KAP-1, also known as KRAB-associated protein 1 or TIF1β (transcriptional intermediary factor 1β), is a multifunctional protein involved in a variety of cellular processes, including transcriptional regulation, DNA repair, and maintenance of genomic integrity. KAP-1 functions as a transcriptional corepressor by interacting with KRAB-ZNFs, which recruit it to specific genomic loci. Once bound, KAP-1 can influence the epigenetic state of the targeted DNA, leading to transcriptional repression through the recruitment of chromatin-modifying enzymes such as histone deacetylases (HDACs) and histone methyltransferases (HMTs) like SETDB1. This results in the formation of repressive chromatin marks, such as H3K9me3, which contribute to the establishment of a heterochromatic environment. In addition to its role in transcriptional regulation, KAP-1 has been implicated in the maintenance of pluripotency in stem cells and is required for terminal differentiation of mouse embryonic stem cells. It is also associated with promoting and inhibiting differentiation of various adult cell types, suggesting a complex role in cellular development and differentiation.