Project description:The transcriptional activator MyoD serves as a master controller of myogenesis. Often in partnership with Mef2, MyoD binds to the promoters of hundreds of muscle genes in proliferating myoblasts, yet activates these targets only upon receiving cues that launch differentiation. What regulates this off/on switch of MyoD function has been incompletely understood, although known to reflect the action of chromatin modifiers. Here, we identify KAP1/TRIM28 as a key regulator of MyoD function. In myoblasts, KAP1 is present with MyoD and Mef2 at many muscle genes, where it acts as a scaffold to recruit not only co-activators such as p300 and LSD1, but also co-repressors such as G9a and HDAC1, with promoter silencing as net outcome. Upon differentiation, MSK1-mediated phosphorylation of KAP1 releases the co-repressors from the scaffold, unleashing transcriptional activation by MyoD/Mef2 and their positive cofactors. Thus, our results reveal KAP1 as a previously unappreciated interpreter of cell signaling, which modulates the ability of MyoD to drive myogenesis. Kap1 and H3K9me3 ChIPseq in proliferating C2C12 cells
Project description:The ATP dependent chromatin remodeler SMARCAD1 and the co-repressor KAP1 (Trim28/Tif1 beta) interact directly. We wanted to understand the interplay between these two proteins in the context of chromatin; in particular at repetitive sequences. Therefore, we carried out an investigation in E14 ES cells of the genome wide binding behaviour of KAP1 and FLAG-tagged SMARCAD1; both wild-type SMARCAD1 and a catalytically inactive mutant. The E14 cells analysed were either wild-type or depleted for endogenous SMARCAD1 protein. FLAG and KAP1 ChIP was performed on double-cross linked chromatin and sequenced on an Illumina HiSeq1500 with matched input controls. A FLAG antibody precipitation was carried out on cells not expressing FLAG tagged protein as an additional control.
Project description:A current model for the genomic recruitment of Kap1 is via its interaction with KRAB domain-containing zinc finger transcription factors. We have performed ChIP-seq for various mutant KAP1 proteins and shown that this recruitment mechanism mediates binding of KAP1 only to the 3M-CM-"M-BM-^@M-BM-^Y ends of zinc finger genes and that other factors are involved in recruiting KAP1 to promoter regions. 17 total ChIP-seq datasets; three different FLAG-KAP1 mutants, one FLAG-KAP1 wild type, and four different Input datasets from 4 different stable cell lines derived from HEK293 cells: 1 FLAG-KAP1 wild type dataset and 1 Input dataset done from HEK293 stable cells; 1 FLAG-KAP1 HP1BDmut dataset and 1 Input dataset done from HEK293 stable cells, 1 FLAG-KAP1 N-ter RBCC{delta}mut dataset and 1 Input dataset done from HEK293 stable cells, 1 FLAG-KAP1 C-ter PB{delta}mut dataset and 1 Input dataset done from HEK293 stable cells. One FLAG-KAP1 N/C-ter (RBCC+PB){delta}mut dataset done from T-REx HEK293 stable cells. One endogenous KAP1 dataset done from HEK293 cells. Two independent ELK4 datasets done from duplicate HEK293 cells. One endogenous Kap1 dataset and one Input dataset from a stable cell line derived from U2OS cells.
Project description:We show that a hitherto poorly characterized KRAB domain-containing zinc-finger (ZF) transcription factor, ZFP30, positively regulates adipogenesis. We demonstrate ZFP30’s function in murine in vitro and in vivo models, as well as in human stromal vascular fraction cells. We reveal through mechanistic studies that ZFP30 directly targets and activates Pparg2 by binding a retrotransposon-derived enhancer, suggesting a process of adipogenic exaptation. We further show that ZFP30 recruits the co-regulator KRAB-associated protein 1 (KAP1), which, surprisingly, acts as a ZFP30 co-activator in this adipogenic context. As neither the commercial ZFP30 antibodies nor four batches of customized ZFP30 antibodies recognized it specifically (data not shown), we performed ChIP-seq in 3T3-L1 cells expressing HA-tagged ZFP30 in a tetracycline-inducible manner, as also previously employed for ZEB1 (Gubelmann et al., 2014). The mRNA expression of exogenous Zfp30 was induced to a similar level as the endogenous Zfp30 by adjusting the amount of Doxycycline (data not shown), to avoid potential artefacts due to protein overexpression. To further characterize its role in adipogenesis and as a ZFP30 partner, we performed KAP1 ChIP-seq in undifferentiated (day 0) and differentiated (day 2) 3T3-L1 cells, as described above for HA-ZFP30. We first confirmed the high enrichment obtained with the employed KAP1 antibody.
Project description:Chromatin remodeling is fundamental for B cell differentiation. Here, we explored the role in this process of KAP1, the cofactor of KRAB-ZFP transcriptional repressors. B lymphoid-specific Kap1 knockout mice displayed reduced numbers of mature B cells, lower steady-state levels of antibodies and accelerated rates of decay of neutralizing antibodies following viral immunization. Transcriptome analyses of Kap1-deleted B splenocytes revealed an upregulation of PTEN, the enzymatic counter-actor of PIK3 signaling, and of genes encoding DNA damage response factors, cell-cycle regulators and chemokine receptors. ChIP/seq studies established that KAP1 bound at or close to a number of these genes, and controlled chromatin status at their promoters. Genome-wide, KAP1-binding sites avoided active B cell-specific enhancers and were enriched in repressive histone marks, further supporting a role for this molecule in gene silencing in vivo. Likely responsible for tethering KAP1 to at least some of these targets, a discrete subset of KRAB-ZFPs is enriched in B lymphocytes. This work thus reveals the role of KRAB/KAP1-mediated epigenetic regulation in B cell development and homeostasis. Examination of KAP1 binding sites and H3K9me3 enriched regions in KAP1 wild type and KO mouse B splenocytes.
Project description:Chromatin remodelling at specific genomic loci controls lymphoid differentiation. Here, we investigated the role played in this process by Kruppel-Associated Box (KRAB)- Associated Protein 1 (KAP1), the universal cofactor of KRAB-zinc finger proteins (-ZFPs), a tetrapod-restricted family of transcriptional repressors. T cell-specific Kap1-deleted mice displayed a significant expansion of immature thymocytes, imbalances in CD4+/CD8+ cell ratios and impaired responses to TCR stimulation when compared to littermate KAP1 control mice. Transcriptome and chromatin studies revealed that KAP1 binds T cell-specific cis-acting regulatory elements marked by the H3K9me3 repressive mark and enriched in Ikaros/NuRD complexes. Also, KAP1 directly controls the expression of several genes involved in TCR and cytokine signalling. Among these, regulation of FoxO1 seems to play a major role in this system. Likely responsible for tethering KAP1 to at least part of its genomic targets, a small number of KRAB-ZFPs are selectively expressed in T lymphoid cells. These results reveal the so-far unsuspected yet important role of KAP1-mediated epigenetic regulation in T lymphocyte differentiation and activation. Examination of KAP1 binding sites and H3K9me3-enriched regions in wild type and KAP1 KO mouse thymocytes.
Project description:We have performed ChIP seq analysis to obtain the positions of KAP1 and ZFP57 binding sites in mouse ES cells. By comparing the two lists, we were able to find bona fide sites. ChIP-Seq of HA tagged ZFP57 and KAP1 in mouse ES cells
Project description:Heterochromatin binding protein HP1β plays an important role in chromatin organization and cell differentiation, however the underlying mechanisms remain unclear. Here, we generated HP1β-/- embryonic stem cells and observed reduced heterochromatin clustering and impaired differentiation. We found that during stem cell differentiation, HP1β is phosphorylated at serine 89 by CK2, which creates a binding site for the pluripotency regulator KAP1. This phosphorylation dependent sequestration of KAP1 in heterochromatin compartments causes a downregulation of pluripotency factors and triggers pluripotency exit. Accordingly, HP1β-/- and phospho-mutant cells exhibited impaired differentiation, while ubiquitination-deficient KAP1ΔRing cells had the opposite phenotype with enhanced differentiation. These results suggest that KAP1 regulates pluripotency via its ubiquitination activity. We propose that the formation of subnuclear membraneless heterochromatin compartments may serve as a dynamic reservoir to trap or release cellular factors. The sequestration of essential regulators defines a novel and active role of heterochromatin in gene regulation and represents a dynamic mode of remote control to regulate cellular processes like cell fate decisions.
Project description:The transcriptional activator MyoD serves as a master controller of myogenesis. Often in partnership with Mef2, MyoD binds to the promoters of hundreds of muscle genes in proliferating myoblasts, yet activates these targets only upon receiving cues that launch differentiation. What regulates this off/on switch of MyoD function has been incompletely understood, although known to reflect the action of chromatin modifiers. Here, we identify KAP1/TRIM28 as a key regulator of MyoD function. In myoblasts, KAP1 is present with MyoD and Mef2 at many muscle genes, where it acts as a scaffold to recruit not only co-activators such as p300 and LSD1, but also co-repressors such as G9a and HDAC1, with promoter silencing as net outcome. Upon differentiation, MSK1-mediated phosphorylation of KAP1 releases the co-repressors from the scaffold, unleashing transcriptional activation by MyoD/Mef2 and their positive cofactors. Thus, our results reveal KAP1 as a previously unappreciated interpreter of cell signaling, which modulates the ability of MyoD to drive myogenesis.