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Analysis of the mechanism of action of the Brazilian type ( A γ −195 C → G) of hereditary persistence of fetal hemoglobin
Author(s) -
Takahashi T.,
Schreiber R.,
Krieger J. E.,
Saad S. T. O.,
Costa F. F.
Publication year - 2003
Publication title -
european journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.904
H-Index - 84
eISSN - 1600-0609
pISSN - 0902-4441
DOI - 10.1046/j.0902-4441.2003.00161.x
Subject(s) - fetal hemoglobin , microbiology and biotechnology , mutant , biology , globin , promoter , locus control region , mutation , gene , gene expression , genetics , fetus , pregnancy
We report an in vitro expression study of the A γ ‐globin gene promoter containing the A γ −195 C → G mutation that causes the Brazilian type of hereditary persistence of fetal hemoglobin (HPFH). To demonstrate that this mutation results in increased promoter strength, we evaluated the mutant promoter linked to the hypersensitive site‐2 of the locus control region with the luciferase reporter gene system and examined protein interactions by eletrophoretic mobility shift assay. The transient expression was studied in three cell lines: K562, HEL and 293, and indicated increased promoter activity of the promoter containing the Brazilian mutation in all cell lines. The protein–DNA interaction showed that, in contrast to the A γ −198 T → C mutation which has increased affinity for the Sp1 protein and creates a motif that behaves like a novel CACCC box in the γ promoter, the Brazilian HPFH mutation decreases the affinity at the Sp1 protein and does not act as a CACCC motif. These results suggest that this mutation may act to increase the A γ ‐globin chain production. In addition, the mechanism by which this increased production occurs is different to that of the −198 mutation. Other proteins may be involved in the overexpression of the γ ‐globin chain and/or may be dependent upon the DNA structure.