PU.1 is a major downstream target of AML1 (RUNX1) in adult mouse hematopoiesis

Abstract

Both PU.1 (also called SFPI1), an Ets-family transcription factor, and AML1 (also called RUNX1), a DNA-binding subunit of the CBF transcription factor family, are crucial for the generation of all hematopoietic lineages, and both act as tumor suppressors in leukemia. An upstream regulatory element (URE) of PU.1 has both enhancer and repressor activity and tightly regulates PU.1 expression. Here we show that AML1 binds to functionally important sites within the PU.1 upstream regulatory element and regulates PU.1 expression at both embryonic and adult stages of development. Analysis of mice carrying conditional AML1 knockout alleles and knock-in mice carrying mutations in all three AML1 sites of the URE proximal region demonstrated that AML1 regulates PU.1 both positively and negatively in a lineage dependent manner. Dysregulation of PU.1 expression contributed to each of the phenotypes observed in these mice, and restoration of proper PU.1 expression rescued or partially rescued each phenotype. Thus, our data demonstrate that PU.1 is a major downstream target gene of AML1.

PU.1 is regulated by NF-κB through a novel binding site in a 17 kb upstream enhancer element

“…Also, a PU.1 binding site in the PHR of the URE was reported to activate PU.1 in a self-regulatory manner (Okuno et al, 2005). In addition, two CEBPA sites have NF-jB regulates PU.1 through a distal element N Bonadies et al been described in the PHR of the URE (Yeamans et al, 2007), and three RUNX1/AML1 sites appear to be present in the PHR (Huang et al, 2008). Our findings add NF-kB to this list of factors affecting activation of PU.1 expression through this distal regulatory element.…”

Transcriptional control of granulocyte and monocyte development

“…PU.1 binds and activates its own promoter and distal enhancer, potentially to variable degrees in different lineages and developmental stages dependent on cooperating factors (Chen et al, 1995b;Okuno et al, 2005). Onset of PU.1 expression in HSC or LMP may depend on Runx1-mediated activation via the PU.1 distal enhancer (Huang et al, 2007a), with C/EBPa then directing LMP or CMP to the GMP stage and beyond, in part, via further PU.1 induction. The C/EBPb and PU.1 DNA-binding domains directly interact (Yang et al, 2000), and promoter-bound C/EBPb increases PU.1 interaction with a nearby cis element in the IL-1b promoter, augmenting gene induction (Grondin et al, 2007).…”

Bcl11b and combinatorial resolution of cell fate in the T-cell gene regulatory network

“…This balance is tipped during commitment, with the silencing of the phase 1 regulatory genes and down-regulation of Kit, but only limited aspects of this process are understood. GATA-3, Runx1, and TCF-1 (or its relative LEF-1) eventually play roles in silencing expression of phase 1 regulatory genes encoding PU.1 and Bcl11a during commitment, as demonstrated by gain-and loss-offunction data (27,(36)(37)(38)(39) (Fig. 1B).…”