Synergistic activity of STAT3 and c-Jun at a specific array of DNA elements in the alpha(2)-macroglobulin promoter

The transcriptional activity of natural promoters is sensitive to the preci se spatial arrangement of DNA elements and their incorporation into higher order DNA-protein complexes. STAT3 and c-Jun form a specific ternary comple x in vitro with a synthetic DNA element containing AP1 and SIE sites. These associations are critical for synergistic activation of transcription from a synthetic promoter by STAT3 and c-Jun. Expression of the acute phase pro tein alpha (2)-macroglobulin is induced in vivo by interleukin-6 (IL-6)-rel ated cytokines; we demonstrate that coordinate interactions among STAT3, c- Jun, and a specific array of DNA elements contribute to activation of the a lpha (2)-macroglobulin promoter in response to IL-6 family members. At leas t five promoter elements are involved in activation: two AP1 sites at -113 to -107 and -152 to -140, an acute phase response element (APRE (SIE)) at - 171 to -163, and two AT-rich regions at -143 to -138 and -128 to -123. Syne rgism between STAT3 or STAT3-C and c-Jun is impaired by mutation of the APR E (SIE) or either AP1 site, as well as by mutations that alter the AT-rich regions or their phasing. Mutations of STAT3 previously shown to disrupt ph ysical and functional interactions with c-Jun do not impair synergy between STAT3-C and c-Jun at the alpha2-macroglobulin promoter in HepG2 cells, sug gesting that STAT3-C and STAT3 differ with respect to their precise contact s with c-Jun.