Id1 protein levels are increased after expression of active C/EBPα.

(A) Human CD34⁺ cells transduced with MIGR1 or MIGR1 C/EBPα-ER, were sorted for the expression of GFP and treated with β-estradiol (+) or ethanol (−) for 16 hours. Immunofluorescence was performed using an α-Id1 antibody and counter stained with DAPI to identify the nucleus (original magnification, × 600). (B) Cells sorted for GFP expression and treated for 16 hours with β-estradiol or ethanol were analyzed for expression of Id1 protein by Western blot analysis using an α-Id1 antibody. The control lane contains cell lysate from 3T3 cells. The level of α-tubulin expression is indicated, to control for equal protein loading.