TAF7 (TAFII55) Plays a Role in the Transcription Activation by c-Jun

c-Jun is a member of the AP-1 family of transcription factors regulating expression of specific target genes in a variety of cellular processes including proliferation, stress response, and tumorigenicity. In the present study we have analyzed the mechanism of c-Jun function as a transactivator with respect to members of the basal transcription machinery, TATA-binding proteinassociated factors (TAFs). We show that one member of the family, human TAF7 (formerly TAF II 55), physically interacts with c-Jun through two independent interaction domains, within the N-and C-terminal part of c-Jun. Interaction in vitro correlates with enhanced transactivation function of c-Jun in HEK293 and COS cells in the presence of increasing amounts of TAF7. TAF7 interacts preferentially with DNA-bound phosphorylated c-Jun, suggesting that TAF7 represents a novel c-Jun co-activator mediating activation of AP-1 target genes in response to extracellular signals.