Context-dependent transcriptional cooperation mediated by cardiac transcription factors Csx/Nkx-2.5 and GATA-4

Although the cardiac homeobox gene Csx/Nkx-2.5 is essential for normal hear t development, little is known about its regulatory mechanisms. In a search for the downstream target genes of Csx/Nkx-2.5, we found that the atrial n atriuretic peptide (ANP) gene promoter was strongly transactivated by Csx/N kx-2.5. Deletion and mutational analyses of the ANP promoter revealed that the Csx/Nkx-2.5-binding element (NKE2) located at -240 was required for hig h level transactivation by Csx/Nkx-2.5. We also found that Csx/Nkx-2.5 and GATA-4 displayed synergistic transcriptional activation of the ANP promoter , and in contrast to previous reports (Durocher, D., Charron, F., Warren, R ., Schwartz, R. J., and Namer, M. (1997) EMBO J. 16, 5687-5696; Lee, Y., Sh ioi, T., Kasahara, H., Jobe, S. M., Wiese, R. J., Markham, B., and Izumo, S (1998) Mel; Cell. Biol. 18, 3120-3129), this synergism was dependent on bi nding of Csx/Nkx-2.5 to NKE2, but not on GATA-4-DNA interactions. Although GATA-4 also potentiated the Csx/Nkx-2.5-induced transactivation of the arti ficial promoter that contains multimerized Csx/Nkx-2.5-binding sites, Csx/N kx-2.5 reduced the GATA-4-induced transactivation of the GATA-4-dependent p romoters. These findings indicate that the cooperative transcriptional regu lation mediated by Csx/Nkx-2.5 and GATA-4 is promoter context-dependent and suggest that the complex cis-trans interactions may fine-tune gene express ion in cardiac myocytes.