Regulatory protein which represses transcription and augments histone deacetylase activity of HDAC1. May have a potential role in tumor suppressor pathways through regulation of apoptosis. May function in the assembly and/or enzymatic activity of the mSin3A corepressor complex or in mediating interactions between the complex and other regulatory complexes. Homodimer. Component of the SIN3 histone deacetylase (HDAC) corepressor complex. Interacts with SIN3A. Interaction with SIN3B enhances the interaction between SIN3B and HDAC1 to form a complex (By similarity). Interacts with HCFC1. Component of a mSin3A corepressor complex that contains SIN3A, SAP130, SUDS3/SAP45, ARID4B/SAP180, HDAC1 and HDAC2. Interacts with USP17L2; the interaction is direct. Interacts with FOXK2 (PubMed:25805136). Expressed in various cancer cell ines. The C-terminus is involved in transcriptional repression by HDAC-independent mechanisms. Polyubiquitinated. 'Lys-63'-polyubiquitinated SUDS3 positively regulates histone deacetylation. Regulated through deubiquitination by USP17L2/USP17 that cleaves 'Lys-63'-linked ubiquitin chains. Belongs to the SDS3 family. Truncated N-terminus. Extended N-terminus.