Transcriptional repressor. It plays an important role in the specification and differentiation of lung epithelium. Can act with CTBP1 to synergistically repress transcription but CTPBP1 is not essential. Essential transcriptional regulator of B-cell development. Forms homodimers and heterodimers with FOXP2 and FOXP4. Dimerization is required for DNA-binding. Interacts with CTBP1. 5 isoforms of the human protein are produced by alternative splicing. Note: This description may include information from UniProtKB.