In this study, we found that Krüppel-like factor (KLF) 9 activate the progression of the early phase of adipocyte differentiation in mouse adipocytic 3T3-L1 cells. KLF9 mRNA was detected in preadipocytes; and its level increased after the initiation of adipocyte differentiation, reached its maximum at 1h, and gradually decreased thereafter. Functional suppression of KLF9 mRNA by its siRNAs repressed the accumulation of the intracellular lipids with a reduction in the expression of CCAAT/enhancer-binding protein (C/EBP) β, but not in that of C/EBPδ. In contrast, C/EBPβ and C/EBPδ did not affect the expression of KLF9 in 3T3-L1 cells. A chromatin immunoprecipitation assay revealed that KLF9 bound the KLF binding element at position -874 of the mouse C/EBPβ promoter. Moreover, the ability of KLF9 to bind to this element was enhanced, with a peak at 1-2h after the initiation of adipogenesis, whose profile well resembled that of the expression of the C/EBPβ gene in 3T3-L1 cells. These results indicate that KLF9 activated the early phase of adipogenesis by enhancing the expression of the C/EBPβ gene in 3T3-L1 cells.
Keywords: Adipocytes; Adipogenesis; C/EBP; C/EBPβ; CCAAT/enhancer-binding protein; ChIP; FAS; KLF; KLF-binding element; KLFE; Krüppel-like factor; LPL; N.C.; PPAR; SCD; SREBP; TATA-binding protein; TBP; Transcription factor; aP2; chromatin immunoprecipitation; fatty acid binding protein 4; fatty acid synthase; lipoprotein lipase; negative control; peroxisome proliferator-activated receptor; stearoyl-CoA desaturase; sterol regulatory element-binding protein.
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