Setd1a and NURF mediate chromatin dynamics and gene regulation during erythroid cell differentiation

The modulation of chromatin structure is a key step in transcription regulation in eukaryotic cells. Mammalian erythropoiesis is accompanied by dynamic alterations in chromatin structure and gene expression, but the epigenetic regulators that modulate and coordinate these changes are largely unknown. USF, Setd1a and NURF complexes interact to regulate chromatin architecture in erythropoiesis, but the basis for this regulation is unknown. We studied this process using both murine and human models of erythropoiesis. In human primary erythroid cells, H3K4me3, USF1/2, and BPTF, a component of the NURF complex, were significantly co-enriched at more than 50% of transcription start sites (TSSs) of erythroid genes, associated with repositioning of promoter- or enhancer-associated nucleosomes. Depletion of Setd1a, an H3K4 trimethylase, led to a reduction of promoter-associated H3K4 methylation, inhibition of gene transcription and blockade of erythroid differentiation. This was associated with alterations in NURF complex-mediated nucleosome repositioning at erythroid gene promoters and chromatin accessibility. Setd1a deficiency caused decreased associations between the LCR and the -major globin promoter as well as reduced expression of the adult β-globin gene. In vivo, mice deficient for Setd1a in the erythroid compartment resulted in reduced Ter119/CD71 positive bone marrow erythroblasts, peripheral blood RBCs, and hemoglobin levels. These data indicate that Setd1a and NURF complexes coordinately regulate erythroid promoter chromatin dynamics during erythroid differentiation. CD34+-selected stem and progenitor cells were expanded for three days in the absence of EPO. The cells were further cultured in the presence of EPO, and formaldehyde crosslinked chromatin was isolated after cells differentiated into R3/R4 nucleated erythroid cells. Chromatin Immunoprecipitation followed by sequencing (chIP-seq) was performed using antibodies against BPTF, SET1, USF1 and USF2.