KAP-1 (Alternative names: TIF1b or TRIM28) is one member of transcriptional intermediary factors, which acts as a scaffold in many transcription regulation complexes. The N-terminal RBCC domain of KAP-1 can interact with KRAB-ZFPs, MDM2, MM1, C/EBPb, etc. KAP-1’s C-terminal PHD and Bromodomain is two integrated transcriptional repression domains, which interact with SETDB1, Mi-2a and other proteins to form complexes with histone deacetylase or methyltransferase activity. In addition, KAP-1 can interact with HP1s (heterochromatin protein 1) and then bind to histones via its HP1BD which is a small segment in the central region of KAP-1. It is indicated by many researches that KAP-1, a scaffold protein in transcription regulation, mainly acts as a corepressor in many repression complexes. Meanwhile, it also acts as a coactivator sometimes. It is reported that KAP-1 related transcription regulation complexes exert functions essen-tial for spermiogenesis and early embryo development. This regulation is one pattern of epigenetic regulations.