Global regulation of erythroid gene expression by transcription factor GATA-1

Abstract

Transcription factor GATA-1 is required for erythropoiesis, yet its full actions are unknown. We performed transcriptome analysis of G1E-ER4 cells, a GATA-1-null erythroblast line that undergoes synchronous erythroid maturation when GATA-1 activity is restored. We interrogated more than 9000 transcripts at 6 time points representing the transition from late burst forming unit-erythroid (BFU-E) to basophilic erythroblast stages. Our findings illuminate several new aspects of GATA-1 function. First, the large number of genes responding quickly to restoration of GATA-1 extends the repertoire of its potential targets. Second, many transcripts were rapidly down-regulated, highlighting the importance of GATA-1 in gene repression. Third, up-regulation of some known GATA-1 targets was delayed, suggesting that auxiliary factors are required. For example, induction of the direct GATA-1 target gene ␤ major globin was late and, surprisingly, required new protein synthesis. In contrast, the gene encoding Fog1, which cooperates with GATA-1 in ␤ globin transcription, was rapidly induced independently of protein synthesis. Guided by bioinformatic analysis, we demonstrated that selected regions of the Fog1 gene exhibit enhancer activity and in vivo occupancy by GATA-1. These findings define a regulatory loop for ␤ globin expression and, more generally, demonstrate how transcriptome analysis can be used to generate testable hypotheses regarding transcriptional networks. ( IntroductionStudies of red blood cell development provide an important basis for understanding general mechanisms of gene regulation and tissue formation. Erythrocyte maturation is largely dedicated to producing hemoglobin and supporting its major function of oxygen delivery. Acquisition of this specialized phenotype is controlled by a concerted differentiation program that serves both generalized and cell type-specific requirements. Production of hemoglobin is coordinated to avoid the toxic accumulation of globins or heme synthetic intermediates. Special adaptations are required for iron import and defense against reactive oxygen species. The cell membrane must undergo remodeling to present developmentally appropriate cytokine receptors and ion transporters. In addition, erythropoiesis requires active mechanisms to prevent apoptosis and coordinate cell-cycle arrest with terminal maturation.Erythroid differentiation is highly regulated at the level of mRNA transcription, and factors controlling the expression of numerous erythroid genes, particularly globins, have been extensively characterized. Recent studies of primary hematopoietic precursors 1-6 and immortalized cell lines 7,8 are beginning to define global gene expression patterns during hematopoietic maturation, although a comprehensive view of erythropoiesis is lacking. This information is essential for new gene discovery and to better understand the regulatory networks that specify the formation and function of red blood cells. One general approach to understanding gene regulation during development is ...

Differential sensitivities of transcription factor target genes underlie cell type-specific gene expression profiles

“…These results demonstrating differential sensitivities of GATA-1 target genes (Fig. 1B) were not predictable based on the kinetics of GATA-1 target gene expression upon maximal ER-GATA-1 activation, because Gata2 repression and ␤major activation are early and late events, respectively (42).…”

The mediator complex functions as a coactivator for GATA-1 in erythropoiesis via subunit Med1/TRAP220

“…GATA-1 is also reported to associate with chromatin remodeling proteins, including the CBP/p300 histone acetyltransferase and the SWI/SNF chromatin remodeling complex (24,25). GATA-1 is able to act not only as an activator but also as a repressor (26,27). Recently, a corepressor complex that can associate with GATA-1 by FOG-1 has been identified (27,28).…”

CDC6 expression is regulated by lineage-specific transcription factor GATA1

“…In fact, transcriptional control of most of these lineages genes has been shown to depend on GATA1 activity. 15,21,22,39,40 However, final differentiation and maturation of these cells is accompanied by changes in cell proliferation and therefore in cell cycle status: megakaryocytic maturation is characterized Mutagenesis Kit (Stratagene). The DNA sequence of all mutant and/or tag-fused cDNAs were verified accordingly.…”