title: 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.
  
  
  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.
authors.affiliation: Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver, British Columbia, Canada.
authors.forename: Ping
authors.initials: P
authors.lastname: Xiang
authors.forename: Chaoyu
authors.initials: C
authors.lastname: Lo
authors.forename: Bob
authors.initials: B
authors.lastname: Argiropoulos
authors.forename: C Benjamin
authors.initials: CB
authors.lastname: Lai
authors.forename: Arefeh
authors.initials: A
authors.lastname: Rouhi
authors.forename: Suzan
authors.initials: S
authors.lastname: Imren
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Jiang
authors.forename: Dixie
authors.initials: D
authors.lastname: Mager
authors.forename: R Keith
authors.initials: RK
authors.lastname: Humphries
mesh_terms: D005312:Fetal Blood / Q000378:metabolism*; D015973:Gene Expression Regulation, Leukemic; D055785:Gene Knockdown Techniques; D018922:HL-60 Cells; D018398:Homeodomain Proteins / Q000096:biosynthesis*; D006801:Humans; D020014:K562 Cells; D007938:Leukemia / Q000378:metabolism*; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D020218:Response Elements; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C512897:ELF1 protein, human; D018398:Homeodomain Proteins; C000616391:MEIS1 protein, human; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors