Alternative promoter identified between a hypermethylated upstream region of repetitive elements and a CpG island in human ABO histo-blood group genes.

We have studied the expression of human histo-blood group ABO genes during erythroid differentiation, using an ex vivo culture of AC133(-)CD34(+) cells obtained from peripheral blood. 5'-Rapid amplification of cDNA ends analysis of RNA from those cells revealed a novel transcription start site, which appeared to mark an alternative starting exon (1a) comprising 27 bp at the 5'-end of a CpG island in ABO genes. Results from reverse transcription-PCR specific to exon 1a indicated that the cells of both erythroid and epithelial lineages utilize this exon as the transcription starting exon.

Expression of ABO or related antigenic carbohydrates on viral envelopes leads to neutralization in the presence of serum containing specific natural antibodies and complement.

No definitive biologic function has been associated with the human ABO histo-blood group polymorphism, or any other terminal carbohydrate differences within or between closely related species. We have experimentally addressed the question of whether viral particles can become glycosylated as determined by the glycosylation (eg, ABO) status of the producer cell and as a result be affected by human serum containing specific natural antibodies (NAbs). Measles virus was produced in cells transfected with cDNA encoding, either human A-transferase, B-transferase, an inactive "O-transferase," or a pig alpha1-3galactosyltransferase (alpha1-3GT) synthesizing the Galalpha1-3Gal structure.