Fig. 6. Electromobility shift and supershift assays of the slow MyHC2 NFAT binding site. (A) Nuclear extracts from innervated (SC) and noninnervated PM (lanes 2-5) and MA (lanes 6-9) muscle fibers incubated in control medium or medium containing 100 µM ryanodine (Ry) were incubated with the NFAT binding site oligonucleotide probe. Protein-DNA complexes were resolved in 5% nondenaturing polyacrylamide gel. A specific protein-DNA complex (arrowhead) formed from extracts of innervated PM muscle fibers incubated in medium containing ryanodine (lane 5) and from extracts of innervated MA muscle fibers (lanes 8 and 9). Lane 1 contained no nuclear extract. A faster migrating protein-DNA complex (asterisk) of unknown composition was present in each lane. (B) Inclusion of an anti-NFATc1 antibody in the binding reaction resulted in a supershifted protein-DNA complex (arrow). An anti-MEF2a antibody did not yield a supershifted complex.