In vitro adipogenesis. (A) NIH 3T3 cells, transduced with retroviruses from Phoenix-E cultures transfected with either pBabePuro (Con) expressing C/EBPα (WT) or C/EBPαΔPHR (ΔPHR), were allowed to differentiate into adipocytes. Northern blot analysis used probes against the late adipogenic marker aP2 and 18S rRNA (for normalization). The numbers below the blots indicate the extent of differentiation relative to the wild type (derived from two independent sets of experiments). (B) Western blot analysis of the cultures from panel A probed with a C/EBPα-specific antibody. An α-tubulin antibody was used to control for even loading. (C) HEK293S cells were transiently transfected with the 1-μg reporter (pTK81-4xC/EBPwtLuc) and internal control (pcH110) and increasing amounts (10, 20, and 30 ng) of either pcDNA3-C/EBPα (WT) or pcDNA3-C/EBPαΔPHR (ΔPHR). After approximately 48 h, luciferase activities were measured and normalized to the internal β-galactosidase control. Each value represents the average of two independent experiments. Error bars indicate standard deviations.