Project description:We report a retrotransposon-specific loss of CpG methylation in chromosome 4 KRAB-ZFP cluster (Chr4-cl) KO ES cells that are cultivated in conditions that induce DNA hypomethylation. The retrotransposon groups with the strongest DNA methylation loss are the main targets of the KRAB-ZFPs within the deleted gene cluster indicating that these KRAB-ZFPs prevent complete DNA demethylation at retrotransposons during global DNA demethylation.
Project description:We have shown that many mouse KRAB-ZFPs target retrotransposons which are generally marked by H3K9me3 and KAP1 in ES cells. To test whether these KRAB-ZFPs are require to establish and maintain repressive chromatin marks at these elements, we performed ChIP-seq with antibodies against KAP1 (2 KRAB-ZFP cluster KOs) and H3K9me3 (5 KRAB-ZFP cluster KOs). We show that KRAB-ZFP targeted retrotransposons show reduced KAP1 binding and H3K9me3 in these KO ES cells. Furthermore, we performed ChIP-seq with antibodies against histone modifications typical for promoters and enhancers in Chr4-cl KO ES cells and testis. We show that, in ES cells, ETn retrotransposons gain signatures of active enhancers which acts on earby gene expression. In testis, a handful of different retrotransposons gain enhancer marks, although to a lesser degree. In conclusion, our data shows that KRAB-ZFPs are required to maintain H3K9me3 at retrotransposons in ES cells and to prevent some retrotransposons of becoming enhancers that affect gene expression patterns.
Project description:Mammalian genomes encode several hundred Krüppel-associated box zinc finger proteins (KRAB-ZFPs) that bind DNA in a sequence-specific manner through tandem arrays of C2H2-type zinc fingers and repress transcription via KRAB-dependent recruitment of the silencing cofactor KAP1. The KRAB-ZFP family rapidly amplified and diversified in mammals by segmental gene duplications, mutations, and zinc finger rearrangements likely in response to continued transposable element invasions, but the biological functions and in vivo requirement of these proteins has gone largely unexplored. We determined the genomic binding sites of 61 murine KRAB-ZFPs and genetically deleted five large KRAB-ZFP gene clusters encoding more than 100 of the approximately 360 mouse KRAB-ZFPs. We demonstrate that most KRAB-ZFPs bind to specific retrotransposon families and that many of these retrotransposons are transcriptionally activated in KRAB-ZFP cluster KO ESCs, licensing retrotransposon-derived enhancers to activate nearby genes.
Project description:Genetic deletion of a large KRAB-ZFP gene cluster on chromosome 4 (Chr4-cl) leads to transcriptional reactivation of retrotransposons (mainly ETn elements) in ES cells. We therefore wanted to test whether ETn elements retrotranspose in Chr4-cl KO mice at higher frequency. For this we purified genomic DNA from WT and KO mice, enriched gDNA libraries using ETn capture probes and sequenced those libraries as paire-end reads. These reads were then used to identify novel ETn insertions that are not annotated in the reference genome or present in the germ line of their progenitors.
Project description:The tetrapod-restricted KRAB-containing zinc finger proteins (KRAB-ZFPs) are essential early embryonic controllers of transposable elements (TEs), which they repress via their cofactor KAP1 and associated effectors through histone and DNA methylation, a process thought to result in irreversible silencing. Using a target-centered functional screen, we matched several murine TEs with their cognate KRAB-ZFP. This revealed an unexpected level of granularity in their interactions, with KRAB-ZFPs recognizing TEs from more than one subfamily, TEs recruiting more than one KRAB-ZFP, and spatially and temporally differential KRAB-ZFP-mediated regulation of TEs and nearby genes. Most importantly, we discovered that the KRAB/KAP1 system controls TEs in adult tissues, in cell culture and in vivo, where they partner up to regulate the expression of cellular genes. Therefore, TEs and KRAB-ZFPs establish widely active transcription networks that regulate not only development but probably also many physiological events. Given the high degree of species-specificity of both TEs and KRAB-ZFPs, these results have important implications for studying and understanding the biology of higher vertebrates, including humans. Analysis of transcriptional profiles of KAP1 or ZFP932/Gm15446 KO cells or tissues, and ZFP932 and Gm15446 ChIPseq in murine ES and C2C12 cells.
Project description:The tetrapod-restricted KRAB-containing zinc finger proteins (KRAB-ZFPs) are essential early embryonic controllers of transposable elements (TEs), which they repress via their cofactor KAP1 and associated effectors through histone and DNA methylation, a process thought to result in irreversible silencing. Using a target-centered functional screen, we matched several murine TEs with their cognate KRAB-ZFP. This revealed an unexpected level of granularity in their interactions, with KRAB-ZFPs recognizing TEs from more than one subfamily, TEs recruiting more than one KRAB-ZFP, and spatially and temporally differential KRAB-ZFP-mediated regulation of TEs and nearby genes. Most importantly, we discovered that the KRAB/KAP1 system controls TEs in adult tissues, in cell culture and in vivo, where they partner up to regulate the expression of cellular genes. Therefore, TEs and KRAB-ZFPs establish widely active transcription networks that regulate not only development but probably also many physiological events. Given the high degree of species-specificity of both TEs and KRAB-ZFPs, these results have important implications for studying and understanding the biology of higher vertebrates, including humans.
Project description:Mammalian genomes encode several hundred Krüppel-associated box zinc finger proteins (KRAB-ZFPs) that bind DNA in a sequence-specific manner through tandem arrays of C2H2-type zinc fingers and repress transcription via KRAB-dependent recruitment of the silencing cofactor KAP1. The KRAB-ZFP family rapidly amplified and diversified in mammals by segmental gene duplications, mutations, and zinc finger rearrangements likely in response to continued transposable element invasions, but the biological functions and in vivo requirement of these proteins has gone largely unexplored. Here we report the identification of the genome-wide binding profiles of 61 mouse KRAB-ZFPs by overexpression of epitope-tagged transgenes. We found that 51 of these KRAB-ZFPs target at least one retrotransposon group. Interestingly, evolutionary young and still active retrotransposons such as IAP and ETn elements are targeted by several KRAB-ZFPs which are mainly encoded within two gene clusters that are not conserved in any other sequenced species. This indicated that an evolutionary arms race drives the rapid expansion of KRAB-ZFP genes in order to restrict active retrotransposons.