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 α-actin (αCA) 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 αCA 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, αCa 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.

Physical Interaction between GATA-5 and Hepatocyte Nuclear Factor-1α Results in Synergistic Activation of the Human Lactase-Phlorizin Hydrolase Promoter

“…For example, similar to the model presented here is the well characterized model for the synergistic activation of cardiac promoters by GATA-4 and Nkx2.5 (47,48,(57)(58)(59)(60), a homeodomain-containing transcription factor like HNF-1␣. In this model, the C-terminal zinc finger and basic regions of GATA-4 and the homeodomain of Nkx2.5 are required for physical association, which, in turn, is necessary for synergistic activation of several genes (47,48,57). Furthermore, intact Nkx2.5-binding sites on cardiac promoters are required for synergistic activation (47,48,57).…”

“…In this model, the C-terminal zinc finger and basic regions of GATA-4 and the homeodomain of Nkx2.5 are required for physical association, which, in turn, is necessary for synergistic activation of several genes (47,48,57). Furthermore, intact Nkx2.5-binding sites on cardiac promoters are required for synergistic activation (47,48,57). HNF-1␣ cooperatively activates the sodium-glucose transporter (SGLT1) with SP-1, a zinc finger-containing protein (44).…”

Factors controlling cardiac myosin-isoform shift during hypertrophy and heart failure

“…(iv) Factors that binds to M-CAT sequences, named TEF1 isoforms; they make a complex with SRF and MEF2 and are found to be necessary for muscle-specific expression of genes in both the cardiac and skeletal muscle-cell context. However, gene ablation of factors such as TEF1, GATA4, and Nkx2.5 has been found to have no effect on the expression of MHCs, while some proteins expressed in the cardiac muscle cell background, such as MLC2 and ANF, were found to be absent in Nkx2.5 null mice [39][40][41][42][43][44][45][46]. SRF knock-out was shown to attenuate the expression of both α-and βMHC transcripts [47].…”

GATA and Nkx factors synergistically regulate tissue-specific gene expression and development in vivo

“…Given the changes in expression of target genes to Nkx2.1, but not to Gata6, haploinsufficiency, and that Gata6 and Nkx2.1 are both associated with regions of chromatin that contain only Nkx2.1 DNA-binding sites, our data suggest that Gata6 acts as modifier of Nkx2.1 function. GATA and Nkx factors are co-expressed in several other tissues besides lung epithelium, including in myocardium and smooth muscle (Durocher et al, 1997;Lyons et al, 1995;Sepulveda et al, 1998;Sepulveda et al, 2002). Thus, our findings may have important implications for the synergy between these transcription factor families in other developmental systems.…”

“…This synergy appears to occur only in enhancer elements containing Nkx2.1 DNA-binding sites, suggesting the differential regulation and usage of such crucial protein-protein interactions. Such interactions could increase the affinity of Gata6 and Nkx2.1 for additional co-factors or could increase the affinity of the binding of Nkx2.1 to DNA, as has been suggested in Gata4-Nkx2.5 interactions (Sepulveda et al, 1998). The identification of Scd1 and Dpp4 as direct targets of Gata6-and Nkx2.1-regulation provides novel information on how these transcription factors regulate both phospholipid production and airway-epithelial homeostasis.…”