Silencing of ^Aγ-Globin Gene Expression during Adult Definitive Erythropoiesis Mediated by GATA-1-FOG-1-Mi2 Complex Binding at the −566 GATA Site

Abstract

Autonomous silencing of ␥-globin transcription is an important developmental regulatory mechanism controlling globin gene switching. An adult stage-specific silencer of the A ␥-globin gene was identified between ؊730 and ؊378 relative to the mRNA start site. A marked copy of the A ␥-globin gene inserted between locus control region 5 DNase I-hypersensitive site 1 and the -globin gene was transcriptionally silenced in adult ␤-globin locus yeast artificial chromosome (␤-YAC) transgenic mice, but deletion of the 352-bp region restored expression. This fragment reduced reporter gene expression in K562 cells, and GATA-1 was shown to bind within this sequence at the ؊566 GATA site. Further, the Mi2 protein, a component of the NuRD complex, was observed in erythroid cells with low ␥-globin levels, whereas only a weak signal was detected when ␥-globin was expressed. Chromatin immunoprecipitation of fetal liver tissue from ␤-YAC transgenic mice demonstrated that GATA-1, FOG-1, and Mi2 were recruited to the A ␥-globin ؊566 or G ␥-globin ؊567 GATA site when ␥-globin expression was low (day 18) but not when ␥-globin was expressed (day 12). These data suggest that during definitive erythropoiesis, ␥-globin gene expression is silenced, in part, by binding a protein complex containing GATA-1, FOG-1, and Mi2 at the ؊566/؊567 GATA sites of the proximal ␥-globin promoters.

Original Research: Stable expression of miR-34a mediates fetal hemoglobin induction in K562 cells

“…[4][5][6][7][8][9][10][11] Although under tight transcriptional control, the g-globin genes are also modulated by translational events. For example, sickle cell patients treated with butyrate had rapid increases in HbF levels in reticulocytes supporting g-globin regulation independent of transcriptional activation 12 implicating translational mechanisms of control.…”

Mta3-NuRD complex is a master regulator for initiation of primitive hematopoiesis in vertebrate embryos

“…Previous studies have shown that NuRD complexes play critical roles within specific subsets of hematopoietic cells, for example, in megakaryocyte differentiation, 15,16 T-and B-lymphocyte development, [17][18][19][20] erythroid differentiation, [21][22][23][24] and adult bone marrow hematopoiesis. 25 However, it is not known whether NuRD complexes are involved in primitive hematopoiesis.…”

Fetal hemoglobin chemical inducers for treatment of hemoglobinopathies

“…A recent study has provided evidence that the silencing function of this promoter region is exerted by the binding of a protein complex containing GATA-1, FOG-1, and Mi2 at the −566/−567 GATA site [74].…”