Reduction of CREBBP in S17 cells decreases their ability to support HSCs. (A) Representative Western blot of CREBBP protein in S17 cells after infection with a lentivirus encoding either a control shRNA (Egfp shRNA) or an shRNA targeted at Crebbp (Crebbp shRNA). TATA box-binding protein (TBP) was used as a loading control. The bar graph below shows the quantification of CREBBP levels from 3 independent experiments ± SEM. The value of the control cell line (Egfp shRNA) was set at 1. (B) Relative number of CFCs produced by wild-type LT-HSCs cocultured on S17 cells infected with a lentivirus containing Egfp-shRNA or Crebbp-shRNA. The number of CFCs produced after 6 weeks of coculture on the S17 control cell line was set at 1. Data represent means from 3 independent experiments ± SEM (*P = .045).