Valproic acid-mediated transcriptional regulation of human GM3 synthase （hST3Gal V） in SK-N-BE（2）-C human neuroblastoma cells

Aim： To investigate whether valproic acid （VPA） modulates human GM3 synthase （hST3Gal V） mRNA expression, as a part of ganglioside GM3 biosynthesis, in human neuroblastoma cells. Methods： Using RT-PCR and immunofluorescent confocal microscopy, we examined hST3Gal V mRNA and GM3 levels during VPA-induced differentiation of human neuroblastoma SK-N-BE（2）-C cells. We characterized the VPA-inducible promoter region within the hST3- Gal V gene using luciferase constructs carrying 5′-deletions of the hST3Gal V promoter. Results： RT-PCR indicated that VPA-mediated hST3Gal V induction is transcriptionally regulated. Functional analysis of the 5′-flanking region of the hST3Gal V gene demonstrated that the -177 to -83 region, which contains a cAMP-responsive element （CRE） at -143, functions as the VPA-inducible promoter by actively binding CRE binding protein （CREB）. In addition, sitedirected mutagenesis and electrophoretic mobility shift assay indicated that the CRE at -143 is crucial for the VPA-induced expression of hST3Gal V in SK-N- BE（2）-C cells. Conclusion： Our results isolated the core promoter region in the hST3Gal V promoter, a CRE at -143, and demonstrated that it is essential for transcriptional activation of hST3Gal V in VPA-induced SK-N-BE（2）-C cells. Subsequent CREB binding to this CRE mediates VPA-dependent upregulation of hST3Gal V gene expression.