Figure 3

The cTnI promoter GATA motifs are target for a protein complex in nuclear extracts from C2C12 muscle cells. A ³²P-labeled probe encompassing the two distal GATA elements in the cTnI promoter (see Table 1) shows a major retarded complex (arrow) when incubated with nuclear extracts from cultured C2C12 muscle cells (lane 1). For competition assays, the following non-radioactive competitors were added to the reaction mixture at 50- and 100- molar excess prior to the addition of the probe: self competitor (lane 2, 100-fold molar excess), CACA mutated cTnI GATA motifs (lanes 3 and 4), GCCA mutated cTnI GATA motifs (lanes 5 and 6), and a GATA sequence from the BNP promoter (lanes 7 and 8). The formation of the complex is prevented by the cTnI and BNP GATA sequences but is unaffected by the mutated cTnI GATA sequences.