Functions as a transcriptional repressor. Seems to function as a transcriptional corepressor in neuronal cells through recruitment of HDAC3 and HDAC4. Contributes to tumor progression, and tumor cell proliferation and survival. This may be mediated at least in part through repressing transcriptional activity of GADD45GIP1. Required for recruiting the proteasome from the nucleus to the cytoplasm and dendritic spines. Involved in the acute behavioral and neurological responses to cocaine and amphetamines. Homooligomer; mediated by the BTB domain. Interacts with HDAC3 and HDAC4. Interacts (via BTB domain) with CUL3, PSMD7 AND RCOR1 (By similarity). Distribution in the cytoplasm is dependent on phosphorylation. Ubiquitously expressed with higher expression in the brain, kidney and liver, and at lower levels in heart, lung and testes. Mice are viable with no obvious developmental or physiological impairments. In addition, they do not display alterations in chronic responses to cocaine and amphetamine administration, but do however display significantly diminished acute behavioral and neurochemical responses to these drugs.