Chromatin domain activation via GATA-1 utilization of a small subset of dispersed GATA motifs within a broad chromosomal region

Abstract

Cis elements that mediate transcription factor binding are abundant within genomes, but the rules governing occupancy of such motifs in chromatin are not understood. The transcription factor GATA-1 that regulates red blood cell development binds with high affinity to GATA motifs, and initial studies suggest that these motifs are often unavailable for occupancy in chromatin. Whereas GATA-2 regulates the differentiation of all blood cell lineages via GATA motif binding, the specificity of GATA-2 chromatin occupancy has not been studied. We found that conditionally active GATA-1 (ER-GATA-1) and GATA-2 occupy only a small subset of the conserved GATA motifs within the murine ␤-globin locus. Kinetic analyses in GATA-1-null cells indicated that ER-GATA-1 preferentially occupied GATA motifs at the locus control region (LCR), in which chromatin accessibility is largely GATA-1-independent. Subsequently, ER-GATA-1 increased promoter accessibility and occupied the ␤major promoter. ER-GATA-1 increased erythroid Krü ppel-like factor and SWI͞SNF chromatin remodeling complex occupancy at restricted LCR sites. These studies revealed three phases of ␤-globin locus activation: GATA-1-independent establishment of specific chromatin structure features, GATA-1-dependent LCR complex assembly, and GATA-1-dependent promoter complex assembly. The differential utilization of dispersed GATA motifs therefore establishes spatial͞temporal regulation and underlies the multistep activation mechanism.erythropoiesis ͉ globin ͉ histone ͉ epigenetic ͉ erythoid Krü ppel-like factor

A Two-Step, PU.1-Dependent Mechanism for Developmentally Regulated Chromatin Remodeling and Transcription of the c-fms Gene

“…Based on the analysis of a number of different genes it has been suggested that enhancer elements serve as nucleation centers for the establishment of active chromatin in stem cells (30). For example, after induction of GATA-1, transcription factor complexes on the ␤-globin locus are assembled in a stepwise fashion and associate first with the upstream locus control region and only later with the promoter (14). The same is true with the VpreB1 and the 5 locus, where enhancer-but not promoter-bound transcription factor complexes early in development (29).…”

Joining the loops: β‐Globin gene regulation

“…GATA-1 can both activate and repress globin genes, but the study of this factor is complicated because of its involvement in activation and repression of many transcription factors involved in erythroid differentiation. In the mouse b-globin locus, GATA-1 binds the promoter of the b maj -gene and HS1-HS4 of the LCR (23)(24)(25). Binding of GATA-1 to the promoter and HS2, but not to HS3 and HS4, depends on the GATA-1 interacting partner FOG-1 (23,24).…”

“…In the mouse b-globin locus, GATA-1 binds the promoter of the b maj -gene and HS1-HS4 of the LCR (23)(24)(25). Binding of GATA-1 to the promoter and HS2, but not to HS3 and HS4, depends on the GATA-1 interacting partner FOG-1 (23,24). The interaction with FOG-1 is also a determining factor for the involvement of GATA-1 in different protein-complexes that can have activating or repressing functions during development (26).…”

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

“…GATA motifs are abundant in DNA and reside at most erythroid-specific genes (8,19). GATA-1 and GATA-2 occupy a small subset of the conserved GATA motifs at the ␤-globin locus with qualitatively similar patterns (13,14). Sites can differ in apparent affinities, as ␤major promoter occupancy requires a greater activity͞level of an estrogen receptor (ER) ligand binding domain fusion to GATA-1 (ER-GATA-1) vs. the locus control region (13).…”

“…GATA factors engage DNA and coregulators via a dual zinc finger domain (8), and other regions modulate activity (9,10). GATA-1 increases histone acetylation, dimethylation of histone H3 at lysine 4 (11)(12)(13), and RNA polymerase II recruitment (14) and induces higher-order chromatin changes (15).…”