title: Deletion of the RUNX1 binding site in the erythroid cell-specific regulatory element of the ABO gene in two individuals with the Am phenotype.
abstract: OBJECTIVE
  An erythroid cell-specific regulatory element, referred to as the +5·8-kb site, had been identified in the first intron of the human ABO blood group gene. Subsequent studies revealed that either a 5·8-kb deletion including the +5·8-kb site or disruption of a GATA factor binding motif at the site was present in all Bm and ABm individuals examined. We investigated the molecular mechanism of the Am phenotype, which is analogous to the Bm phenotype.
  
  
  METHODS
  Genomic DNAs were prepared from peripheral blood of two Am individuals, and the nucleotide sequences were investigated using PCR and direct sequencing. Electrophoretic mobility shift assay (EMSA) and promoter assay with K562 cells were carried out.
  
  
  RESULTS
  A novel 23-bp nucleotide deletion was found at the +5·8-kb site in both individuals. EMSAs demonstrated binding of the transcription factor RUNX1 to the nucleotides within the deletion. Promoter assays showed that the deletion reduced the transcriptional activity of the +5·8-kb site.
  
  
  CONCLUSIONS
  Deletion of the 23-bp nucleotides including the RUNX1 binding site decreases transcription of the A allele, resulting in the reduction in A antigen expression in the Am phenotype.
authors.affiliation: Department of Legal Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Isa
authors.forename: R
authors.initials: R
authors.lastname: Sano
authors.forename: T
authors.initials: T
authors.lastname: Nakajima
authors.forename: R
authors.initials: R
authors.lastname: Kubo
authors.forename: K
authors.initials: K
authors.lastname: Takahashi
authors.forename: Y
authors.initials: Y
authors.lastname: Kominato
authors.forename: H
authors.initials: H
authors.lastname: Tsuneyama
authors.forename: K
authors.initials: K
authors.lastname: Ogasawara
authors.forename: M
authors.initials: M
authors.lastname: Uchikawa
mesh_terms: D000017:ABO Blood-Group System / Q000235:genetics*; D000483:Alleles; D001483:Base Sequence; D001665:Binding Sites; D050676:Core Binding Factor Alpha 2 Subunit / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D006801:Humans; D007438:Introns; D020014:K562 Cells; D008969:Molecular Sequence Data; D010641:Phenotype; D011401:Promoter Regions, Genetic; D050436:Regulatory Elements, Transcriptional; D017384:Sequence Deletion; D014158:Transcription, Genetic
chemical_list: D000017:ABO Blood-Group System; D050676:Core Binding Factor Alpha 2 Subunit; C493728:RUNX1 protein, human
keywords: A m; ABO blood group; RUNX1; enhancer; transcription