FIG. 5.

Human telomerase is recruited to telomeres via the OB-fold of TPP1. (A) Immunoblot analysis of ectopically expressed FLAG epitope-tagged full-length TPP1 (TPP1), FLAG-tagged, shRNA-resistant full-length TPP1 (TPP1*), and FLAG-tagged, shRNA-resistant TPP1 lacking the OB-fold (TPP1ΔOB*). Super-telomerase HeLa cells were cotransfected with the indicated plasmids, and protein expression was analyzed 4 days after transfection. Black arrowheads indicate the presence of the respective TPP1 proteins, and white arrowheads indicate the lack of expression. Immunoblots were probed with anti-TPP1, anti-FLAG and CENP-A antibodies as indicated. (B) ChIP of telomeric and Alu DNA with hTERT antibody from cells in panel A. (C) Quantification of data in panel B representing percentage of telomeric and Alu DNA recovered in hTERT ChIP. Error bars correspond to standard deviations of results of four independent experiments. Statistical analyses were done using a two-tailed Student's t test (*, P < 0.05).