Identification of SWI center dot SNF complex subunit BAF60a as a determinant of the transactivation potential of Fos/Jun dimers

Fos family proteins form stable heterodimers with Jun family proteins, and each heterodimer shows distinctive transactivating potential for regulating cellular growth, differentiation, and development via AP-1 binding sites. However, the molecular mechanism underlying dimer specificity and the molec ules that facilitate transactivation remain undefined. Here, we show that B AF60a, a subunit of the SWI.SNF chromatin remodeling complex, is a determin ant of the transactivation potential of Fos/Jun dimers. BAF60a binds to a s pecific subset of Fos/Jun heterodimers using two different interfaces for c -Fos and c-Jun, respectively. Only when the functional SWI.SNF complex is p resent, can c-Fos/c-Jun (high affinity to BAF60a) but not Fra-2/JunD (no af finity to BAF60a) induce the endogenous AP-1-regulated genes such as collag enase and c-met, These results indicate that a specific subset of Fos/Jun d imers recruits SWI.SNF complex via BAF60a to initiate transcription.