Heterodimerization of c-Jun with ATF-2 and c-Fos is required for positive and negative regulation of the human urokinase enhancer

Oncogene. 1995 Jul 20;11(2):365-76.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Activating Transcription Factor 2
  • Base Sequence
  • Binding Sites
  • Cyclic AMP Response Element-Binding Protein / chemistry*
  • Cyclic AMP Response Element-Binding Protein / metabolism*
  • Enhancer Elements, Genetic / physiology*
  • Humans
  • Leucine Zippers / physiology
  • Molecular Sequence Data
  • Phorbol Esters / pharmacology
  • Protein Conformation / drug effects
  • Proto-Oncogene Proteins c-fos / chemistry*
  • Proto-Oncogene Proteins c-fos / metabolism*
  • Proto-Oncogene Proteins c-jun / chemistry*
  • Proto-Oncogene Proteins c-jun / metabolism*
  • Transcription Factors / metabolism*
  • Transcription, Genetic / physiology
  • Urokinase-Type Plasminogen Activator / genetics*
  • Urokinase-Type Plasminogen Activator / metabolism*

Substances

  • ATF2 protein, human
  • Activating Transcription Factor 2
  • Cyclic AMP Response Element-Binding Protein
  • Phorbol Esters
  • Proto-Oncogene Proteins c-fos
  • Proto-Oncogene Proteins c-jun
  • Transcription Factors
  • Urokinase-Type Plasminogen Activator