a, Whole-cell extracts from 293 HEK cells stably expressing empty vector (Ctrl), wild-type Myc-tagged TRF2 (WT), phospho-dead mutant TRF2S367A (S/A), or phospho-mimetic mutants of Myc-TRF2S367D and Myc-TRF2S367E (S/D and S/E) were immunoprecipitated with anti-Myc antibody or normal mouse IgG. Protein complexes were analysed with antibodies against Rap1, TRF1, and Myc. b, 4-OHT-Cre-TRF2F/F MEFs expressing wild-type (WT) or phospho-dead (S/A) mutant of TRF2 were transfected either with control siRNA (NTC) or siRNA against RAP1. Whole-cell extracts were analysed 72 hours later as indicated. c, Quantitation (left panel) and representative images (right panels) of chromosome fusions in the TRF2F/F MEFs depicted in (b) performed 96hr after 4-OHT treatment. (one-way ANOVA, mean ± SEM; n=30 metaphases analysed). In a - d the experiments were independently repeated at least two times with similar results.