Expression of Human Histo-blood Group ABO Genes Is Dependent upon DNA Methylation of the Promoter Region

Abstract

We have investigated the regulatory role of DNA methylation in the expression of the human histo-blood group ABO genes. The ABO gene promoter region contains a CpG island whose methylation status correlates well with gene expression in the cell lines tested. The CpG island was found hypomethylated in some cell lines that expressed ABO genes, whereas the other cell lines that did not express ABO genes were hypermethylated. The ABO blood group system discovered by Karl Landsteiner (1) at the beginning of this century is of great importance in blood transfusions and organ transplantations. Two carbohydrate antigens, A-and B-antigens, and their antibodies constitute this system. The A and B functional alleles at the ABO genetic locus encode glycosyltransferases ␣133GalNAc transferase (designated A-transferase) and ␣133Gal transferase (designated B-transferase), respectively. A-transferase transfers a GalNAc residue from UDP-GalNAc to the precursor H substrate, producing A antigens as defined by the trisaccharide determinant structure, GalNAc␣133(Fuc␣132)Gal␤13 R. Similarly, B-transferase catalyzes the transfer of a Gal from UDP-Gal to the same H substrate, producing B antigens defined by Gal␣133(Fuc␣132)Gal␤13 R (2-5). Molecular genetic studies of the human ABO genes have identified two critical single base substitutions that result in amino acid substitutions responsible for the different donor nucleotidesugar substrate specificity between A-and B-transferases. A single base deletion, which shifts the reading frame of codons and abolishes the function of A-transferase, has been identified in most O alleles (6, 7).The ABO genes are expressed in a cell type-specific manner; the isoantigens A, B, and H of blood groups A, B, and O are not confined to red cells only but are also found in most secretions and on some epithelial cells. However, they are absent in connective tissues and the central nervous system (8). ABH antigens are known to undergo drastic changes during development, differentiation, and maturation of normal cells (9). In addition to these physiological processes, profound changes have also been documented in pathological processes such as tumorigenesis. Reduction or complete deletion of A/B antigen expression in bladder and oral cancers has been documented, as well as the apparent onco-developmental expression of the ABH antigens in gastric and distal colon tumors (10 -12). Moreover, the loss of ABH antigens has been correlated with tumor progression of various carcinomas including lung and bladder carcinomas (13-16). Thus, delineation of regulatory mechanism is essential to understand these complicated expression patterns of the ABO genes.In an initial attempt to elucidate the molecular mechanism controlling the expression of the human ABO genes, we isolated several genomic clones that covered the ABO genes over 18 kb 1 (17). A 4.7-kb EcoRI/NcoI 5Ј-upstream fragment flanking the coding sequence in exon 1 of the human ABO gene was subcloned into the promoterless pGL3-basic vector upstream of the lucifer...

Loss of blood group A antigen expression in bladder cancer caused by allelic loss and/or methylation of the ABO gene

“…Reportedly, the promoter region of the ABO gene is located between À117 and þ 31 from the translation start site, of which hypermethylation regulates gene expression. 19,20 In the present study, we divided CpG island spanning À789 to þ 6 into six regions and examined the methylation status by BiPS analysis (Figure 2). In the preliminary experiment, methylated DNA could be identified as the extra band, if more than 25% of the template DNA was methylated (data not shown).…”

“…Recent advance in cancer epigenetics shed light on the reduced expression of A antigen in malignant cells. Kominato et al 19,20 reported that hypermethylation of the promoter region of the ABO gene induced ABO gene silencing in their study using a human stomach carcinoma cell line. Iwamoto et al 21 established subclones with positive or negative expression of the A antigen from parental colonic cancer cell lines and reported a distinct difference in the methylation pattern of the CpG island of the promoter region of the ABO glycosyltransferase, that is densely methylated in a subclone lacking the expression of the A antigen.…”

Rat Encodes the Paralogous Gene Equivalent of the Human Histo-blood Group ABO Gene

“…Rat chemical-induced colorectal cancer also changed the ABH antigen expression (13). The ABH gene expression was down-regulated in A-negative human colorectal cancer cells by the methylation of the promoter and the reduced activity of the enhancer element of the gene (31,32). The presented cDNA data should contribute for investigation in alteration of the rat ABO homologue expression in the chemical oncogenesis.…”

Loss of heterozygosity at 9q33 and hypermethylation of the DBCCR1 gene in oral squamous cell carcinoma

“…PCR was carried out using the HotStarTaq Kit (Qiagen); the annealing temperatures for the unmethylated and methylated reactions were 60 and 621C, respectively. Primer sequences and reaction conditions for MS-PCR analysis of the ABO gene promoter were as described (Kominato et al, 1999;Gao et al, 2004). The PCR products were resolved on 2% agarose gels.…”