Characterization of the promoter region of the human Galbeta1,3(4)GlcNAc alpha2,3-sialyltransferase III (hST3Gal III) gene.

Multiple promoters are found in the hST3Gal IV, hST3Gal V and hST3Gal VI genes. These promoters may respond to different physiological signals and stimuli in different cell types. The multiple regulatory pathways of these ubiquitous sialyltransferases may need to be differentially modulated in various cell types. Here, we report transcriptional regulation of the hST3Gal III gene. 5'-RACE analysis determined that the transcription initiation sites map at -181 bp from the translation initiation site in all four cell lines (K-562, HT-29, PC-3 and HepG2) tested. Our results suggest that the hST3Gal III gene does not have multiple mRNAs, as have been identified for the hST3Gal IV, hST3Gal V and hST3Gal VI genes. The 5'-untranslated region was found to be divided into two exons, E1 and E2, indicating that the transcriptional regulation of hST3Gal III depends on the pIII promoter that exists 5'-upstream of exon E1. Luciferase assay results suggest that the nt -303 to -1 region is important for transcriptional activity of the hST3Gal III gene in all four cell lines tested. These results suggest that ubiquitous factors, such as Sp1, may be important for hST3Gal III gene expression.