GATA-1 transcription is controlled by distinct regulatory mechanisms during primitive and definitive erythropoiesis

Abstract

Transcription factor GATA-1 is required for the terminal differentiation of both the primitive and definitive erythroid cell lineages, and yet the regulatory mechanisms of GATA-1 itself are not well understood. To clarify how the GATA-1 gene is transcriptionally controlled in vivo, presumptive regulatory regions of the gene were tested by fusion to a reporter gene and then examined in transgenic mice. We found that a transcriptional control element located between ؊3.9 and ؊2.6 kb 5 to the erythroid first exon serves as an activating element and that this sequence alone is sufficient to recapitulate the expression of GATA-1 (but uniquely in primitive erythroid cells). Addition of sequences from the GATA-1 first intron to this upstream element provides a necessary and sufficient condition for complete recapitulation of GATA-1 expression in both primitive and definitive erythroid cells. The first intron element does not possess intrinsic transcriptional activation potential when linked to the GATA-1 gene promoter but rather requires the upstream activating element for its activity. These experiments show that GATA-1 gene expression is regulated by discrete transcriptional control elements during definitive and primitive erythropoiesis: The 5 element displays properties anticipated for a primitive erythroid cell-specific activating element, and the novel element within the GATA-1 first intron specifically augments this activity in definitive erythroid cells.

Increased dosage of Runx1/AML1 acts as a positive modulator of myeloid leukemogenesis in BXH2 mice

“…To test the hypothesis that an increased dose of RUNX1 is responsible for the hematopoietic abnormalities, we generated Tg mice that express mouse Runx1 under the control of the hematopoietic regulatory domain (HRD) of GATA-1 (Runx1 Tg) (Onodera et al, 1997). We used the GATA-1 HRD promoter because GATA-1 is a key transcription factor in the differentiation of both erythrocytes and megakaryocytes (Shivdasani et al, 1997), which are two sublineages in a fraction of myeloid lineage cells, and mutations in this gene are associated with DS-AMKL, one of the intriguing case where an increased dose of RUNX1 is possibly implicated in leukemogenesis (Wechsler et al, 2002;Gurbuxani et al, 2004).…”

Deletion of a Negatively Acting Sequence in a Chimeric GATA-1 Enhancer-Long Terminal Repeat Greatly Increases Retrovirally Mediated Erythroid Expression

“…DNA Sequences Regulating GATA-1 Expression-The DNA region surrounding the HS1 site of the mouse GATA-1 gene appears to play a central role in GATA-1 expression in transgenic experiments, as it is essential for high level activity in hematopoietic cells in general, and in particular for expression in embryonic erythroblasts (12)(13)(14)(15)(16). It is likely that a certain degree of functional redundancy exists in the GATA-1 gene region; in fact, the deletion from the endogenous GATA-1 gene of a region comprising HS1, by homologous recombination, has little effect on GATA-1 expression in erythroid cells (7).…”

“…Constructs including the mouse GATA-1 promoter up to a DNase I-hypersensitive site lying at about Ϫ700 nts 1 (HS2) are expressed, at low efficiency, in adult hematopoietic cells in transgenic mice but not in yolk sac cells; however, constructs including an additional more upstream site (HS1) are much more efficient and are also active in primitive hematopoietic cells (12)(13)(14)(15)(16). GATAbinding sequences in HS1 and HS2 are essential for activity in a variety of constructs, suggesting GATA-1 auto-regulation (8 -10, 14 -16); however, a GATA-1 transgenic construct is active in mice lacking the endogenous GATA-1 gene, suggesting that other members of the GATA family of transcription factors (possibly GATA-2) may control GATA-1 transcription (13,16).…”

“…The regulation of the expression of GATA-1 itself has been the subject of many investigations (7)(8)(9)(10)(11)(12)(13)(14)(15)(16). Constructs including the mouse GATA-1 promoter up to a DNase I-hypersensitive site lying at about Ϫ700 nts 1 (HS2) are expressed, at low efficiency, in adult hematopoietic cells in transgenic mice but not in yolk sac cells; however, constructs including an additional more upstream site (HS1) are much more efficient and are also active in primitive hematopoietic cells (12)(13)(14)(15)(16).…”

Mast cell transcriptional networks

“…However, a number of regions critical for GATA-1 expression in erythroid cells and megakaryocytes have been identified by transgenic reporter experiments and targeted deletions in mice, and are summarized in figure 3. A genomic region that includes DNase 1 hypersensitive site lies approximately 3.5 kilobases upstream of the IE exon and can direct expression in primitive and definitive erythroid precursors and megakaryocytes, and has been referred to as an upstream enhancer (69)(70)(71). The large GATA-1 first intron contains exon IB and is important for definitive hematopoiesis, particularly in specifying expression in erythroid cells and megakaryocytes (72;73).…”