title: Differential activity of the FGF-4 enhancer in F9 and P19 embryonal carcinoma cells.
abstract: Transcription factors Oct-3/4 and Sox2 behave as global regulators during mammalian embryogenesis. They work together by binding co-operatively to closely spaced HMG and POU motifs (HMG/POU cassettes). Recently, it was suggested that a critical Sox2:Oct-3/4 target gene, FGF-4, is expressed at lower levels in P19 than in F9 embryonal carcinoma (EC) cells, due to lower levels of Sox2 in P19 than in F9 cells. We tested this possibility to better understand how FGF-4 expression is modulated during development. Although we found that P19 EC cells express approximately 10-fold less FGF-4 mRNA than F9 EC cells, we determined that Sox2 levels do not differ markedly in F9 and P19 EC cells. We also determined that Sox2 and Oct-3/4 work together equally well in both EC cell lines. Moreover, in contrast to an earlier prediction based on in vitro binding studies, we demonstrate that the function of the HMG/POU cassettes of the FGF-4 and UTF1 genes does not differ significantly in these EC cell lines when tested in the context of a natural enhancer. Importantly, we determined that the FGF-4 promoter is highly responsive to a heterologous enhancer in both EC cell lines; whereas, the FGF-4 enhancer is 7- to 10-fold less active in P19 than in F9 EC cells. Because F9 and P19 EC cells are likely to represent cells at different stages of mammalian development, we suggest that this difference in FGF-4 enhancer activity may reflect a mechanism used to decrease, but not abolish, FGF-4 expression as the early embryo develops.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Boer
authors.forename: Cory T
authors.initials: CT
authors.lastname: Bernadt
authors.forename: Michelle
authors.initials: M
authors.lastname: Desler
authors.forename: Phillip J
authors.initials: PJ
authors.lastname: Wilder
authors.forename: Janel L
authors.initials: JL
authors.lastname: Kopp
authors.forename: Angie
authors.initials: A
authors.lastname: Rizzino
mesh_terms: D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology; D024202:Electrophoretic Mobility Shift Assay; D004742:Enhancer Elements, Genetic / Q000235:genetics / Q000502:physiology*; D051519:Fibroblast Growth Factor 4 / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D024742:HMG-Box Domains / Q000235:genetics; D051379:Mice; D009373:Neoplasms, Germ Cell and Embryonal / Q000737:chemistry / Q000235:genetics / Q000473:pathology* / Q000503:physiopathology*; D050814:Octamer Transcription Factor-3 / Q000032:analysis / Q000235:genetics / Q000502:physiology; D050809:POU Domain Factors / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D055748:SOXB1 Transcription Factors; D015534:Trans-Activators / Q000032:analysis / Q000235:genetics / Q000502:physiology; D014162:Transfection
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; C496446:Fgf4 protein, mouse; D051519:Fibroblast Growth Factor 4; D050814:Octamer Transcription Factor-3; D050809:POU Domain Factors; D012333:RNA, Messenger; D055748:SOXB1 Transcription Factors; C527783:Sox2 protein, mouse; D015534:Trans-Activators; C112198:Utf1 protein, mouse