Figure 4.

C/EBPβ Directly Activates PGC-1α Transcription

A, Cotransfection of baby hamster kidney cells with C/EBPβ and pGL3-PGC-1α containing 3.1-kb region of the PGC-1α promoter results in dose-dependent increase in luciferase activity. Mutations of the C/EBPβ binding site at −765/−752 (C/EBPβ mut) decreases C/EBPβ-dependent transcriptional activation. Mutation of the CRE site in the PGC-1α at −143/−135 (PGC CRE mut) did not block C/EBPβ activation of the PGC-1α promoter. ***, P value < 0.001 compared with pcDNA control; ###, not significantly different from pcDNA control (n =3). B, EMSA demonstrates that C/EBPβ contained in mouse liver nuclear extract (NE) binds to a ³²P-labeled oligonucleotide encoding the C/EBP site mutated in A. In supershift experiments, α-C/EBPβ shifts the band identified by arrow. Increasing amounts of an unlabeled consensus (cons) C/EBP sequence or the PGC-1α C/EBP site compete with the labeled probe. Mutated PGC-1α C/EBP (mut cons) site does not compete with labeled probe.