Key regulator of both differentiation and survival of T-lymphocytes during thymocyte development in mammals (PubMed:12717433). Essential in controlling the responsiveness of hematopoietic stem cells to chemotactic signals by modulating the expression of receptors CCR7 and CCR9, which direct the movement of progenitor cells from the bone marrow to the thymus (By similarity). Is a regulator of IL2 promoter and enhances IL2 expression in activated CD4(+) T-lymphocytes (PubMed:16809611). Tumor-suppressor protein involved in T-cell lymphomas. May function on the P53-signaling pathway. Repress transcription through direct, TFCOUP2-independent binding to a GC-rich response element. Interacts with TFCOUP1, SIRT1, ARP1 and EAR2 (PubMed:10744719, PubMed:12930829). Interacts with EP300; the interaction is detected in activated T-lymphocytes, but not under resting conditions (By similarity). Expressed in brain and thymus. Expressed in splenic CD4(+) T-lymphocytes (PubMed:16809611). Highly expressed in the developing embryo. Sumoylated with SUMO1. May be due to exon skipping. May be due to exon skipping.