Transcriptional regulator with bimodal DNA-binding specificity. Binds with a higher affinity to methylated CpG dinucleotides in the consensus sequence 5'-CGCG-3' but can also bind to E-box elements (5'-CACGTG-3'). Can also bind specifically to a single methyl-CpG pair. Represses transcription in a methyl-CpG-dependent manner. Plays an important role in regulating DNA-replication and common fragile sites (CFS) stability in a RBBP6- and MCM10-dependent manner; represses expression of MCM10 which plays an important role in DNA-replication (By similarity). Acts as a transcriptional activator. May be involved in the differentiation and/or survival of late postmitotic neurons (PubMed:15713629). Interacts with CBFA2T3, ZBTB4 and RBBP6. Localizes to chromocenters. Widely expressed throughout the adult brain where it is found mainly in neurons. Also expressed in the adrenal medulla. Not detected in non-neural tissues including heart, spleen, liver and muscle. In the embryo, expressed in the developing brain and spinal cord but not in the migratory neural crest. Also expressed in the limbs, transiently in somites, and in the embryonic liver. In the embryonic neural tube, expression is restricted to late postmitotic neurons. Expressed in embryo and adult. Embryonic expression is detected from E12. The BTB domain is not required for activation of transcription or self-association. Ubiquitinated by RBBP6; leading to its degradation by the proteasome.