Functions as transcription repressor, probably via its interaction with histone deacetylase complexes (PubMed:22821512). Required for normal expression of numerous target genes (PubMed:22821512). 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 (By similarity). Interacts with components of the histone deacetylase complex sin3a, hdac1 and hdac2. Binds histones and nucleosomes. Detected in embryos at 2dpf (at protein level). Widely expressed during embryogenesis and in adults. 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. Morpholino knockdown causes defects in embryonic heart morphogenesis and pericardiac edema, with defects in heart function that are visible already at 3 dpf. In addition, erythrocytes appear pale due to decreased hemoglobin content. Belongs to the SAP30 family.