Analysis of cooperative expression of the genes encoding glycosyltransferases involved in the histo-blood group ABH antigens.

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Synthesis of the histo-blood group ABH antigens requires several glycosyltransferases. The A/B antigens are terminal carbohydrates synthesized by the sequential addition of sugers catalyzed by specific glycosyltransferases. These transferases require α(1,2) fucose modification of the precursor oligonucleotides, and thus A and B antigens can only be synthesized from H antigen. The molecular basis of control of the glycosyltransferase genes is of importance in obtaining a deeper understanding of the regulation and tissue specific expression of the products of those genes.In this study, we demonstrated the expression of antisense transcripts, complementary to the genomic DNA coding strand for the ABO gene encoding ABO glycosyltransferase. Naturally occurring antisense transcriptions have been reported to regulate gene expression through a variety of biological mechanisms. Therefore, the antisense transcript might be involved in the regulation of the ABO gene expression. Further studies will be needed to investigate the presence of antisense RNA to the FUT1 and FUT2 genes encoding α(1,2) fucosytransferase as well as the ABO gene.Moreover, we have confirmed that the ABO gene expression is negatively regulated by N-box upstream of the promoter and that the N box binds with a nuclear factor termed RACP. N-box is recognized by members of bHLH factor. The bHLH family of transcriptional regulators plays crucial roles in the development of various organs and cell types. Previously, we demonstrated that the ABO gene was co-expressed with the FUT1 and FUT2 genes. Inspection of the nucleotide sequences of the upstream region of the FUT1 and FUT2 genes revealed putative binding site of bHLH proteins, suggesting that the bHLH factors could play crucial roles in expression of the genes. Therefore, the N-box binding protein including to the RACP might mediate regulation for cooperative expression of those genes encoding glycosyltransferases involved in the ABH antigens.