Zinc finger protein 809 (ZFP809) is a member of the kruppel-associated boxcontaining ZFP (KRAB-ZFP) family. It supresses the expression of Moloney murine leukemia virus (MoMLV) via sequence-specific binding to the primer binding site (PBS) located downstream of the MoMLV-long terminal repeat (LTR) and induces epigenetic modifications at the LTR, such as repressive histone modifications and de novo DNA methylation. Recent studies have demonstrated the features of diverse functional domains of ZFP809, which has a KRAB domain and seven zinc fingers. We previously demonstrated that the KRAB domain is essential for nuclear localization, gene silencing, and binding to the MLV-PBS in conjunction with the accessory roles of a subset of zinc fingers. Individual zinc fingers are known to contribute to binding to the MLV-PBS and stable protein expression. Furthermore, the mechanisms underlying the high expression of ZFP809 in immature cells have yet to be fully elucidated. Recent studies have indicated that ZFP809 is stably expressed in immature cells, such as embryonic stem cells (ESCs), as ESCs have higher expression of KRAB-associated protein 1 (KAP1) than mature mouse embryonic fibroblast cells. Here we discuss the ZFP809/KAP1 complex, functional domains of ZFP809, and expression pattern of ZFP809 in immature cells.
Yu Ichida, Yuko Utsunomiya and Masafumi Onodera
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