Oct-1 specifically binds the UEF4 site of the human AP1-regulated urokinase enhancer.
The inducible urokinase enhancer contains three essential elements: a combined PEA3/AP1 and a downstream AP1 site, separated by a 74-bp DNA region called COM (cooperation mediator), that is required for the synergism between the three sites. The 5' half of COM (uCOM) forms four retarded complexes with HeLa or HepG2 nuclear proteins (UEF1-4). We now demonstrate that the UEF4 complex is the transcription factor Oct-1. Because of functional redundancy of the UEF sites, single mutations in UEF4 have no phenotype; we have changed UEF4 from a low to a high affinity binding site for Oct-1. In vitro, this mutation increases the DNA binding of Oct-1 and disturbs the binding of the Prep-Pbx complexes to the nearby UEF3 site. In vivo, this mutation reduces the basal transcriptional activity of the urokinase enhancer, while not affecting its phorbol ester inducibility. This is in keeping with the effect of the deletions of the COM region, which result in an increase in the basal level and, as a consequence, in the loss of 4beta-phorbol 12-myristate 13-acetate inducibility. Oct-1 therefore is not involved in the inducibility of the urokinase enhancer but only in determining its basal activity level.
Palazzolo
M
M
Università Vita-Salute S. Raffaele, Department of Molecular Pathology and Medicine, Molecular Genetics Unit, DIBIT, Milan, Italy.
Berthelsen
J
J
De Cesare
D
D
Blasi
F
F
D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004247:DNA; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D051863:Host Cell Factor C1; D006801:Humans; D007136:Immunoglobulins / Q000235:genetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D050811:Octamer Transcription Factor-1; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D018808:Transcription Factor AP-1 / Q000737:chemistry / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics*
D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; D051863:Host Cell Factor C1; D007136:Immunoglobulins; D050811:Octamer Transcription Factor-1; C494165:POU2F1 protein, human; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D004247:DNA; D014568:Urokinase-Type Plasminogen Activator