HOXA10, Pbx2, and Meis1 protein expression in the human endometrium: formation of multimeric complexes on HOXA10 target genes.
HOXA10 is a transcription factor necessary for embryonic uterine development and for adult endometrial receptivity. The three-amino acid loop extension family of cofactors, including Pbx and Meis, provide HOX target gene specificity in development and myeloid differentiation. Here we demonstrate the expression of Pbx and Meis family cofactors in the human endometrium and their interaction with HOXA10. Using immunohistochemical analysis, we found that Pbx2 and Meis1, but not Pbx1, Pbx3, or Meis2, were expressed in human endometrium. HOXA10, Pbx2, and Meis1 were expressed in the stroma throughout the menstrual cycle. The glandular expression of HOXA10 and Meis1 was menstrual cycle stage specific, whereas glandular Pbx2 expression did not vary. Pbx2, but not Meis1, was expressed in Ishikawa cells. EMSA demonstrated HOXA10-Pbx2 binding as a heterodimer to an enhancer of the EMX2 gene, a known target of HOXA10 regulation. Ablation of the Pbx binding site, but not ablation of the HOXA10 binding site in EMX2, resulted in loss of dimer binding. Based on the observed expression and binding patterns of Pbx2, Meis1, and HOXA10, it is likely that heterodimeric and trimeric complexes involving these proteins determine HOXA10 target gene specificity. Enhanced target gene specificity imparted by multimer binding is likely necessary for HOXA10-mediated endometrial receptivity.
Sarno
Jennifer L
JL
Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06520, USA.
Kliman
Harvey J
HJ
Taylor
Hugh S
HS
D001665:Binding Sites; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000032:analysis* / Q000235:genetics; D019281:Dimerization; D004717:Endometrium / Q000737:chemistry*; D005260:Female; D000080905:Homeobox A10 Proteins; D018398:Homeodomain Proteins / Q000032:analysis* / Q000737:chemistry / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D009154:Mutation; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins / Q000032:analysis* / Q000737:chemistry; D011518:Proto-Oncogene Proteins / Q000032:analysis* / Q000737:chemistry; D014157:Transcription Factors; D000099260:Empty Spiracles Homeobox Proteins
D004268:DNA-Binding Proteins; D000080905:Homeobox A10 Proteins; D018398:Homeodomain Proteins; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D000099260:Empty Spiracles Homeobox Proteins; C000616391:MEIS1 protein, human; C090465:PBX2 protein, human; C069634:HOXA10 protein, human