WM35 (laboratory of Joyce Slingerland) and CCRF-CEM-C7H2 (CEM) (laboratory of Reinhard Kofler) cells were grown in RPMI (Sigma-Aldrich, St. Louis, MO, USA), 10% fetal calf serum (FCS; PAA, Pasching, Upper Austria, Austria), penicillin/streptomycin (Sigma-Aldrich). HeLa, HeLa T-REx (Invitrogen, Carlsbad, CA, USA), MDA-MB-231 (laboratory of Stephan Geley) and MEFs (laboratory of Nisar Malek) were cultured in Dulbecco's modified Eagle media (Sigma-Aldrich), 10% FCS (PAA), penicillin/streptomycin. Cells were irradiated in a UV Stratalinker 1800 (Stratagene, La Jolla, CA, USA). Cells were lyzed in Laemmli buffer80 (link) or IP-buffer81 (link) using an ultrasonic homogenizer (Sonoplus, Bandelin, Berlin, Germany). Subcellular fractionation was performed as previously described.31 (link) Thymocytes were isolated from the thymus of a 4-week-old male C57BL/6 mouse using a sterile cell strainer (#352360, BD, Heidelberg, Germany). Single cells were grown in RPMI (Sigma-Aldrich), 10% FCS (PAA), 50 μM β-mercaptoethanol (Sigma-Aldrich), 1 mM pyruvate (Gibco Life Technologies, Carlsbad, CA, USA), penicillin/streptomycin (Sigma-Aldrich) with or without dexamethasone (10−7 M).