Fibroblast growth factor receptor 4 is a target for the zinc-finger transcription factor Ikaros in the pituitary.
Fibroblast growth factor receptors (FGFRs) have been implicated in a multitude of endocrine cell hormonal and proliferative properties, and FGFR4 is differentially expressed in normal and neoplastic pituitary. We therefore examined the functionally important cis-DNA elements and multiprotein complexes implicated in the cooperative control of expression of the human FGFR4 gene in pituitary cells. Using deletional mapping, we defined a 214-bp (-115/+99) promoter that was functional in pituitary GH4 and PRL 235 cells. Overlapping 40- to 50-bp fragments of this minimal promoter were examined by EMSA. Interestingly, fragment C (-64/-26) included potential binding sites for the hematopoietic zinc finger-containing transcription factor Ikaros (Ik) flanked by binding sites for Sp and Ets-type factors. DNA binding by Ik, Sp, and Ets-like factors was confirmed by oligonucleotide competition and supershifting with specific antibodies. Transcriptional regulation of FGFR4 by Ik was demonstrated by cotransfection of Ik1 with or without Sp1 or Ets overexpression and by disruption of the Ik binding site. Although both Ets-1 and Sp1 overexpression stimulated promoter activity, mutation of the Ik-binding site completely eliminated the Ik1 effect. Specific Ik expression was identified by Western blotting of pituitary GH4 and PRL235 cells and localized in primary mouse hormone-producing anterior pituitary cells by immunocytochemistry. Our findings point to a new role for Ik outside the hematopoietic system and suggest a novel transcriptional contribution with Ets and Sp1 in regulation of FGFR4 in the pituitary.
Yu
ShunJiang
S
Department of Medicine, Mount Sinai Hospital and University of Toronto, Toronto, Ontario, Canada M5G 2M9.
Asa
Sylvia L
SL
Ezzat
Shereen
S
D016475:3T3 Cells; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D015153:Blotting, Western; D002460:Cell Line; D002874:Chromosome Mapping; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins; D017353:Gene Deletion; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D051740:Ikaros Transcription Factor; D007150:Immunohistochemistry; D051379:Mice; D016297:Mutagenesis, Site-Directed; D010902:Pituitary Gland / Q000378:metabolism*; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D010911:Pituitary Neoplasms; D011401:Promoter Regions, Genetic; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology; D050783:Proto-Oncogene Proteins c-ets; D051381:Rats; D017468:Receptors, Fibroblast Growth Factor / Q000235:genetics*; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D014162:Transfection; D014407:Tumor Cells, Cultured; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; C494041:ETS1 protein, human; C494042:Ets1 protein, mouse; C494043:Ets1 protein, rat; C497239:IKZF1 protein, human; D050784:Proto-Oncogene Protein c-ets-1; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D017468:Receptors, Fibroblast Growth Factor; D016329:Sp1 Transcription Factor; D014157:Transcription Factors; C497238:Zfpn1a1 protein, mouse; D051740:Ikaros Transcription Factor; D004247:DNA