Genomic structure and transcriptional regulation of human Galbeta1,3GalNAc alpha2,3-sialyltransferase (hST3Gal I) gene.
Previous studies have shown that hST3Gal I mRNA is overexpressed in colorectal cancer tissues and primary breast carcinoma compared with nonmalignant or benign tissue, suggesting that the transcriptional regulation of hST3Gal I gene is altered during malignant transformation. We report transcriptional regulation of the hST3Gal I gene in colon adenocarcinoma and leukemia cell lines. To determine the genomic structure of the 5'-untranslated region, we cloned and identified the 5'-untranslated region of hST3Gal I from a human genome library. The 5'-untranslated region was found to be divided into three exons, namely, exons Y, X, and C1. The transcription initiation sites map at -1035 bp from the translation initiation site. Our results indicate that the transcriptional regulation of hST3Gal I depends on the pI promoter that exists 5'-upstream of exon Y in these cell lines. The results of luciferase assay suggest that the nt -304 to -145 region is important for transcriptional activity of hST3Gal I gene in both cell lines. The nt -304 to -145 region contains two sequences similar to the Sp1 recognition elements (GC-box) and one USF binding site. The results of site-directed mutagenesis indicated that the Sp1 binding sites and USF binding site of the pI promoter are involved in the transcription of hST3Gal I mRNA. However, the triple mutant of these sites still exhibits about 50% transcriptional activity, suggesting that there are other transcription factors involved in the transcription of hST3Gal I mRNA. These results suggest that these factors may play a critical role in the up-regulation of the hST3Gal I gene during malignant transformation.
Taniguchi
A
A
Department of Clinical Chemistry, School of Pharmaceutical Sciences, Toho University, 2-2-1, Miyama, Funabashi, Chiba 274-8510, Japan.
Yoshikawa
I
I
Matsumoto
K
K
D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA; D005091:Exons; D015971:Gene Expression Regulation, Enzymologic; D016678:Genome; D006801:Humans; D008969:Molecular Sequence Data; D012799:Sialyltransferases / Q000235:genetics*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D000094663:beta-Galactoside alpha-2,3-Sialyltransferase
D004247:DNA; D012799:Sialyltransferases; D000094663:beta-Galactoside alpha-2,3-Sialyltransferase; C000722087:ST3GAL1 protein, human