhibit telomerase activity by down-regulating the expression of telomerase associated protein and inhibiting the poly ADP-ribosyl ation of telomerase reverse transcriptase in cultured cells Utpal Ghosh and Nitai P. Bhattacharyya Crystallography and Molecular Biology Division Saha Institute of Nuclear Physics Calcutta India Keywords 4-amino 1 8 naphthalimide benzamide poly ADP-ribosyl ation TEP1 TP1 TERT Correspondence N. P. Bhattacharyya Crystallography and Molecular Biology Division Saha Institute of Nuclear Physics 1 AF Bidhan Nagar Calcutta 700 064 India Fax 91 033 2337 4637 Tel 91 033 2337 5345-49 E-mail nitai@petal.saha.ernet.in or nitai_sinp@yahoo.com Received 14 May 2005 revised 10 June 2005 accepted 28 June 2005 doi 10.1111 j.1742-4658.2005.04837.x To test the role of poly ADP-ribose polymerase on the telomerase activity we determined the telomerase activity in leukemic cells K562 treated with benzamide and 4-amino 1 8 naphthalimide NAP the inhibitors of PARP. We observed that both the agents inhibited telomerase activity in a dosedependent manner. The doses of benzamide and NAP that inhibited telomerase activity to 50 of untreated control cells were 10.7 0.6 mM and 200 7 pM respectively. Benzamide treatment 10 mM inhibited telomerase activity in a time-dependent manner. We also tested the ability of benzamide to inhibit the telomerase activity in Chinese hamster V79 cells and observed similar inhibition of the telomerase activity. Expression of telomerase reverse transcriptase TERT and telomerase RNA component detected by RT-PCR remained unaltered by treatment with benzamide or NAP. On the contrary the expression of telomerase associated protein TEP1 TP1 as detected by RT-PCR and western blot analysis was reduced by both the agents. Further in K562 cells immunoprecipitation with the anti-TERT IgG and probed anti-poly ADP-ribose IgG revealed that TERT was poly ADP-ribosyl ated in the .
