FIGURE 5.

Sequence dependence of TPP1 OBD association with telomerase holoenzyme co-expressed in human cells. A and B, telomerase holoenzyme activity co-immunopurification with an f-tagged TPP1 OBD co-expressed with zz-TERT and hTR in human cells. Each panel of activity assays begins with a negative control that monitors holoenzyme binding in the absence of f-tagged TPP1 OBD. The bracket indicates TPP1 OBD variants with reproducibly and severely reduced co-immunopurification of holoenzyme activity; the two additional TPP1 OBD variants indicated with an asterisk reproducibly but less severely compromise holoenzyme co-immunopurification. The TPP1 OBD variants with compromised holoenzyme interaction were expressed at the same level as wild-type TPP1 (data not shown).