Heterodimerization of c-Jun with ATF-2 and c-Fos is required for positive and negative regulation of the human urokinase enhancer.
Dimerization plays a pivotal role in modulating the activity of the c-Jun proto-oncogene product. Heterodimerization with activating transcription factor-2 (ATF-2) alters the DNA-binding specificity of c-Jun, allowing its targeting to several cAMP responsive element (CRE)-related sequences, which control a subset of AP-1-responsive genes. Here we show that a c-Jun/ATF-2 heterodimer binds to the AP-1 site (uPA 5'-TRE) essential for the activity of the human urokinase enhancer, conferring on this element several distinctive regulatory properties. The c-Jun/ATF-2 heterodimer was identified by binding competition assays, u.v. cross linking, and monospecific antibodies. In vitro binding studies revealed that the uPA 5'-TRE sequence is recognized by the cyclic AMP-unresponsive ATF-2 factor, but not by the cyclic AMP-inducible CREB. In addition, in vivo studies suggest that ATF-2 can mediate, at the same time, the activation of the c-Jun/ATF-2 site and the repression of the canonical collagenase AP-1 site. We report that heterodimerization with c-Fos does not increase the binding of c-Jun to the uPA 5'-TRE, in contrast to the increased binding at a consensus AP-1 site. Our data further suggest that c-Fos can act as a repressor of the c-Jun/ATF-2 binding site, revealing an important functional difference, with respect to canonical AP-1 elements.
De Cesare
D
D
International Institute of Genetics and Biophysics, Naples, Italy.
Vallone
D
D
Caracciolo
A
A
Sassone-Corsi
P
P
Nerlov
C
C
Verde
P
P
D051698:Activating Transcription Factor 2; D001483:Base Sequence; D001665:Binding Sites; D017362:Cyclic AMP Response Element-Binding Protein / Q000737:chemistry* / Q000378:metabolism*; D004742:Enhancer Elements, Genetic / Q000502:physiology*; D006801:Humans; D016350:Leucine Zippers / Q000502:physiology; D008969:Molecular Sequence Data; D010703:Phorbol Esters / Q000494:pharmacology; D011487:Protein Conformation / Q000187:drug effects; D000090063:Proto-Oncogene Mas; D016760:Proto-Oncogene Proteins c-fos / Q000737:chemistry* / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000737:chemistry* / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics* / Q000378:metabolism*
C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; D017362:Cyclic AMP Response Element-Binding Protein; C000715470:MAS1 protein, human; D010703:Phorbol Esters; D000090063:Proto-Oncogene Mas; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; D014568:Urokinase-Type Plasminogen Activator