Regulatory mechanism for the human glioblastoma cell-specific expression of the human GD1c/GT1a/GQ1b synthase (hST8Sia V) gene.

In this study we observed that human GD1c/GT1a/GQ1b synthase (hST8Sia V) is particularly expressed in human glioblastoma cells. To address the mechanism regulating human glioblastoma-specific gene expression of the hST8Sia V, after the transcription start site (TSS) was identified by the 5'-rapid amplification of cDNA end with total RNA from human glioblastoma U87MG cells, the 5'-flanking region (2.5 kb) of the hST8Sia V gene was isolated and its promoter activity was examined. By luciferase reporter assay, this 5'-flanking region revealed strong promoter activity in only U-87MG cells, but not in other tissue-derived cancer cells. 5'-deletion mutant analysis showed that the region from -1140 to -494 is crucial for transcription of the hST8Sia V gene in U87MG cells. This region contains the activator protein-1 (AP-1) binding site, the main target of the c-Jun N-terminal kinase (JNK) downstream. The AP-1 binding site at -1043/-1037 was proved to be indispensable for the hST8Sia V gene-specific expression in U87MG cells by site-directed mutagenesis. Moreover, the transcriptional activation of hST8Sia V gene in U87MG cells was strongly inhibited by a specific JNK inhibitor, SP600125. These results suggest that the hST8Sia V gene-specific expression in U87MG cells is controlled by JNK/AP-1 signaling pathway.