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EMBO Rep. 2016 Feb;17(2):249-65. doi: 10.15252/embr.201541465. Epub 2015 Dec 23.

Mechanism governing heme synthesis reveals a GATA factor/heme circuit that controls differentiation.

Author information

1
Department of Cell and Regenerative Biology, UW-Madison Blood Research Program, Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
2
Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
3
Department of Biochemistry, Tohoku University School of Medicine, Sendai, Japan.
4
Department of Pathology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
5
Department of Biostatistics and Medical Informatics, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA ehbresni@wisc.edu colin.dewey@wisc.edu.
6
Department of Cell and Regenerative Biology, UW-Madison Blood Research Program, Carbone Cancer Center, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA ehbresni@wisc.edu colin.dewey@wisc.edu.

Abstract

Metal ion-containing macromolecules have fundamental roles in essentially all biological processes throughout the evolutionary tree. For example, iron-containing heme is a cofactor in enzyme catalysis and electron transfer and an essential hemoglobin constituent. To meet the intense demand for hemoglobin assembly in red blood cells, the cell type-specific factor GATA-1 activates transcription of Alas2, encoding the rate-limiting enzyme in heme biosynthesis, 5-aminolevulinic acid synthase-2 (ALAS-2). Using genetic editing to unravel mechanisms governing heme biosynthesis, we discovered a GATA factor- and heme-dependent circuit that establishes the erythroid cell transcriptome. CRISPR/Cas9-mediated ablation of two Alas2 intronic cis elements strongly reduces GATA-1-induced Alas2 transcription, heme biosynthesis, and surprisingly, GATA-1 regulation of other vital constituents of the erythroid cell transcriptome. Bypassing ALAS-2 function in Alas2 cis element-mutant cells by providing its catalytic product 5-aminolevulinic acid rescues heme biosynthesis and the GATA-1-dependent genetic network. Heme amplifies GATA-1 function by downregulating the heme-sensing transcriptional repressor Bach1 and via a Bach1-insensitive mechanism. Through this dual mechanism, heme and a master regulator collaborate to orchestrate a cell type-specific transcriptional program that promotes cellular differentiation.

KEYWORDS:

Bach1; GATA factor; heme; network; transcriptome

PMID:
26698166
PMCID:
PMC5290819
DOI:
10.15252/embr.201541465
[Indexed for MEDLINE]
Free PMC Article

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