Sequence analyses and dot-blot analyses with synthetic oligonucleotide probes have identified eight individuals in three Turkish families and one Bulgarian family with one chromosome having a C----T mutation at nucleotide position--101 relative to the Cap site of the beta-globin gene. This nucleotide is part of one of the conserved blocks of nucleotides within the promoter region; in vitro expression analyses with the chloramphenicol acetyltransferase system showed that this substitution will decrease the effectiveness of transcription. Five subjects had a thalassemia intermedia due to the additional presence of a known classical high hemoglobin (Hb) A2 beta-thalassemia mutation on the second chromosome; their hematologic condition was relatively mild. The three persons with a heterozygosity for the--101 C----T mutation had normal hematologic data without microcytosis but with high-normal levels of Hb A2 and a mild imbalance in chain synthesis. The newly discovered mutation is considered one of the silent types of beta- thalassemia. It is relatively rare because it was absent among several hundred normal and beta-thalassemia chromosomes.
A C----T substitution at nt--101 in a conserved DNA sequence of the promotor region of the beta-globin gene is associated with “silent” beta-thalassemia
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JM Gonzalez-Redondo, TA Stoming, A Kutlar, F Kutlar, KD Lanclos, EF Howard, YJ Fei, M Aksoy, C Altay, A Gurgey; A C----T substitution at nt--101 in a conserved DNA sequence of the promotor region of the beta-globin gene is associated with “silent” beta-thalassemia. Blood 1989; 73 (6): 1705–1711. doi: https://doi.org/10.1182/blood.V73.6.1705.bloodjournal7361705
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