Identification of a novel erythroid-specific enhancer for the ALAS2 gene and its loss-of-function mutation which is associated with congenital sideroblastic anemia.
نویسندگان
چکیده
Erythroid-specific 5-aminolevulinate synthase (ALAS2) is the rate-limiting enzyme for heme biosynthesis in erythroid cells, and a missense mutation of the ALAS2 gene is associated with congenital sideroblastic anemia. However, the gene responsible for this form of anemia remains unclear in about 40% of patients. Here, we identify a novel erythroid-specific enhancer of 130 base pairs in the first intron of the ALAS2 gene. The newly identified enhancer contains a cis-acting element that is bound by the erythroid-specific transcription factor GATA1, as confirmed by chromatin immunoprecipitation analysis in vivo and by electrophoretic mobility shift assay in vitro. A promoter activity assay in K562 human erythroleukemia cells revealed that the presence of this 130-base pair region increased the promoter activity of the ALAS2 gene by 10-15-fold. Importantly, two mutations, each of which disrupts the GATA-binding site in the enhancer, were identified in unrelated male patients with congenital sideroblastic anemia, and the lower expression level of ALAS2 mRNA in bone marrow erythroblasts was confirmed in one of these patients. Moreover, GATA1 failed to bind to each mutant sequence at the GATA-binding site, and each mutation abolished the enhancer function on ALAS2 promoter activity in K562 cells. Thus, a mutation at the GATA-binding site in this enhancer may cause congenital sideroblastic anemia. These results suggest that the newly identified intronic enhancer is essential for the expression of the ALAS2 gene in erythroid cells. We propose that the 130-base pair enhancer region located in the first intron of the ALAS2 gene should be examined in patients with congenital sideroblastic anemia in whom the gene responsible is unknown.
منابع مشابه
Identification of the novel erythroid-specific enhancer for ALAS2 gene and its loss-of-function mutation associated with congenital sideroblastic anemia
متن کامل
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متن کاملRED CELLS A promoter mutation in the erythroid-specific 5-aminolevulinate synthase (ALAS2) gene causes X-linked sideroblastic anemia
X-linked sideroblastic anemia (XLSA) is caused by mutations in the erythroidspecific 5-aminolevulinate synthase gene (ALAS2). XLSA was diagnosed in a 32year-old woman with a mild phenotype and moderately late onset. Pyridoxine therapy had no effect in the proband, but in her affected son engendered a modest increase in hemoglobin concentration and a 4-fold reduction in ferritin iron. Molecular ...
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عنوان ژورنال:
- Haematologica
دوره 99 2 شماره
صفحات -
تاریخ انتشار 2014