Required for proper positioning of nucleosomes at heterochromatic loci and for transcriptional gene silencing (TGS) function of the Snf2/Hdac-containing repressor complex (SHREC). Interacts with clr3. Associates with major heterochromatin, centromeres, sub-telomeres, rDNA and the mat locus. Belongs to the SNF2/RAD54 helicase family.