IMiD compounds induce the degradation of the IKZF1 protein in human CD34⁺ cells. Immunoblot analysis of IKZF1 or β-actin in CD34⁺ cells was performed in (A) CD34⁺ cells treated with DMSO (0.01%) or POM (1 μM) for 1 hour before the addition of cycloheximide (CHX; 100 μg/mL) for the indicated times; CD34⁺ cells treated with POM at the indicated concentrations with or without (B) MG132 (10 μM) and (C) MLN4924 (1 μM) for 24 hours; (D) CD34⁺ cells treated with DMSO (0.01%), LEN or POM (1 μM), with or without PS341 (10 nM) for 24 hours. (E) For the analysis of the ubiquitination of IKZF1, CD34⁺ cells were treated with MG132 (10 μM) and DMSO (0.02%), LEN, or POM (2 μM) for 2 hours. Immunoprecipitation was performed using an IKZF1 antibody, followed by western blotting with an ubiquitin antibody, indicating the protein pulled down by the IKZF1 antibody (right). (Left) Five percent total protein input.