ABSTRACT
The development of mature adipocytes from preadipocyte precursor cells requires coordinated changes in gene expression. Management of these expression changes relies on the actions of both DNA-binding transcription factors and their coregulators. Recent studies have identified the corepressor C-terminal binding protein (CtBP) as a key transcriptional coregulator in adipose tissue. CtBP proteins work with several different partner proteins to regulate the development of both white and brown adipocytes. CtBP is of particular interest as it binds to NAD(+)/NADH and may respond to the metabolic state of the cell, thereby linking changes in nutrient levels to transcriptional outcomes.
Subject(s)
Adipogenesis , Alcohol Oxidoreductases/metabolism , DNA-Binding Proteins/metabolism , 3T3-L1 Cells , Alcohol Oxidoreductases/chemistry , Alcohol Oxidoreductases/genetics , Animals , DNA-Binding Proteins/chemistry , DNA-Binding Proteins/genetics , Gene Expression Regulation , Metabolic Diseases/metabolism , Metabolic Diseases/therapy , MiceABSTRACT
GATA transcription factors have been implicated in controlling adipogenesis in Drosophila and in mammals. In mammals, both GATA2 and GATA3 have been shown to be present in preadipocytes, and their silencing allows the onset of adipogenesis. Overexpression of GATA proteins blocks adipogenesis in cellular assays. GATA factors have been found to operate through recruiting cofactors of the Friend of GATA (FOG) family. FOG proteins, in turn, recruit co-regulators, including C-terminal binding proteins (CTBPs). We have investigated whether FOGs and CTBPs influence adipogenesis. We found that both FOG1 and FOG2 are expressed in cells prior to adipogenesis but are down-regulated as adipogenesis proceeds. Overexpression of FOG1 or FOG2 interferes with adipogenesis. Mutant versions of FOG2 unable to bind CTBP or GATA proteins are impaired in their inability to inhibit adipogenesis. Finally, a mutant version of GATA2, unable to associate with FOGs, also displays abnormal activity and causes enhanced cell proliferation. These results implicate FOGs and CTBPs as partners of GATA proteins in the control of adipocyte proliferation and differentiation.
Subject(s)
Adipogenesis/physiology , Alcohol Oxidoreductases/metabolism , DNA-Binding Proteins/metabolism , GATA Transcription Factors/metabolism , Nuclear Proteins/metabolism , Transcription Factors/metabolism , 3T3-L1 Cells , Alcohol Oxidoreductases/genetics , Animals , DNA-Binding Proteins/genetics , GATA Transcription Factors/genetics , Humans , Male , Mice , Mutation , Nuclear Proteins/genetics , RNA, Small Interfering/metabolism , Transcription Factors/geneticsABSTRACT
Krüppel-like factors (KLFs) recognize CACCC and GC-rich sequences in gene regulatory elements. Here, we describe the disruption of the murine basic Krüppel-like factor gene (Bklf or Klf3). Klf3 knockout mice have less white adipose tissue, and their fat pads contain smaller and fewer cells. Adipocyte differentiation is altered in murine embryonic fibroblasts from Klf3 knockouts. Klf3 expression was studied in the 3T3-L1 cellular system. Adipocyte differentiation is accompanied by a decline in Klf3 expression, and forced overexpression of Klf3 blocks 3T3-L1 differentiation. Klf3 represses transcription by recruiting C-terminal binding protein (CtBP) corepressors. CtBPs bind NADH and may function as metabolic sensors. A Klf3 mutant that does not bind CtBP cannot block adipogenesis. Other KLFs, Klf2, Klf5, and Klf15, also regulate adipogenesis, and functional CACCC elements occur in key adipogenic genes, including in the C/ebpalpha promoter. We find that C/ebpalpha is derepressed in Klf3 and Ctbp knockout fibroblasts and adipocytes from Klf3 knockout mice. Chromatin immunoprecipitations confirm that Klf3 binds the C/ebpalpha promoter in vivo. These results implicate Klf3 and CtBP in controlling adipogenesis.
