title: Mechanism governing heme synthesis reveals a GATA factor/heme circuit that controls differentiation.
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.
authors.affiliation: 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.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Tanimura
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Eli
authors.initials: E
authors.lastname: Miller
authors.affiliation: Department of Biochemistry, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Igarashi
authors.affiliation: Department of Pathology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
authors.forename: David
authors.initials: D
authors.lastname: Yang
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Judith N
authors.initials: JN
authors.lastname: Burstyn
authors.affiliation: 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.
authors.forename: Colin N
authors.initials: CN
authors.lastname: Dewey
authors.affiliation: 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.
authors.forename: Emery H
authors.initials: EH
authors.lastname: Bresnick
mesh_terms: D000624:5-Aminolevulinate Synthetase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D041905:Erythroid Cells / Q000166:cytology / Q000378:metabolism; D050982:GATA1 Transcription Factor / Q000378:metabolism*; D053263:Gene Regulatory Networks; D006410:Hematopoiesis; D006418:Heme / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D059467:Transcriptome
chemical_list: C486316:Bach1 protein, mouse; D050976:Basic-Leucine Zipper Transcription Factors; D050982:GATA1 Transcription Factor; D006418:Heme; D000624:5-Aminolevulinate Synthetase; C588337:ALAS2 protein, mouse
keywords: Bach1; GATA factor; heme; network; transcriptome