Functional dissection of the ETS transcription factor MEF

Myeloid ELF1-like factor (MEF), also known as ELF4, is a member of the ETS family of transcription factors which is expressed in hematopoietic cells. MEF-deficient mice have defects in natural killer cell and natural killer T cell development, suggesting a role for MEF in regulating innate immunity. MEF also functions in myeloid cells, where it can transactivate target genes. To identify MEF target genes in a "myeloid" environment, we created an inducible expression system and used oligonucleotide microarrays to examine the transcript profile of HEL cells after induction of MEF expression. Sixteen genes were reproducibly turned on or off more than 2-fold, 8 h after induction of MEF expression, and we examined one of the genes, interleukin-8 (IL-8), in greater detail. IL-8 is a CXC chemokine involved in neutrophil chemoattraction, angiogenesis, and stem cell mobilization. It is expressed by several tumor types, and its expression is regulated primarily transcriptionally. The IL-8 promoter contains three ETS binding sites, and we identified the specific site that binds MEF and is required for MEF responsiveness. MEF, but not the closely related ETS factors PEA3, ETS1, ETS2, ELF1, or PU.1, strongly activates the IL-8 promoter. MEF overexpression is sufficient to induce IL-8 protein expression, and reduction in MEF expression (using RNA interference) results in decreased IL-8 levels. These data demonstrates that MEF is an important regulator of IL-8 expression.Myeloid ELF1-like factor (MEF), 1 also known as ELF4, is a member of the ETS family of transcriptional regulators and was originally isolated from a myeloid hematopoietic cell line (1). ETS proteins generally regulate transcription in coordination with other transcription factors, binding the core ETS binding sequence GGAA, via their ETS domain. Because this sequence occurs frequently in genomic DNA, the identification of true ETS target genes has been difficult. Furthermore, the significant homology in the ETS domains of these proteins makes it daunting to determine which ETS factor regulates a particular gene in vivo. Although cytokine and cytokine receptor genes and many other genes have been proposed as targets of various ETS factors (for review, see Ref.2), their validation as in vivo targets has rarely been performed.Microarrays have been used extensively to profile the transcripts expressed in tumor or normal tissue, both as a way to define their biology and also to determine which genes serve as determinants for their classification. We and others have used microarrays to identify genes regulated by particular transcription factors such as C/EBP␣ (3), c-Myc (4), WT-1 (5), and BRCA-1 (6), among others. These studies have identified target genes not previously described and have failed to find gene targets previously identified by reporter gene assays. Thus, subsequent validation of direct (and indirect) targets will generally require the use of multiple additional approaches to confirm the results.MEF is a member of the Drosophila E74 subfamily of ETS p...

Section: Discussioncontrasting

confidence: 76%

Myeloid ELF1-like Factor Is a Potent Activator of Interleukin-8 Expression in Hematopoietic Cells

Hedvat

Yao²,

Sokolic

et al. 2004

“…6, A and B). Consistent with what we previously showed (40), MEF was strongly expressed in the nucleus, whereas it was barely detected in the cytoplasmic fraction despite that the protein amount loaded for the latter was 10 times more than the nuclear extract. At longer exposures, we observed that MEF expression in the cytoplasm was also down-regulated by MDM2 (Fig.…”

Section: Mdm2 Interacts With and Down-regulates Mef Expression And Stsupporting

confidence: 91%

“…observation considering that MEF is known to be constitutively nuclear localizing and is barely detected in the cytoplasm (18,40) (Fig. 6, A and C).…”

Section: Discussionmentioning

confidence: 81%

The Transcription Factor MEF/Elf4 Is Dually Modulated by p53-MDM2 Axis and MEF-MDM2 Autoregulatory Mechanism

Suico

Fukuda

Miyakita

et al. 2014

Self Cite

Background:The ETS transcription factor myeloid elf-1-like factor (MEF) activates some genes including lysozyme, interleukin-8, and MDM2, and also influences the cell cycle. Results: MEF protein expression and stability is suppressed by MDM2 in p53-dependent and -independent manner. Conclusion: MEF is targeted by MDM2 for degradation. Significance: The previously unrecognized MEF-MDM2-p53 axis highlights a regulatory balance of these transcription factors.

“…We have previously demonstrated that MEF up-regulates lysozyme gene expression in epithelial cells (24). We also found that MEF is constitutively localized in the nucleus under normal or stress conditions (25).…”

mentioning

confidence: 77%

Myeloid Elf-1-like Factor, an ETS Transcription Factor, Up-regulates Lysozyme Transcription in Epithelial Cells through Interaction with Promyelocytic Leukemia Protein

Suico

Yoshida

Seki

et al. 2004

Self Cite

Myeloid elf-1-like factor (MEF) or Elf4, which is a member of the ETS transcription factor family, up-regulates the basal expression of lysozyme gene in epithelial cells and is constitutively localized in the nucleus. The mammalian cell nucleus is organized into distinct nuclear domains or compartments that are essential for diverse physiological processes. Promyelocytic leukemia (PML) nuclear body or nuclear domain 10 is one of the nuclear domains and is involved in tumor suppression and regulation of transcription. Here, we investigate the role of PML nuclear body in MEF transactivation. We show that PML, but not Sp100, induced the accumulation of MEF in PML nuclear bodies and that MEF and PML physically interacted. This interaction stimulated MEF transcriptional activity, resulting in the up-regulation of endogenous lysozyme expression. Amino acids 348 -517 of MEF were required for the accumulation of MEF in PML nuclear bodies and up-regulation of lysozyme transcription, which is enhanced by PML. Moreover, the C-terminal region of MEF spanning amino acids 477-517 was the putative region required for interaction between MEF and PML as determined with the use of the mammalian twohybrid system. In addition, heat-shock treatment induced the accumulation of MEF in endogenous PML nuclear bodies and enhanced MEF transactivation of lysozyme gene. Thus, the recruitment of MEF to PML nuclear bodies may partly regulate lysozyme transcription in epithelial cells.The mammalian cell nucleus contains a large number of specialized nuclear domains or compartments. Each nuclear domain has been reported to relate with various physiological processes, such as transcription, DNA replication and pre-mRNA splicing (1). PML 1 nuclear body (also called nuclear domain 10 and promyelocytic leukemia protein oncogenic domain) is one of the nuclear domains (1-3). PML NBs have been reported to vary in size from 0.2 to 1.0 m in diameter, and a typical mammalian nucleus contains 10 -30 of these nuclear bodies (2, 4). Two major components, PML and Sp100, are considered to build the framework of PML nuclear bodies (5). PML was identified as part of a fusion protein with retinoic acid receptor ␣, resulting from the t(15;17) chromosomal translocation expressed in acute promyelocytic leukemia (6, 7). Sp100 was first characterized as an autoantigen in certain autoimmune disorders (8). Although PML and Sp100 are core components of PML nuclear bodies, numerous proteins, such as p53, SUMO-1, CBP, HDAC, Daxx, pRB, and HIPK2, seem to transiently localize to PML nuclear bodies (4, 9 -12). A variety of functions has been suggested for PML nuclear bodies, including tumor suppression and transcriptional regulation through the titration, modification, and compartmentalization of proteins (4, 9). The ETS transcription factor family has more than 30 members, and a number of these factors have been shown to play roles in important physiological processes, including cellular proliferation, differentiation, development, hematopoiesis, angiogenesis, and transform...