DNA-BINDING PROPERTIES OF THE YEAST SWI SNF COMPLEX/

The SWI/SNF complex is required for the enhancement of transcription b y many transcriptional activators in yeast(1,2) Genetic and biochemica l studies indicate that the complex facilitates activator function by antagonizing chromatin-mediated transcriptional repression(3-6). The a bsence of known DNA-binding motifs in several SWI/SNF subunits and the failure to identify SWI/SNF-dependent DNA-binding activities in crude yeast extracts have led to the belief that the complex does not bind DNA(7,8). Here we show that the SWI/SNF complex has a high affinity fo r DNA and that its DNA-binding properties are similar to those of prot eins containing HMG-box domains(9). The complex interacts with the min or groove of the DNA helix, binds synthetic four-way junction DNA, and introduces positive supercoils into relaxed plasmid DNA. These proper ties are likely to be important in the remodelling of chromatin struct ure by the SWI/SNF complex.