The distinctive roles of erythroid specific activator GATA-1 and NF-E2 in transcription of the human fetal γ-globin genes

Abstract

GATA-1 and NF-E2 are erythroid specific activators that bind to the β-globin locus. To explore the roles of these activators in transcription of the human fetal stage specific γ-globin genes, we reduced GATA-1 and p45/NF-E2 using shRNA in erythroid K562 cells. GATA-1 or p45/NF-E2 knockdown inhibited the transcription of the γ-globin genes, hypersensitive site (HS) formation in the LCR and chromatin loop formation of the β-globin locus, but histone acetylation across the locus was decreased only in the case of GATA-1 knockdown. In p45/NF-E2 knockdown cells, GATA-1 binding was maintained at the LCR HSs and γ-globin promoter, but NF-E2 binding at the LCR HSs was reduced by GATA-1 knockdown regardless of the amount of p45/NF-E2 in K562 cells. These results indicate that histone acetylation is dependent on GATA-1 binding, but the binding of GATA-1 is not sufficient for the γ-globin transcription, HS formation and chromatin loop formation and NF-E2 is required. This idea is supported by the distinctive binding pattern of CBP and Brg1 in the β-globin locus. Furthermore GATA-1-dependent loop formation between HS5 and 3′HS1 suggests correlation between histone modifications and chromatin looping.

The hematopoietic regulator TAL1 is required for chromatin looping between the β-globin LCR and human γ-globin genes to activate transcription

“…Together, these results show that TAL1 does not have a role in HSs formation and histone modifications, including H3K9/14ac, H3K27ac and H3K4me2 in the β-globin locus in K562 cells. These chromatin modifications appear to depend on GATA-1 and NF-E2 (6).

Figure 3.MNase sensitivity and histone modifications of the β-globin locus in TAL1 knockdown K562 cells.

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“…Histones are acetylated in the β-globin locus when NF-E2 expression is reduced in K562 cells, even though HSs and a chromatin loop are not formed normally (6). HSs in the β-globin locus are formed without the loop formation as shown in this study where TAL1 was reduced.…”

The transcription factor, Nuclear factor, erythroid 2 (Nfe2), is a regulator of the oxidative stress response during Danio rerio development

“…Hematopoiesis is well conserved across vertebrates (Galloway and Zon, 2003), and Nfe2 has been implicated as a critical regulator of globin gene expression (Blank et al, 1997; Kotkow and Orkin, 1995; Lu et al, 1994; Woon Kim et al, 2011). Both the mouse model (Shivdasani and Orkin, 1995) and our KO early larval zebrafish have hypochromia (Suppl Fig.…”

Homozygosity for a haplotype in the HBG2‐OR51B4 region is exclusive to Arab‐Indian haplotype sickle cell anemia

“…DNA sequence motifs that are most conserved include GATA sequences in HS-2, HS-3 and HS-4, KLF1 binding sites in HS-2 and HS-3, and an E-box motif in HS-2 [27]. GATA1 is required for chromatin loop formation between hypersensitive sites and gene promoters [28]. LCR looping to globin gene promoters is facilitated by the LDB1/LMO2/GATA-1/TAL-1 erythroid specific protein complex (Lbd1 complex) [29-31].…”

“…TAL1 overexpression increases its occupancy at HS-4 and HS-2 enhancing the expression of HBG. GATA1 and NF-E2 are both required for chromatin loop formation between the LCR and the active γ-globin genes in K562 cells [28]. RNA sequencing revealed a transcript from this region in human CD34 + cells and non-coding RNAs might play a role in modifying histones across the LCR and looping with HBG2 promoter [32].…”