Fig. 4

Sp1 binds the -123 bp region of the FST promoter to regulate its activity. Expression of constitutively active Sp1 in cav-1 WT MC increased activity of both the Sp1 reporter construct (a) (n = 3, *p < 0.05) and mFST-123-luc (b) (n = 6, *p < 0.05). c Effective siRNA-mediated Sp1 knockdown in cav-1 WT and KO MC was confirmed by immunoblotting. d Sp1 knockdown abolished the increased transcriptional activity of the -123 bp FST promoter in cav-1 KO MC, with little effect in WT cells (n = 6, *vs WT con siRNA, #vs KO con siRNA, p < 0.05). e Sp1 knockdown repressed the elevation in FST mRNA expression in cav-1 KO MC (n = 3, *vs WT con siRNA, #vs KO con siRNA, p < 0.05). f Similar effects of Sp1 knockdown on FST protein expression were seen (n = 4, *vs WT con siRNA, #vs KO con siRNA, p < 0.05). g Sp1 binding within the -123 bp region of the FST promoter at the predicted Sp1 binding sites was significantly elevated in cav-1 KO MC as assessed by ChIP (n = 14, p < 0.05). h Graphical representation of the deletion of the two predicted Sp1 binding sites within the -123 bp promoter region of FST (mFST4–123ΔSp1-luc). i Deletion of the two Sp1 binding sites attenuated transcriptional activity of mFST4–123-luc in cav-1 WT and normalized activity in cav-1 KO MC to levels seen in WT cells (n = 9, *vs WT mFST-123-luc, #vs KO mFST-123-luc, p < 0.05)