Transcriptional coregulator which can act as both a transcriptional corepressor and coactivator. As a part of the histone-deacetylase multiprotein complex (NuRD), regulates transcription of its targets by modifying the acetylation status of the target chromatin and cofactor accessibility to the target DNA. In conjunction with other components of NuRD, acts as a transcriptional corepressor of BRCA1, ESR1, TFF1 and CDKN1A. Acts as a transcriptional coactivator of BCAS3, PAX5 and SUMO2, independent of the NuRD complex. Stimulates the expression of WNT1 by inhibiting the expression of its transcriptional corepressor SIX3. Regulates p53-dependent and -independent DNA repair processes following genotoxic stress. Regulates the stability and function of p53/TP53 by inhibiting its ubiquitination by COP1 and MDM2 thereby regulating the p53-dependent DNA repair. Plays an important role in tumorigenesis, tumor invasion, and metastasis. Plays a role in the regulation of the circadian clock and is essential for the generation and maintenance of circadian rhythms under constant light and for normal entrainment of behavior to light-dark (LD) cycles. Positively regulates the CLOCK-ARNTL/BMAL1 heterodimer mediated transcriptional activation of its own transcription and the transcription of CRY1. Regulates deacetylation of ARNTL/BMAL1 by regulating SIRT1 expression, resulting in derepressing CRY1-mediated transcription repression. With Tfcp2l1, promotes establishment and maintenance of pluripotency in embryonic stem cells (ESCs) and inhibits endoderm differentiation (PubMed:28982712). Component of the nucleosome-remodeling and histone-deacetylase multiprotein complex (NuRD). Interacts with HDAC1 and ITGB3BP/CENPR (By similarity). Binds to CSNK1G2 in the cytoplasm (PubMed:15077195). Interacts with NACC2. Interacts with EP300, TFAP2C, IFI16, TPR, UBE2I/UBC9, PIAS1, PIAS3, PIAS4, MDM2, COP1, SUMO1, SUMO2, SENP1 and SENP2 (By similarity). Interacts with ARNTL/BMAL1 and CLOCK (PubMed:24089055). Interacts with p53/TP53 (PubMed:19837670). Interacts with HDAC2 (By similarity). Interacts with SIX3; facilitates the binding of SIX3 to the core DNA motif of SIX3 promoter (PubMed:17666527). Interacts with TFCP2L1; which is indispensable for TFCP2L1-mediated self-renewal-promoting effect and endoderm-inhibiting action (PubMed:28982712). Interacts with PWWP2A and PWWP2B (PubMed:30228260, PubMed:34180153). Associated with microtubules. Primarily localized in the cytoplasm in embryonic tissues. Localization at the nuclear envelope is TPR-dependent. Widely expressed but not in skeletal muscle. Highly expressed in the brain, liver, kidney and cardiac muscle and in mammary tumors. Expressed at high levels in embryonic nerve tissues, such as the brain, eyes, and spinal cord. Phosphorylation by CSNK1G2/CK1 triggered by estrogen enhances corepression of estrogen receptor (ER). Acetylation is essential for its transcriptional coactivator activity. Sumoylation positively regulates its transcriptional corepressor activity but does not affect the protein stability. Sumoylated preferentially by SUMO2 or SUMO3 than SUMO1. Sumoylation is enhanced by PIAS1/3/4 and preferentially sumoylated by SUMO2 in the presence of PIAS1/3/4. Desumoylated by SENP1 (By similarity). Ubiquitinated by COP1, which leads to proteasomal degradation. Mice exhibit a disruption of the free-running period of circadian rhythms under constant light and normal entrainment of behavior to light-dark (LD) cycles. Was originally thought to play a role in inflammatory responses both as a target and as a component of the NF-kappa-B signaling, to interact with the HDAC2, and be induced by lipopolysaccharide (LPS) (PubMed:20519513). However, this work was later retracted (PubMed:28314777). Nevertheless, the interaction with HDAC2 has been demonstrated by several publications in the human ortholog. Truncated N-terminus.