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Mol Cell Biol, June 1998, p. 3405-3415, Vol. 18, No. 6
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

GATA-4 and Nkx-2.5 Coactivate Nkx-2 DNA Binding Targets: Role for Regulating Early Cardiac Gene Expression

Jorge L. Sepulveda,1,2 Narashimaswamy Belaguli,1 Vishal Nigam,1 Ching-Yi Chen,3 Mona Nemer,4 and Robert J. Schwartz1,*

Department of Cell Biology, Baylor College of Medicine,1 and Department of Pathology, Baylor College of Medicine and VA Medical Center,2 Houston, Texas 77030; Department of Pharmacology, University of California, San Diego, La Jolla, California 920933; and Laboratoire de Développement et Différentiation Cardiaques, Institut de Recherches Cliniques de Montréal, Montreal, Quebec, Canada H2W 1R74

Received 31 October 1997/Returned for modification 18 December 1997/Accepted 18 March 1998

The cardiogenic homeodomain factor Nkx-2.5 and serum response factor (SRF) provide strong transcriptional coactivation of the cardiac alpha -actin (alpha CA) promoter in fibroblasts (C. Y. Chen and R. J. Schwartz, Mol. Cell. Biol. 16:6372-6384, 1996). We demonstrate here that Nkx-2.5 also cooperates with GATA-4, a dual C-4 zinc finger transcription factor expressed in early cardiac progenitor cells, to activate the alpha CA promoter and a minimal promoter, containing only multimerized Nkx-2.5 DNA binding sites (NKEs), in heterologous CV-1 fibroblasts. Transcriptional activity requires the N-terminal activation domain of Nkx-2.5 and Nkx-2.5 binding activity through its homeodomain but does not require GATA-4's activation domain. The minimal interactive regions were mapped to the homeodomain of Nkx-2.5 and the second zinc finger of GATA-4. Removal of Nkx-2.5's C-terminal inhibitory domain stimulated robust transcriptional activity, comparable to the effects of GATA-4 on wild-type Nkx-2.5, which in part facilitated Nkx-2.5 DNA binding activity. We postulate the following simple model: GATA-4 induces a conformational change in Nkx-2.5 that displaces the C-terminal inhibitory domain, thus eliciting transcriptional activation of promoters containing Nkx-2.5 DNA binding targets. Therefore, alpha Ca promoter activity appears to be regulated through the combinatorial interactions of at least three cardiac tissue-enriched transcription factors, Nkx-2.5, GATA-4, and SRF.

* Corresponding author. Mailing address: Department of Cell Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030. Phone: (713) 798-6649. Fax: (713) 798-7799. E-mail: schwartz{at}bcm.tmc.edu.

Mol Cell Biol, June 1998, p. 3405-3415, Vol. 18, No. 6
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


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