A Novel Complex, RUNX1-MYEF2, Represses Hematopoietic Genes in Erythroid Cells

Abstract

RUNX1 is known to be an essential transcription factor for generating hematopoietic stem cells (HSC), but much less is known about its role in the downstream process of hematopoietic differentiation. RUNX1 has been shown to be part of a large transcription factor complex, together with LDB1, GATA1, TAL1, and ETO2 (N. Meier et al., Development 133 :4913–4923, 2006) in erythroid cells. We used a tagging strategy to show that RUNX1 interacts with two novel protein partners, LSD1 and MYEF2, in erythroid cells. MYEF2 is bound in undifferentiated cells and is lost upon differentiation, whereas LSD1 is bound in differentiated cells. Chromatin immunoprecipitation followed by sequencing (ChIP-seq) and microarray expression analysis were used to show that RUNX1 binds approximately 9,000 target sites in erythroid cells and is primarily active in the undifferentiated state. Functional analysis shows that a subset of the target genes is suppressed by RUNX1 via the newly identified partner MYEF2. Knockdown of Myef2 expression in developing zebrafish results in a reduced number of HSC.

The C-terminus of CBFβ-SMMHC is required to induce embryonic hematopoietic defects and leukemogenesis

“…4 of these genes (CD53, 20 Cpa3, 20 ItgaL, 21,22 Mpo 23,24 ) are targets of RUNX1 and many of these genes are deregulated in other models of impaired RUNX1 activity. 4,25,26 These findings imply that at least some of the gene expression changes induced by CBF␤-SMMHC⌬C95 are because of altered RUNX1 activity.…”

“…4 of these genes (CD53, 20 Cpa3, 20 ItgaL,21,22 Mpo 23,24 ) are targets of RUNX1 and many of these genes are deregulated in other models of impaired RUNX1 activity. 4,25,26 These findings imply that at least some of the gene expression changes induced by CBF␤-SMMHC⌬C95 are because of altered RUNX1 activity.The data presented here demonstrate that the C-terminal 95 amino acids are critical for CBF␤-SMMHC's activities, particularly leukemogenesis. Blocking the function of this region in the fusion protein may be a potential therapeutic strategy in the future for the treatment of Inv16 AML.…”

GATA2 is required for HSC generation and survival

“…Our results show for the first time that GATA2 is required for HSC generation in the AGM and continues to be required for HSC survival. GATA2 is thought to act in combination with other transcription factors, such as RUNX1, to promote/ enhance transcription of genes relevant to hematopoietic cell development and growth (Wilson et al, 2010;van Riel et al, 2012). Because we used the Vec-Cre and Vav-Cre cKO approach used previously for Runx1 deletion (Chen et al, 2009), the requirements for these two transcription factors can be directly compared.…”

“…Yet, it is unknown whether GATA2 is required in the endothelial compartment for the formation of intra-arterial clusters and AGM HSCs, and what the function of GATA2 is thereafter. Furthermore, GATA factors are described to act through combinatory interactions with other key regulators, including RUNX1 (Wilson et al, 2010;van Riel et al, 2012). Previously, RUNX1 was shown to be required for the generation of HSCs during the endothelial-to-hematopoietic transition (EHT).…”

Epigenetic control of hematopoiesis: the PU.1 chromatin connection

“…For example, several essential myeloid lineage growth factor receptor genes, such as those encoding the M-CSFR and GM-GSFRα, are regulated by a PU.1 collaboration with C/EBPα (Hohaus et al, 1995;Li et al, 2005). Runx1 is a critical factor for the development of the definitive HSC pool and also has a role in the specification of some hematopoietic lineages (Wang et al, 1996;van Riel et al, 2012). Similar to the PU.1-C/EBPα complex, PU.1 also collaborates with Runx1 to activate transcription of the Csf1r gene encoding the M-CSF receptor (Li et al, 2005).…”