Comparative analysis of the genomic structures and promoter activities of mouse Siaalpha2,3Galbeta1,3GalNAc GalNAcalpha2, 6-sialyltransferase genes (ST6GalNAc III and IV): characterization of their Sp1 binding sites

Abstract

The genomic organization of the genes encoding the mouse N-acetylgalactosamine alpha2,6-sialyltransferase specific for Siaalpha2,3Galbeta1,3GalNAc (ST6GalNAc III and IV) has been determined. The ST6GalNAc III gene spans over 120 kilobases of genomic DNA with 5 exons; on the other hand, the ST6GalNAc IV gene spans over 12 kilobases of genomic DNA with 6 exons. But the exon-intron boundaries of these genes are very similar. The 5'-flanking regions of these genes do not contain a TATA- or CAAT-box but have three putative Sp1 binding sites for each promoter. Transient transfection experiments demonstrated functional promoter activity in an ST6GalNAc III-expressing cell line, P19, for the ST6GalNAc III promoter, and in an ST6GalNAc IV-expressing cell line, NIH3T3, for the ST6GalNAc IV promoter. Mobility shift assaying and mutational analysis of the promoter region indicated that two of the three Sp1 binding sites are involved in the transcriptional regulation of the ST6GalNAc III gene in P19 cells, while all three Sp1 binding sites are involved in the transcriptional regulation of the ST6GalNAc IV gene in NIH3T3 cells.