KAP1 facilitates the establishment of viral latency in certain cell types for Human Cytomegalovirus (HCMV) and other endogenous retroviruses
.  KAP1 acts as a transcriptional corepressor of the viral genome.  The protein binds to the histones of the viral chromatin and then recruits Mi2α and SETB1.  SETB1 is a histone methyltransferase that recruits HP1, thus inducing heterochromatin formation.  This heterochromatin formation prevents the transcription of the viral genome.  mTOR has been implicated in the phosphorylation of KAP1 resulting in a switch from latency to the lytic cycle.