Figure 3.
Upstream regulatory elements of the myoglobin gene participating in calcineurin-dependent transactivation. Data are presented as reporter–gene expression (mean ± s.e.m. of six independent transfections) normalized to activity of a cotranfected CMV–lacZ plasmid [luminometer units (×105)/well (1.9 × 105 cells)]. (A) Responses of native (Mb380) or mutated variants of a truncated segment (−373 to +7) of the human myoglobin gene promoter to activated calcineurin. Nucleotide substitutions were introduced into each of two upstream regulatory elements shown previously to be essential for muscle-specific promoter activity (Devlin et al. 1989; Bassel-Duby et al. 1993; Grayson et al. 1995, 1998). These mutated promoters (MbΔA/T and MbΔCCAC) are likewise defective for calcineurin-stimulated transactivation. (Stippled box) −CnA*; (solid bars) +CnA*. (B) Responses to activated calcineurin of synthetic promoters constructed with various combinations of multimerized oligonucleotide cassettes representing protein-binding motifs (CCAC) Sp1 binding site; (A/T) MEF2 binding site; (NRE) putative NFAT binding site; (TATA) TBP binding site and core promoter from the myoglobin promoter.