Valproic Acid Induces Transcriptional Activation of Human GD3 Synthase (hST8SiaⅠ) in SK-N-BE(2)-C Human Neuroblastoma Cells

In this study, we have shown the transcriptional regulation of the human GD3 synthase (hST8SiaⅠ) induced by valproic acid (VPA) in human neuroblastoma SK-N-BE(2)-C cells. To elucidate the mechanism underlying the regulation of hST8Sia Ⅰ gene expression in VPA-stimulated SK-N-BE(2)-C cells, we characterized the promoter region of the hST8Sia Ⅰ gene. Functional analysis of the 5'-flanking region of the hST8Sia Ⅰ gene by the transient expression method showed that the -1146 to -646 region, which contains putative binding sites for transcription factors c-Ets-1, CREB, AP-1 and NF-κB, functions as the VPA-inducible promoter of hST8Sia Ⅰ in SK-N-BE(2)-C cells. Site-directed mutagenesis and electrophoretic mobility shift assay indicated that the NF-κB binding site at -731 to -722 was crucial for the VPA-induced expression of hST8Sia Ⅰ in SK-N-BE(2)-C cells. In addition, the transcriptional activity of hST8Sia Ⅰ induced by VPA in SK-N-BE(2)-C cells was strongly inhibited by SP600125, which is a c-Jun k-terminal kinase (JNK) inhibitor, and GO6976, which is a protein kinase C (PKC) inhibitor, as determined by RT-PCR (reverse transcription-polymerase chain reaction) and luciferase assays. These results suggest that VPA markedly modulated transcriptional regulation of hST8Sia Ⅰ gene expression through PKC/JNK signal pathways in SK-N-BE(2)-C cells.