Upstream stimulatory factors regulate the C/EBP alpha gene during differentiation of 3T3-L1 preadipocytes.
During adipocyte differentiation, CCAAT/enhancer-binding protein alpha (C/EBPalpha) functions as a pleiotropic transcriptional activator of numerous adipocyte genes. The promoter of the C/EBPalpha gene has an E-box upstream of C/EBP binding site. Deletion or mutation of the E-box decreases promoter activity, suggesting that the E-box participates in the regulation of C/EBPalpha expression. Protein binding to the E-box during the adipocyte differentiation is increased as indicated by EMSA and UV cross-linking. Purification of the E-box binding proteins from differentiated 3T3-L1 adipocytes, showed that USF and AP-4 are associated with the E-box. Supershift analysis showed that USF1 and USF2 bind to this element as heterodimers, whereas the addition of anti-AP-4 antibody enhanced the binding complex, suggesting that AP-4 negatively regulates the promoter activity. The expression of AP-4 is reciprocally regulated with USF-1 during adipocyte differentiation. These findings suggest that USF-1 and 2 play roles in C/EBPalpha expression, whereas the AP-4 represses it.
Kim
Jae-woo
JW
Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Monila
Henrik
H
Pandey
Akhilesh
A
Lane
M Daniel
MD
D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology* / Q000378:metabolism; D000818:Animals; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000096:biosynthesis / Q000235:genetics*; D002454:Cell Differentiation / Q000235:genetics*; D024721:E-Box Elements / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology*; D051379:Mice; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000502:physiology; D012097:Repressor Proteins / Q000502:physiology; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism; D051720:Upstream Stimulatory Factors / Q000502:physiology*
D022763:CCAAT-Enhancer-Binding Protein-alpha; D012097:Repressor Proteins; D051720:Upstream Stimulatory Factors; C515558:Zfp668 protein, mouse