KAP1 is a well-known transcriptional corepressor of KRAB-ZFPs. The N-terminus of KAP1
contains a tripartite motif composed of a Ring finger, two B-box zinc fingers and a coiled-coil (RBCC)
domain; this motif binds the KRAB repression module as a homotrimer. It has been shown that
transcriptional repression mediated by KRAB-ZNFs depends on KAP1 as well as on its interacting
partners [1,2]. Indeed, the C-terminus tandem PHD and the bromodomain of KAP1 act as scaffold
domains recruiting histone deacetylases, histone methylases and other chromatin modifiers to promoters of
target genes. Furthermore, the central region of KAP1 includes the binding domain of heterochromatin
protein 1 (HP1), involved in heterochromatin packaging. In this way, KAP1 coordinates the assembly
of components required for gene silencing by forming a facultative heterochromatin environment [3,4].
Moreover, KAP1 is subjected to several post-translational modifications, including SUMOylation and
phosphorylation [5,6]. These modifications, required for the repressive activity and for the recruitment
of histone deacetylase complexes and HP1, are crucial to properly regulate the expression of KAP1-target
genes in response to different extracellular stimuli [7–9].