SELECTIVE DNA BENDING BY A VARIETY OF BZIP PROTEINS

We have investigated DNA bending by bZIP family proteins that can bind to the AP-1 site. DNA bending is widespread, although not universal, among members of this family. Different bZIP protein dimers induced di stinct DNA bends. The DNA bend angles ranged from virtually 0 to great er than 40-degrees as measured by phasing analysis and were oriented t oward both the major and the minor grooves at the center of the AP-1 s ite. The DNA bends induced by the various heterodimeric complexes sugg ested that each component of the complex induced an independent DNA be nd as previously shown for Fos and Jun. The Fos-related proteins Fra1 and Fra2 bent DNA in the same orientation as Fos but induced smaller D NA bend angles. ATF2 also bent DNA toward the minor groove in heterodi mers formed with Fos, Fra2, and Jun. CREB and ATF1, which favor bindin g to the CRE site, did not induce significant DNA bending. Zta, which is a divergent member of the bZIP family, bent DNA toward the major gr oove. A variety of DNA structures can therefore be induced at the AP-1 site through combinatorial interactions between different bZIP family proteins. This diversity of DNA structures may contribute to regulato ry specificity among the plethora of proteins that can bind to the AP- 1 site.