HeLa Kyoto Cell Culture and Transfection

The cervical cancer cell line HeLa Kyoto, a gift from Heinrich Leonhardt (LMU Munich, Munich, Germany), was grown in Dulbecco’s Modified Eagle’s Medium (DMEM, Thermo Fisher Scientific, Waltham, MA, USA) supplemented with 10% heat-inactivated fetal bovine serum (FBS, Thermo Fisher Scientific) and 1% penicillin/streptomycin (Thermo Fisher Scientific), in a humidified atmosphere, at 37 °C and 5% CO₂. HeLa Kyoto cells stably expressing enhanced green fluorescence protein (GFP), GFP-tagged H2A or GFP-tagged histone variants (H2A.X, H2A.Bbd and H2A.Z.1) were cultured as described [16 (link),19 (link)]. Transient transfections of HeLa Kyoto cells with GFP, GFP–JAZF1 or GFP–Tip60 were performed by using X-tremeGENE HP (Roche, Basel, Switzerland) or FuGENE HD (Promega, Madison, WI, USA) according to the manufacturer’s instructions. Two days after transfection, cells were harvested for several experimental applications. Expression levels of stably or transiently transfected HeLa Kyoto cells were quantified by using a FACSCanto machine (Becton Dickinson, Franklin Lakes, NJ, USA) or a BD Accuri C6 Plus Flow Cytometer (Becton Dickinson). Cells were routinely tested for mycoplasma contamination.