Figure 4 Troponin C1, slow skeletal and cardiac type (TNNC1) was negatively regulated by forkhead box 03 (FOXO3). (A) Schematic diagram of the FOXO3 binding sites on the promoter of TNNC1. The expression of TNNC1 in A549 cells transfected with an empty vector (Scramble) or FOXO3 overexpression plasmid (FOXO3-over) was determined by reverse tracscription-quantitative polymerase chain reaction (B, C) or western blot (D). Dual-luciferase reporter assay was used to analyze the TNNC1 promoter activity. The promoter constructs were cotransfected with empty vector (Vector) or FOXO3 overexpression plasmid (FOXO3). (E) Luciferase level was significantly attenuated after the cotransfection of TNNC1 promoter with FOXO3 plasmid compared with the vector plasmid.