Transcription factor that binds to sequence with multiple copies of 5'-TTC[CG]G-3' present in its own promoter and that of the HNRPA2B1 gene. Down-regulates transcription of these genes. Binds to the retinoic acid response element (RARE) 5'-AGGGTTCACCGAAAGTTCA-3'. Activates the proenkephalin gene independently of promoter binding, probably through protein-protein interaction (By similarity). Regulates epithelial cell proliferation and side-branching in the mammary gland. Required for neural tube closure and skeletal patterning. Controls the expression of peripheral tissue antigens in pancreatic lymph nodes. Isoform 1 displays greater transcriptional activity than isoform 2. Isoform 2 may inhibit transcriptional activity of isoform 1 by interacting with it and retaining it in the cytoplasm. Transcriptional activator of EIF4G3 (By similarity). May also involved in behavior (PubMed:24726472). Homodimer (By similarity). Isoform 1 and isoform 2 may form a heterodimer. May interact with the corepressors NCOR1 and NCRO2 (By similarity). Identified in a complex with XRCC5 and XRCC6. Interacts (via the SAND domain) with the DNA-PK complex subunit XRCC6; the interaction is direct with XRCC6 and may be inhibited by DNA-binding (By similarity). Interacts with LMO4; LMO4 blocks export from nucleus. Interacts with LMO2 and CLIM2. Displays some nuclear localization when expressed with isoform 1, suggesting that it may heterodimerize with isoform 1 and shuttle to the nucleus using the nuclear localization signal of isoform 1. Ubiquitously expressed during embryogenesis, with higher expression in regions of the central nervous system, dorsal root ganglia, submandibular gland, epidermis and breast. In 12-week-old NOD mice, expression of isoform 2 is sevenfold higher in lymph node stromal elements than in T-cells and tenfold higher than in B-cells. Expressed at all stages of mammary gland development with slightly higher levels observed during pregnancy and lactation. At 4 weeks, expression levels of isoform 1 and isoform 2 do not differ in pancreatic lymph nodes of nonobese diabetic (NOD) mice compared to NOD.B10 mice which do not develop diabetes. However, at 12 weeks, expression of isoform 1 is down-regulated while expression of isoform 2 is up-regulated in NOD mice but not in NOD.B10. There is no difference in expression levels at 12 weeks in spleen. May be phosphorylated by DNA-PK complex in a DNA independent manner (in vitro). Exencephaly and skeletal abnormalities in the rib cage and cervical vertebrae but no presphenoid bone or cranial nerve defects. DEAF1 homozygous mice neonates die 100% of the time and DEAF1 heterozygous mice survived in a 2:1 ratio.