FIGURE 7.

C/EBPβ DNA binding activity increases in hypertrophic failing hearts. Nuclear (Nuc) and cytoplasmic (Cyto) protein fractions were isolated from the hearts of transgenic mice with cardiac-specific expression of a constitutively active calcineurin transgene (CnA*) and wild type (WT) littermates (A) or from sham operated and sTAC mice 1 week after banding (C). Western blot analysis for C/EBPβ indicated an increase in nuclear C/EBPβ in both models of heart failure. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and lamin A/C were used to verify enrichment of cytoplasmic and nuclear fractions, respectively. B and D, Western blot analysis for RCAN1 shows increased levels of the RCAN1–4 isoform in both models. E, nuclear extracts from sham sTAC and CnA* hearts were used for EMSA using the C/EBPβ consensus template, 2C, or 3A from the human RCAN1–4 promoter. F, ChIP assays using C/EBPβ-specific antibodies indicate increased occupancy of the Rcan1–4 promoter in the hearts of mice subjected to sTAC compared with sham controls. Error bars indicate S.D.