GSE162571
Genetic deletion of ZNF91 in human embryonic stem cells leads to ectopic activation of SVAs and collective upregulation of KRAB zinc finger gene clusters
Transposable element (TE) invasions have shaped vertebrate genomes over the course of evolution. They have contributed an extra layer of species-specific gene regulation by providing novel transcription factor binding sites. In humans, SVA elements are one of three still active TE families, and approximately 2800 SVA insertions exist in the human genome, half of which are human-specific. TEs are often silenced by KRAB zinc finger (KZNF) proteins recruiting co-repressor proteins that establish a repressive chromatin state. A number of KZNFs have been reported to bind SVAs, but their individual contribution to repressing SVAs and their roles in suppressing SVA-mediated gene-regulatory effects remains elusive. We analyzed the genome-wide binding profile for ZNF91 in human cells and found that ZNF91 interacts with the VNTR region of SVAs. Through CRISPR-Cas9 mediated deletion of ZNF91 in human embryonic stem cells we established that loss of ZNF91 results in increased transcriptional activity of SVAs. In contrast, SVA activation was not observed upon genetic deletion of the ZNF611 gene encoding another strong SVA-interactor. Epigenetic profiling confirmed the loss of SVA repression in the absence of ZNF91 and revealed that mainly evolutionary young SVAs gain gene activation-associated epigenetic modifications. Genes close to activated SVAs showed a mild upregulation, indicating SVAs adopt properties of cis-regulatory elements in the absence of repression. Intriguingly, genome-wide de-repression of SVAs elicited the communal upregulation of KZNFs that reside in KZNF clusters. This phenomenon may provide new insights into the potential mechanisms utilized by the host genome to sense and counteract TE invasions. Overall design: Identification of ZNF91 binding sites in HEK293 cells using ZNF91-GFP overexpression followed by ChIP-seq. RNA seq and ChIP seq analysis of CRISPR/Cas9 ZNF91 wild type and knockout human embryonic stem cell lines