Figure 3.

CST inhibits telomerase initiation. (A) Direct assay with telomerase immunopurified from HeLa cells, unlabeled 10 nM 3xTEL DNA primer, and nucleotides including [³²P]dGTP. LC1, LC2 and LC3 are oligonucleotides added as loading controls. (B) Radioactivity incorporated into telomerase products as a function of reaction time. (C) Telomerase assay for 1 h with the DNA primer pre-incubated with WT CST at the concentrations shown. (D) Counts incorporated into telomerase products normalized to the counts incorporated in the absence of CST. Data from two technical replicates included and fit to Equation (3). (E) Dependence of IC₅₀ on the concentration of 3xTEL DNA in the reaction. Parentheses on last data point indicate that it is underdetermined, because only partial inhibition was achieved at the highest CST concentration.