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KAP1 regulates ERVs in differentiated human cells and contributes to innate immune control

ABSTRACT: Endogenous retroviruses (ERVs) have accumulated in vertebrate genomes and contribute to the complexity of gene regulation. KAP1 represses ERVs during development by its recruitment to their repetitive sequences through KRAB-zinc finger proteins (KZNFs), but little is known about the regulation of ERVs in differentiated cells. We observed that KAP1 repression of HERVK14C was conserved in differentiated human cells and performed KAP1 knockout to obtain an overview of KAP1 function. Our results show that KAP1 represses ERVs (including HERV-T and HERV-S) and ZNFs, both of which overlap with KAP1 binding sites and H3K9me3 in multiple cell types. Furthermore, this pathway is functionally conserved in primary peripheral blood mononuclear cells. Cytosine methylation that acts on KAP1-regulated loci is necessary to prevent an interferon response, and KAP1-depletion leads to activation of some interferon-stimulated genes. Finally, loss of KAP1 leads to a decrease in H3K9me3 enrichment at ERVs and ZNFs and an RNA-sensing response mediated through MAVS signaling. These data indicate that the KAP1-KZNF pathway contributes to genome stability and innate immune control in differentiated human cells.

ORGANISM(S): Homo sapiens

PROVIDER: GSE114998 | GEO | 2018/07/15

REPOSITORIES: GEO

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Project description:Only a small percentage of human transcription factors (e.g. those associated with a specific differentiation program) are expressed in a given cell type. Thus, cell fate is mainly determined by cell type-specific silencing of transcription factors that drive different cellular lineages. Several histone modifications have been associated with gene silencing, including H3K27me3 and H3K9me3. We have previously shown that the two largest classes of mammalian transcription factors are marked by distinct histone modifications; homeobox genes are marked by H3K27me3 and zinc finger genes are marked by H3K9me3. Several histone methyltransferases (e.g. G9a and SETDB1) may be involved in mediating the H3K9me3 silencing mark. We have used ChIP-chip (GSE24480) and ChIP-seq to demonstrate that SETDB1, but not G9a, is associated with regions of the genome enriched for H3K9me3. A current model is that SETDB1 is recruited to specific genomic locations via interaction with the corepressor TRIM28 (KAP1), which is in turn recruited to the genome via interaction with zinc finger transcription factors that contain a Kruppel-associated box (KRAB) domain. However, specific KRAB-ZNFs that recruit TRIM28 (KAP1) and SETDB1 to the genome have not been identified. We now show that ZNF274 (a KRAB-ZNF that contains 5 C2H2 zinc finger domains), can interact with KAP1 in vitro and, using ChIP-seq, we show that ZNF274 binding sites co-localize with SETDB1, KAP1, and H3K9me3 at the 3’ ends of zinc finger genes. Knockdown of ZNF274 with siRNAs reduced the levels of KAP1 and SETDB1 recruitment to the binding sites. These studies provide the first identification of a KRAB domain-containing ZNFs that is involved in recruitment of the KAP1 and SETDB1 to the human genome. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf 7 total ChIP-seq datasets; 4 ZNF274 datasets done in duplicate from 4 different cell lines; 1 KAP1 duplicate dataset done in duplicate from K562 cells; 1 SetDB1 duplicate dataset from K562 cells; 1 H3K9me3 duplicate dataset from K562 cells

Project description:KAP1 is overexpressed in breast cancer. To determine KAP1 regulated genes, we performed microarray analysis of gene expression in KAP1 depleted breast cancer cells MDA-MB-231LN. The transcriptional regulator TRIM28/KAP1 plays an important role in development, stem cell self-renewal, chromatin organization and the DNA damage response. KAP1 is an essential co-repressor for KRAB zinc finger proteins (KRAB-ZNFs). Though KRAB-ZNFs represent the largest family of human transcription factors, their biological functions are largely unknown. Using the conserved zinc fingers linker region (ZnFL) as antigen, we have developed a ZnFL antibody that recognizes multiple KRAB-ZNFs. We showed that KAP1 and many KRAB-ZNFs were overexpressed in human breast cancers and breast cancer cell lines. In addition, an active SUMOylated form of KAP1 was markedly increased in breast cancer cells. Furthermore, KAP1 depletion in breast cancer cell lines reduced cell proliferation and inhibited tumor growth and metastasis of tumor xenografts. Conversely, KAP1 overexpression stimulated cell proliferation and tumor growth. KAP1 knockdown led to down-regulation of genes previously linked to tumor progression and metastasis, including PTGS2/COX2, EREG, CD44, MMP1 and MMP2. Interestingly, KAP1 depletion or genomic deletion led to dramatic down-regulation of multiple KRAB-ZNF proteins due in part to their increased degradation. KAP1-dependent stabilization of KRAB-ZNFs required a direct KRAB-ZNF-KAP1 interaction. These results establish KAP1 as a positive regulator of multiple KRAB-ZNFs and an important factor in the development of breast cancer. 7 total samples were analyzed. Stable sublines of MDA-MB-231LN cells expressing control non-targeting shRNA (Scr, 3 biological replicates) and two different shRNAs against KAP1 (KAP1-3, 2 biological replicates and KAP1-4, 2 biological replicates) from doxycycline-inducible pTRIPZ vector were cultured in the presence of 0.5 ug/ml doxycycline for 7 days to induce shRNA expression. Cells were lysed and total RNA was isolated using mirVana miRNA isolation kit (Ambion) in the WVU Genomics Core Facility.

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KAP1 regulates ERVs in differentiated human cells and contributes to innate immune control

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