The Snf2 Homolog Fun30 Acts as a Homodimeric ATP-dependent Chromatin-remodeling Enzyme*

The Saccharomyces cerevisiae Fun30 (Function unknown now 30) protein shares homology with an extended family of Snf2-related ATPases. Here we report the purification of Fun30 principally as a homodimer with a molecular mass of about 250 kDa. Biochemical characterization of this complex reveals that it has ATPase activity stimulated by both DNA and chromatin. Consistent with this, it also binds to both DNA and chromatin. The Fun30 complex also exhibits activity in ATP-dependent chromatin remodeling assays. Interestingly, its activity in histone dimer exchange is high relative to the ability to reposition nucleosomes. Fun30 also possesses a weakly conserved CUE motif suggesting that it may interact specifically with ubiquitinylated proteins. However, in vitro Fun30 was found to have no specificity in its interaction with ubiquitinylated histones.