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Individual retrotransposon integrants are differentially controlled by KZFP/KAP1-dependent histone methylation, DNA methylation and TET-mediated hydroxymethylation in naïve embryonic stem cells

ABSTRACT: The KZFP/KAP1 (KRAB zinc finger proteins/KRAB-associated protein 1) system plays a central role in the silencing of transposable elements (TEs) and the maintenance of parent-of-origin DNA methylation at imprinting control regions (ICRs) during the wave of genome-wide reprogramming that precedes implantation. In naïve murine embryonic stem cells (mESCs), the genome is maintained highly hypomethylated by a combination of active demethylation (operated by TET proteins) and lack of de novo methylation; in these cells, KAP1 is tethered by sequence-specific KZFPs to ICRs and TEs where it recruits histone and DNA methyltransferases to impose heterochromatin formation and DNA methylation. Here, upon removing either KAP1 or the cognate KZFP, we observed rapid TET-dependent accumulation of 5hmC at both ICRs and TEs. In absence of the KZFP/KAP1 complex, ICRs lost heterochromatic histone marks and underwent both active and passive DNA demethylation. Using RNA-seq, we further compared the expression profiles of TEs upon Kap1 removal in wild type, Dnmt and Tet triple knockout mESCs. We found that KAP1 represents the main effector of TEs repression in all three settings, yet we could additionally identify specific groups of TEs also controlled by DNA methylation. Furthermore, activation upon Kap1 removal in the absence of TET proteins could be either blunted or increased depending on TE subsets, indicating a complex interplay between heterochomatin and active demethylation in regulating the expression of the endovirome.

ORGANISM(S): Mus musculus

PROVIDER: GSE95720 | GEO | 2018/02/28

REPOSITORIES: GEO

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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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Individual retrotransposon integrants are differentially controlled by KZFP/KAP1-dependent histone methylation, DNA methylation and TET-mediated hydroxymethylation in naïve embryonic stem cells

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