Bile acids activate epidermal growth factor receptor via a transforming growth factor-alpha-dependent mechanism

Abstract

tional activity by deacetylation, and that antisense INGlb strongly up-regulated alpha[;etoprotein (AFP) gene expression. Based upon these observations, we investigated the mechainsm by which p53, hS1R2 and ING affect expression of the AFP gene. (Methods) 1. ING tamily members (INGla, ]b, lc, 2, 3), p53 and hS1R2 were transfected into HepG2 cells which contain a wild type p53 gene, along with the AFP reporter vector and dualluciierase assays were performed. As a control, p21 promoter regulation which is known to be stimulated by p53 was also examined Luciferase assays using various lengths of truncated AFP promoter were also done 2 lmmunoprecipitation of ING1 and hSIR2 was peflormed and the effect of 1NGI on hSIR2 activity was analyzed. 3, Gel shift and supershift assays nsing the AT-motif found in the AFP promoter region was performed. 4, The effect of histuue deacetylase 1 (HDAC1) was investigated by over expression and addition of the HDAC inhibitor, trichnstatin A (TSA). (Results) 1, INGlb, INGlc, ING2 and p53 repressed the AFP promoter and by contrast, they activated the p21 promoter, INGla repressed both genes and ING3 did not repress AFE hS1R2 increased AFP and repressed p21 through inhibiting p53 2 ING1 bound to hSIR2 by protein-protein interaction and 1NG1 activated p53 wa inhibiting hS1R2 3 INGI also bound to AT-motif in AFP promoter. 4. HDAC1 rapressed both genes trans<ription and the elti~ct of INGlb, ING2 and p53 was inhibited by TSA (Condnsions) lNG family members showed different effects on transcriptional regulation, ING1 represses AFP transcription by activating p53 through binding and inhibiting hS1R2 deacetylation ettects. ING1 also directly binds to a region of the AFP promoter and represses it ~a an HDACl-linked mechanism, The decreased expression of 1NG1 might be important tbr AFP production in hepatocellular cancer cells.