Involvement of NF-kappaB in the regulation of S100A6 gene expression in human hepatoblastoma cell line HepG2.
S100A6 (calcyclin) is an acidic calcium binding protein with two EF-hand motifs and overexpressed in several tumors including intrahepatic carcinoma. TNFalpha, a strong NF-kappaB activator required for hepatocyte proliferation during liver regeneration, triggered the expression of S100A6 mRNA in human hepatoblastoma cell line HepG2. Transient expression of NF-kappaB (p65) increased S100A6 promoter activity and expression of inhibitor of NF-kappaB (IkappaBalpha) decreased TNFalpha-induced S100A6 promoter activity. To confirm the involvement of NF-kappaB in S100A6 promoter activation, we analyzed serially deleted promoter constructs of the S100A6 gene by luciferase reporter assay and found a NF-kappaB-responsive DNA fragment at the position between -584 and -361. Electrophoretic mobility shift assays showed that TNFalpha induced p65 binding to a potential NF-kappaB binding site at -460/-451. Furthermore, treatment of cells with CAPE (caffeic acid phenethyl ester), a specific NF-kappaB (p65) inhibitor, decreased NF-kappaB binding and promoter activity. These results suggest that NF-kappaB transcription factor contributes to the activation of S100A6 gene expression in response to TNFalpha in HepG2 cells.
Joo
Joung Hyuck
JH
Cell Biology Laboratory, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon, Republic of Korea.
Kim
Jae Wha
JW
Lee
Younghee
Y
Yoon
Sun Young
SY
Kim
Joo Heon
JH
Paik
Sang-Gi
SG
Choe
In Seong
IS
D001665:Binding Sites; D018797:Cell Cycle Proteins; D015972:Gene Expression Regulation, Neoplastic; D018197:Hepatoblastoma / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D018797:Cell Cycle Proteins; D016328:NF-kappa B; D012333:RNA, Messenger; D000075383:S100 Calcium Binding Protein A6; D009418:S100 Proteins; D014409:Tumor Necrosis Factor-alpha; C055351:S100A6 protein, human