TIF1β, for transcriptional intermediary factor 1-beta, also designated KAP1(for KRAB-associated protein 1), TF1β and TRIM28 (for tripartif motif-containing 28), is a member of the tripartif motif family characterized by three zinc-binding domains, a RING finger, B-boxes and a coiled-coil domain. Like TIF1α, TIF1β contains both a Cys/His PHD (plant homeodomain) finger and bromodomain that form a cooperative unit required for transcriptional repression. TIF1β mediates transcriptional control by interaction with the Kruppel-associated box (KRAB) repression domain found in many transcription factors and by binding DNA through its zinc finger. The human TIF1β gene maps to human chromosome 19q13.4 and encodes an 835 amino acid nuclear protein.
