Fig. 4.

Transcriptional factor E2F1 is responsible for HBXIP-stimulated PKM promoter. a Nucleotide mutation diagram of binding sites of Sp1 and E2F1 in pGL-P2. b, c Luciferase reporter gene assay of PKM promoter activities in MCF-7 (b) and T47D cells (c). The cells were transiently transfected with pcDNA or pcDNA-HBXIP along with pGL-P2 (WT) or those constructs with mutated binding sites of Sp1 (Sp1-M) and E2F1 (E2F1-M). d, e The activity of PKM promoter (d) and the protein level of PKM2 (e) were separately examined by luciferase reporter gene assay and immunoblotting assay in MCF-7 cells. The cells were transiently transfected with indicated plasmids or siRNAs. Statistically significant differences are indicated: **P < 0.01, ***P < 0.001; all experiments were repeated at least three times. NS, not significant