Cell Line Cultivation Protocol

The following cell lines were used in this study: human fetal foreskin fibroblast cells immortalized with human telomerase (HFFF-TERTs; male)^{53 (link)}, HeLa (American Type Culture Collection (ATCC) CCL-2), HEK293T (ATCC CRL-11268), T-REx-293 (Life Technologies), BS-C-1 (ATCC CCL-26) and RK13 (ATCC CCL-37). All cell lines were cultured in DMEM (Gibco), supplemented with 10% FBS (PAN Biotech) and 50 μg ml⁻¹ penicillin–streptomycin (Gibco). T-REx-293-derived cells that were stably transfected with pcDNA4/TO plasmids were further supplemented with 10 μg ml⁻¹ blasticidin (Thermo Fisher) and 100 μg ml⁻¹ zeocin (Gibco). HEK293T cells that were transduced to overexpress Myc-tagged proteins^{10 (link)} were supplemented with 1 μg ml⁻¹ puromycin (Invivogen). A complete list of cell lines is described in Supplementary Table 1.