Transcriptional corepressor. Acts as dominant repressor towards other family members. Inhibits NF-kappa-B-regulated gene expression. May be required for the initiation and maintenance of the differentiated state. Essential for the transcriptional repressor activity of SIX3 during retina and lens development. Homooligomer and heterooligomer with other family members. Binds TCF7 (By similarity). Binds the NF-kappa-B subunit RELA. Interacts with PHF12. Interacts (via Q domain) with SIX3. Interacts with SIX6. Found predominantly in muscle, heart and Placenta. In fetal tissues, abundantly expressed in the heart, lung, kidney, brain and liver. Lacks the C-terminal WD repeats. Ubiquitinated by XIAP/BIRC4. Belongs to the WD repeat Groucho/TLE family. Truncated N-terminus.