Zfp819, a novel KRAB-zinc finger protein, interacts with KAP1 and functions in genomic integrity maintenance of mouse embryonic stem cells.

Pluripotency is maintained by both known and unknown transcriptional regulatory networks. In the present study, we have identified Zfp819, a KRAB-zinc finger protein, as a novel pluripotency-related factor and characterized its role in pluripotent stem cells. We show that Zfp819 is expressed highly in various types of pluripotent stem cells but not in their differentiated counterparts. We identified the presence of non-canonical nuclear localization signals in particular zinc finger motifs and identified them as responsible for the nuclear localization of Zfp819. Analysis of the Zfp819 promoter region revealed the presence of a transcriptionally active chromatin signature. Moreover, we confirmed the binding of pluripotency-related factors, Oct4, Sox2, and Nanog to the distal promoter region of Zfp819, indicating that the expression of this gene is regulated by a pluripotency transcription factor network. We found that the expression of endogenous retroviral elements (ERVs) such as Intracisternal A Particle (IAP) retrotransposons, Long Interspersed Nuclear Elements (LINE1), and Short Interspersed Nuclear Elements (SINE B1) is significantly upregulated in Zfp819-knockdown (Zfp819_KD) cells. In line with the activation of ERVs, we observed the occurrence of spontaneous DNA damage in Zfp819_KD cells. Furthermore, we tested whether Zfp819 can interact with KAP1, a KRAB-associated protein with a transcriptional repression function, and found the interaction between these two proteins in both in vitro and in vivo experiments. The challenging of Zfp819_KD cells with DNA damaging agent revealed that these cells are inefficient in repairing the damaged DNA, as cells showed presence of γH2A.X foci for a prolonged time. Collectively, our study identified Zfp819 as a novel pluripotency-related factor and unveiled its function in genomic integrity maintenance mechanisms of mouse embryonic stem cells.