Fig. 5

Icaritin promotes the suppression of HBP1 on AFP through enhancing HBP1 binding to AFP promoter. a Icaritin promotes the suppression of HBP1 on AFP protein. HepG2 cells were transfected HBP1 with or without Icaritin treatment. The protein levels of HBP1 and AFP were measured by Western blotting. b Icaritin promotes the suppression of HBP1 on AFP mRNA. The mRNA level of AFP was measured by Realtime-PCR in HepG2 cells transfected HBP1 with or without Icaritin treatment. c Icaritin promotes the suppression of HBP1 on AFP promoter. Two hundred-ninety three T cells were co-transfected with AFP promoter and HBP1 with or without Icaritin treatment. Luciferase activity was determined after transfection. d Icaritin promotes the interaction between HBP1 and AFP promoter. Two hundred-ninety three T cells were transfected HA-HBP1 with or without Icaritin treatment. The region from position − 1600 to position − 1448 contains the HBP1 affinity site and was analyzed by specific PCR. e HBP1 protein level is elevated in the presence of Icaritin. HepG2 cells were treated with Icaritin. The protein level of HBP1 was measured by Western blotting (top panel). The mRNA level of HBP1 was measured by Realtime-PCR (bottom panel). f Icaritin inhibits HBP1 ubiquitination-mediated proteasome degradation. HepG2 cells were treated with Icaritin with or without MG132, the protein level of HBP1 was measured by Western blotting (top panel). Two hundred-ninety three T cells were co-transfected HA-HBP1, FLAG-MDM2 with or without Icaritin treatment for 24 h and then exposed to MG132 for another 6 h prior to lysis. HBP1 protein was then isolated by immunoprecipitation and analyzed by anti-Ub antibody (bottom panel). Error bars represent S.D. *, p < 0.05, **, p < 0.01