Levels of Hb A2 in heterozygotes and homozygotes for beta-thalassemia mutations: influence of mutations in the CACCC and ATAAA motifs of the beta-globin gene promoter.

摘要: The author summarizes the Hb A2 levels in over 600 β-thalassemia heterozygotes with 32 different base changes or frameshifts and 22 for 1 of 5 large deletions. Three major groups are recognized: persons β°-thalassemia β+-thalassemia (severe) have between 4.5 5.5%, those mild alleles 3.6 4.2%, still lower values silent mutations. High were observed subjects 2 β+ mutations β-globin gene promoter (-88, C→T -29, A→G); unusually high also present several -88 -29 homozygotes. Data members 8 families which (C→T) the-29 (A→G) mutation, -1,393-bp deletion, is cis trans to a δ-globin mutation support earlier observations that an increase δ-chain synthesis occurs either one these 3 alleles. A review data confirms suggestion results from at least two mechanisms: posttranslational system, formation αδ-dimers promoted when excess α-chains available, while certain transcription because change binding factors.