Functions as transcription repressor, probably via its interaction with histone deacetylase complexes. Involved in the functional recruitment of the class 1 Sin3-histone deacetylase complex (HDAC) to the nucleolus. Binds DNA, apparently without sequence-specificity, and bends bound double-stranded DNA. Binds phosphoinositol phosphates (phosphoinositol 3-phosphate, phosphoinositol 4-phosphate and phosphoinositol 5-phosphate) via the same basic sequence motif that mediates DNA binding and nuclear import. Interacts with components of the histone deacetylase complex sin3a, hdac1 and hdac2. Binds histones and nucleosomes. The zinc-finger domain mediates direct interaction with DNA and phosphoinositol phosphates (phosphoinositol 3-phosphate, phosphoinositol 4-phosphate and phosphoinositol 5-phosphate). In vitro oxydation causes reversible disulfide bond formation between Cys residues in the zinc-finger domain and reversible loss of zinc ion binding. Belongs to the SAP30 family.