title: Expression of the histo-blood group B gene predominates in AB-genotype cells.
abstract: BACKGROUND
  It has been demonstrated that the 43-bp minisatellite sequence in the 5' region of the ABO gene plays an important role in its transcriptional regulation. It was determined in previous investigations that the structure of the minisatellite enhancer was specific to A, B, and O alleles.
  
  
  METHODS
  Real-time polymerase chain reaction (PCR) detection and a PCR-restriction fragment length polymorphism (RFLP) strategy were used to compare the quantities of the A and B transcripts in AB-genotype cells, including peripheral blood cells and cancer cell line with the group AB phenotype. The 5' 3.7-kb regions of the A and B genes were cloned and the sequences compared. The transcriptional activities of the 5' segments of the A and B genes were compared with luciferase reporter assay.
  
  
  RESULTS
  Both real-time PCR and PCR-RFLP analyses show that there is evidently more of the B transcript in the AB-genotype cells. It was demonstrated that the 5' segment of the B gene had a markedly higher transcription-activation activity relative to the A gene. This difference in transcription capability appears to result from the variation in minisatellite-enhancer structures in the A and B genes, which contain one and four repeats of the 43-bp enhancer unit, respectively.
  
  
  CONCLUSIONS
  Our study indicates that the majority of steady-state mRNA within AB-genotype cells is composed of the B transcript and that this phenomenon is due to the predominant expression of the B gene relative to the A gene.
authors.affiliation: Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan.
authors.forename: Yuh-Ching
authors.initials: YC
authors.lastname: Twu
authors.forename: Chuang-Yi
authors.initials: CY
authors.lastname: Hsieh
authors.forename: Lung-Chih
authors.initials: LC
authors.lastname: Yu
mesh_terms: D000017:ABO Blood-Group System / Q000096:biosynthesis / Q000235:genetics*; D000483:Alleles; D045744:Cell Line, Tumor; D004742:Enhancer Elements, Genetic / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology*; D005838:Genotype; D006801:Humans; D018598:Minisatellite Repeats / Q000235:genetics; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length; D014158:Transcription, Genetic
chemical_list: D000017:ABO Blood-Group System