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Identification of E74-like factor 1 (ELF1) as a transcriptional regulator of the Hox cofactor MEIS1.

ABSTRACT: OBJECTIVE:Myeloid ectropic viral integration site 1 (MEIS1) is a Hox cofactor known for its role in development and is strongly linked to normal and leukemic hematopoiesis. Although previous studies have focused on identifying protein partners of MEIS1 and its transcriptionally regulated targets, little is known about the upstream transcriptional regulators of this tightly regulated gene. Understanding the regulation of MEIS1 is important to understanding normal hematopoiesis and leukemogenesis. MATERIALS AND METHODS:Here we describe our studies focusing on the evolutionary conserved putative MEIS1 promoter region. Phylogenetic sequence analysis and reporter assays in MEIS1-expressing (K562) and nonexpressing (HL60) leukemic cell line models were used to identify key regulatory regions and potential transcription factor binding sites within the candidate promoter region followed by functional and expression studies of one identified regulator in both cell lines and primary human cord blood and leukemia samples. RESULTS:Chromatin status of MEIS1 promoter region is associated with MEIS1 expression. Truncation and mutation studies coupled with reporter assays revealed that a conserved ETS family member binding site located 289 bp upstream of the annotated human MEIS1 transcription start site is required for promoter activity. Of the three ETS family members tested, only ELF1 was enriched on the MEIS1 promoter as assessed by both electrophoretic mobility shift assay and chromatin immunoprecipitation experiments in K562. This finding was confirmed in MEIS1-expressing primary human samples. Moreover, small interfering RNA-mediated knockdown of ELF1 in K562 cells was associated with a decreased MEIS1 expression. CONCLUSIONS:We conclude that the ETS transcription factor ELF1 is an important positive regulator of MEIS1 expression.

SUBMITTER: Xiang P

PROVIDER: S-EPMC3887005 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Identification of E74-like factor 1 (ELF1) as a transcriptional regulator of the Hox cofactor MEIS1.

Xiang Ping P Lo Chaoyu C Argiropoulos Bob B Lai C Benjamin CB Rouhi Arefeh A Imren Suzan S Jiang Xiaoyan X Mager Dixie D Humphries R Keith RK

Experimental hematology 20100623 9

<h4>Objective</h4>Myeloid ectropic viral integration site 1 (MEIS1) is a Hox cofactor known for its role in development and is strongly linked to normal and leukemic hematopoiesis. Although previous studies have focused on identifying protein partners of MEIS1 and its transcriptionally regulated targets, little is known about the upstream transcriptional regulators of this tightly regulated gene. Understanding the regulation of MEIS1 is important to understanding normal hematopoiesis and leukemo ...[more]

PMID: 20600580

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Project description:IntroductionThe principal voltage-gated Na+ channel, NaV1.5 governs heart excitability and conduction. NaV1.5 dysregulation is responsible for ventricular arrhythmias and subsequent sudden cardiac death (SCD) in post-infarct hearts. The transcription factor Meis1 performs a significant role in determining differentiation fate and regenerative capability of cardiomyocytes. However, the functions of Meis1 in ischemic arrhythmias following myocardial infarction (MI) are still largely undefined.ObjectivesHere we aimed to study whether Meis1 could act as a key regulator to mediate cardiac Na+ channel and its underlying mechanisms.MethodsHeart-specific Meis1 overexpression was established by AAV9 virus injection in C57BL/6 mice. The QRS duration, the incidence of ventricular arrhythmias and cardiac conduction velocity were evaluated by ECG, programmed electrical stimulation and optical mapping techniques respectively. The conventional patch clamp technique was performed to explore the INa characteristics of isolated mouse ventricular myocytes. In vitro, Meis1 was also overexpressed in hypoxic-treated neonatal cardiomyocytes. The analysis of immunoblotting and immunofluorescence were used to detect the changes in the expression of NaV1.5 in each group.ResultsWe found that forced expression of Meis1 rescued the prolongation of QRS complex, produced anti-arrhythmic activity and improved epicardial conduction velocity in infarcted mouse hearts. In terms of mechanisms, cardiac electrophysiological changes of MI mice can be ameliorated by the recovery of Meis1, which is characterized by the restoration of INa current density and NaV1.5 expression level of cardiomyocytes in the marginal zone of MI mouse hearts. Furthermore, in vitro studies showed that Meis1 was also able to rescue hypoxia-induced decreased expression and dysfunction of NaV1.5 in ventricular myocytes. We further revealed that E3 ubiquitin ligase CDC20 led to the ubiquitination and degradation of Meis1, which blocked the transcriptional regulation of SCN5A by Meis1 and ultimately led to the electrophysiological remodeling in ischemic-hypoxic cardiomyocytes.ConclusionCDC20 mediates ubiquitination of Meis1 to govern the transcription of SCN5A and cardiac electrical conduction in mouse cardiomyocytes. This finding uncovers a new mechanism of NaV1.5 dysregulation in infarcted heart, and provides new therapeutic strategies for malignant arrhythmias and sudden cardiac death following MI.

Project description:Homeobox transcription factors Meis1 and Hoxa9 promote hematopoietic progenitor self-renewal and cooperate to cause acute myeloid leukemia (AML). While Hoxa9 alone blocks the differentiation of nonleukemogenic myeloid cell-committed progenitors, coexpression with Meis1 is required for the production of AML-initiating progenitors, which also transcribe a group of hematopoietic stem cell genes, including Cd34 and Flt3 (defined as Meis1-related leukemic signature genes). Here, we use dominant trans-activating (Vp16 fusion) or trans-repressing (engrailed fusion) forms of Meis1 to define its biochemical functions that contribute to leukemogenesis. Surprisingly, Vp16-Meis1 (but not engrailed-Meis1) functioned as an autonomous oncoprotein that mimicked combined activities of Meis1 plus Hoxa9, immortalizing early progenitors, inducing low-level expression of Meis1-related signature genes, and causing leukemia without coexpression of exogenous or endogenous Hox genes. Vp16-Meis1-mediated transformation required the Meis1 function of binding to Pbx and DNA but not its C-terminal domain (CTD). The absence of endogenous Hox gene expression in Vp16-Meis1-immortalized progenitors allowed us to investigate how Hox alters gene expression and cell biology in early hematopoietic progenitors. Strikingly, expression of Hoxa9 or Hoxa7 stimulated both leukemic aggressiveness and transcription of Meis1-related signature genes in Vp16-Meis1 progenitors. Interestingly, while the Hoxa9 N-terminal domain (NTD) is essential for cooperative transformation with wild-type Meis1, it was dispensable in Vp16-Meis1 progenitors. The fact that a dominant transactivation domain fused to Meis1 replaces the essential functions of both the Meis1 CTD and Hoxa9 NTD suggests that Meis-Pbx and Hox-Pbx (or Hox-Pbx-Meis) complexes co-occupy cellular promoters that drive leukemogenesis and that Meis1 CTD and Hox NTD cooperate in gene activation. Chromatin immunoprecipitation confirmed co-occupancy of Hoxa9 and Meis1 on the Flt3 promoter.

Dataset Information

Identification of E74-like factor 1 (ELF1) as a transcriptional regulator of the Hox cofactor MEIS1.

Publications

Identification of E74-like factor 1 (ELF1) as a transcriptional regulator of the Hox cofactor MEIS1.

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