Functional differences between the human ATP-dependent nucleosome remodeling proteins BRG1 and SNF2H.

ATP-dependent nucleosome remodeling complexes can be grouped into several classes that may differ in their biochemical remodeling activities and biological roles. Although there are a number of biochemical studies of each class of remodeler, there are very little data directly comparing the biochemical activities of remodelers from different classes. We have purified two ATP-hydrolyzing proteins, SNF2H and BRG1, which are members of complexes from two different classes of remodelers. Consistent with previous reports, these two homogeneous proteins can perform remodeling functions. We show significant functional differences between SNF2H and BRG1 in vitro; although both SNF2H and BRG1 hydrolyze ATP and remodel linear arrays of nucleosomes, only BRG1 can remodel mononucleosomes. Also, only BRG1 can alter the topology of nucleosomal plasmids. We propose that these functional differences reflect significant mechanistic differences between the two remodeler classes that will impact their biological roles.