Interaction between GATA and the C/EBP Family of Transcription Factors Is Critical in GATA-Mediated Suppression of Adipocyte Differentiation

Abstract

We have previously demonstrated that GATA-2 and GATA-3 are expressed in adipocyte precursors and control the preadipocyte-to-adipocyte transition. Constitutive expression of both GATA-2 and GATA-3 suppressed adipocyte differentiation, partially through direct binding to the peroxisome proliferator-activated receptor ␥ (PPAR␥) promoter and suppression of its basal activity. In the present study, we demonstrate that both GATA-2 and GATA-3 form protein complexes with CCAAT/enhancer binding protein ␣ (C/EBP␣) and C/EBP␤, members of a family of transcription factors that are integral to adipogenesis. We mapped this interaction to the basic leucine zipper domain of C/EBP␣ and a region adjacent to the carboxyl zinc finger of GATA-2. The interaction between GATA and C/EBP factors is critical for the ability of GATA to suppress adipocyte differentiation. Thus, these results show that in addition to its previously recognized function in suppressing PPAR␥ transcriptional activity, interaction of GATA factors with C/EBP is necessary for their ability to negatively regulate adipogenesis.Adipocyte differentiation is a process controlled by multiple regulators, principally the CCAAT/enhancer binding protein (C/EBP) family of transcription factors and the peroxisome proliferator-activated receptor ␥ (PPAR␥), a nuclear hormone receptor (12, 15). Upon hormonal stimulation, the expression of C/EBP␤ and C/EBP␦ temporally increases (3), followed by expression of PPAR␥ and C/EBP␣ (3, 16). A cooperative interaction between PPAR␥ and C/EBP␣ drives the expression of genes that are necessary for the generation and maintenance of the adipogenic phenotype, such as genes producing morphological changes, lipid accumulation, and insulin sensitivity (22).The C/EBP family of transcription factors contains a highly conserved basic leucine zipper domain (bZip) that mediates homo-or heterodimerization with other isoforms in this protein family. Gain-or loss-of-function studies of preadipocyte cell lines and loss-of-function experiments in vivo all indicate that C/EBP␣ is a key regulator of adipogenesis (6,20,23,25). Furthermore, two other members of this family, C/EBP␤ and C/EBP␦, are also highly expressed in adipose tissue and have been demonstrated to be vital components of the signaling cascade which initiates adipocyte differentiation (13). Clearly, the coordinated activity of these three members of the C/EBP family makes key contributions to adipogenesis.We have previously demonstrated that the zinc finger transcription factors GATA-2 and GATA-3 are expressed predominantly in white and not brown adipose tissue in vivo and that their expression is restricted to preadipocytes and down-regulated upon adipocyte differentiation. Constitutive expression of both GATA-2 and GATA-3 suppressed adipocyte differentiation and trapped cells at the preadipocyte stage, as found when morphology and gene expression were assessed. This effect was mediated, at least in part, through direct binding of PPAR␥ and inhibition of its basal promoter activity. However, ...

Genetic variations in regulatory pathways of fatty acid and glucose metabolism are associated with obesity phenotypes: a population-based cohort study

“…Indeed, at least two members of the GATA family, GATA2 and 3, have been functionally implicated as gate keepers at the onset of adiposite differentiation, requiring GATA expression to be down-regulated. 58 In conclusion, in our explorative study among 3575 participants of a large population-based cohort, we detected five SNPs strongly associated with obesity phenotypes. Findings from genome-wide association or candidate gene studies support the potential role of the NR1H4, SIRT1, SMARCA2 and IL6 gene in obesity.…”

Adipogenesis

“…In support of this hypothesis, GATA2-deficient embryonic stem cells exhibit an enhanced differentiation potential and ectopic expression of GATA2 partially reduces fat cell development by directly binding to a PPARg promoter region to repress basal activity (Tong et al 2000). GATA2 and -3 can also associate with C/EBPa and -b to disrupt their transcriptional activity (Tong et al 2005), suggesting that GATA can attenuate adipogenesis via multiple pathways. GATA proteins can be regulated posttranslationally by acetylation, SUMOylation, and phosphorylation (Boyes et al 1998;Chun et al 2003;Menghini et al 2005).…”

Transcription factor PU.1 is expressed in white adipose and inhibits adipocyte differentiation

“…5A). Constitutive GATA2 expression effectively inhibits adipocyte differentiation (40,42). Coexpression of GATA-2 and PU.1 further inhibits adipogenesis.…”

“…GATA-2 determines peripheral blood cell linage development from hematopoietic stem cells (24), whereas GATA-3 is essential for the differentiation of type 2 T-helper lymphocytes (21,49). GATA-2 and GATA-3 also negatively regulate adipocyte differentiation (40,42). Constitutive expression of either GATA factor results in an inhibition of adipogenesis.…”

“…Constitutive expression of either GATA factor results in an inhibition of adipogenesis. The inhibition is mediated by GATA's repression on the promoters of PPAR␥ and C/EBP␣ genes and by an inhibitory protein-protein interaction between GATA and C/EBP transcription factors (40,42).…”