Supplemental methods Cell lines and cell culture AML cell lines were obtained from the ATCC and were maintained in growth media supplemented with 10% FBS (Gibco) and penicillin/streptomycin: MV4;11, K562, HEL and HL-60 in RPMI; OCI- AML3 in alpha-MEM (Gibco, Cat. No. 11875-093 and 12571-063 respectively). Factor Dependent Myeloid (FDM) cells were generated from wild-type (wt) or knockout mice as previously described (Ekert, JBC 2004) and maintained in DMEM (Invitrogen, Cat. No. 11995-065) with 10% FBS, penicillin/streptomycin and 0.5ng/mL murine IL-3 (R&D Cat. No. 403-ML-010). All cell lines were mycoplasma free at the time of experiments. All cell cultures were incubated at 37∘C at 5% CO2. SDS-PAGE immunoblotting. Protein lysates were generated using NP-40 lysis buffer (10mM Tris-HCl, pH 7.4, 137mM NaCl, 10% glycerol, 1% NP-40) supplemented with PMSF, the cOmplete protease inhibitor cocktail (EDTA-free, Roche, Cat No. 11 836 170 001, 1x) and PhosSTOP phosphatase inhibitor cocktail (Roche Cat. No. 04 906 845 001, 1x). Proteins were separated using sodium dodecyl sulfate polyacrylamide gel electrophoresis, and transferred onto nitrocellulose (Amersham Hybond) or PVDF membranes (Immobilon, Millipore). Membranes were blocked in skim milk, BSA or Odyssey blocking buffer (Li-Cor) and probed overnight with a 1:1000 dilution anti-BCL-2 monoclonal antibody (mAb)(clone Bcl-2-100, WEHI), anti-MCL-1 mAb (clone 19C4-15, WEHI), anti-BCL-xL mAb (clone 44/Bcl-x, BD Transduction Lab), anti-BAX mAb (clone 21C10-23, WEHI), anti-BAK mAb (clone 8F8, WEHI), anti-BIM mAb (clone 3C5, WEHI), anti-p53 mAb (clone 1C12, Cell Signaling Technology), anti-GAPDH-HRP mAb (Cell Signaling Technology), antiphospho-CTD-RNA Polymerase II mAb (Cell Signaling Technology) or anti-tubulin mAb (Sigma-Aldrich). Filters were then washed, probed with either anti-mouse HRP, anti-rabbit HRP (Dako) or anti-rat HRP (Souther Biotech) secondary antibodies. Signals were developed using Supersignal chemiluminescent substrates (Thermo Scientific) or visualized using the Odyssey Infrared Imaging System, (LI-COR). RT-PCR The generation of cDNA was accomplished by the use of Superscript III Reverse Transcriptase (Invitrogen Catalogue No. 18080044). Commercial primers for Noxa (Pmaip1, TaqMan Cat. # 4331182) and Puma (Bbc3, TaqMan Cat. # 4331182) were used; the real-time PCR was run on the Roche LightCycler 480. The results were normalized to a housekeeper gene (HGPRT or GAPDH).