title: GATA-4 and Nkx-2.5 coactivate Nkx-2 DNA binding targets: role for regulating early cardiac gene expression.
abstract: The cardiogenic homeodomain factor Nkx-2.5 and serum response factor (SRF) provide strong transcriptional coactivation of the cardiac alpha-actin (alphaCA) 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 alphaCA 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, alphaCa 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.
authors.affiliation: Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Sepulveda
authors.forename: N
authors.initials: N
authors.lastname: Belaguli
authors.forename: V
authors.initials: V
authors.lastname: Nigam
authors.forename: C Y
authors.initials: CY
authors.lastname: Chen
authors.forename: M
authors.initials: M
authors.lastname: Nemer
authors.forename: R J
authors.initials: RJ
authors.lastname: Schwartz
mesh_terms: D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D002874:Chromosome Mapping; D004247:DNA / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D050991:GATA4 Transcription Factor; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D006321:Heart / Q000196:embryology*; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins / Q000378:metabolism*; D008648:Mesoderm / Q000378:metabolism; D008956:Models, Chemical; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D017384:Sequence Deletion; D026362:Serum Response Factor; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D029867:Xenopus Proteins; D016335:Zinc Fingers
chemical_list: D004268:DNA-Binding Proteins; D050991:GATA4 Transcription Factor; D000072576:Homeobox Protein Nkx-2.5; D018398:Homeodomain Proteins; C095552:NKX2-5 protein, human; D009687:Nuclear Proteins; D026362:Serum Response Factor; D014157:Transcription Factors; D029867:Xenopus Proteins; D004247:DNA