The nuclear receptor binding SET domain protein 1 (NSD1) is recurrently mutated in human cancers including acute leukemia. We show that NSD1 knockdown alters erythroid clonogenic growth of human CD34
...hematopoietic cells. Ablation of Nsd1 in the hematopoietic system of mice induces a transplantable erythroleukemia. In vitro differentiation of Nsd1
erythroblasts is majorly impaired despite abundant expression of GATA1, the transcriptional master regulator of erythropoiesis, and associated with an impaired activation of GATA1-induced targets. Retroviral expression of wildtype NSD1, but not a catalytically-inactive NSD1
SET-domain mutant induces terminal maturation of Nsd1
erythroblasts. Despite similar GATA1 protein levels, exogenous NSD1 but not NSD
significantly increases the occupancy of GATA1 at target genes and their expression. Notably, exogenous NSD1 reduces the association of GATA1 with the co-repressor SKI, and knockdown of SKI induces differentiation of Nsd1
erythroblasts. Collectively, we identify the NSD1 methyltransferase as a regulator of GATA1-controlled erythroid differentiation and leukemogenesis.
TRIM24 (TIF1α), TRIM28 (TIF1β), and TRIM33 (TIF1γ) are three related cofactors belonging to the tripartite motif superfamily that interact with distinct transcription factors. TRIM24 interacts with ...the liganded retinoic acid (RA) receptor to repress its transcriptional activity. Germ line inactivation of TRIM24 in mice deregulates RA-signaling in hepatocytes leading to the development of hepatocellular carcinoma (HCC). Here we show that TRIM24 can be purified as at least two macromolecular complexes comprising either TRIM33 or TRIM33 and TRIM28. Somatic hepatocyte-specific inactivation of TRIM24, TRIM28, or TRIM33 all promote HCC in a cell-autonomous manner in mice. Moreover, HCC formation upon TRIM24 inactivation is strongly potentiated by further loss of TRIM33. These results demonstrate that the TIF1-related subfamily of TRIM proteins interact both physically and functionally to modulate HCC formation in mice.
Sotos syndrome is an autosomal dominant condition characterized by overgrowth resulting in tall stature and macrocephaly, together with an increased risk of tumorigenesis. The disease is caused by ...loss-of-function mutations and deletions of the nuclear receptor SET domain containing protein-1 (NSD1) gene, which encodes a histone methyltransferase involved in chromatin regulation. However, despite its causal role in Sotos syndrome and the typical accelerated growth of these patients, little is known about the putative contribution of NSD1 to human sporadic malignancies. Here, we report that NSD1 function is abrogated in human neuroblastoma and glioma cells by transcriptional silencing associated with CpG island-promoter hypermethylation. We also demonstrate that the epigenetic inactivation of NSD1 in transformed cells leads to the specifically diminished methylation of the histone lysine residues H4-K20 and H3-K36. The described phenotype is also observed in Sotos syndrome patients with NSD1 genetic disruption. Expression microarray data from NSD1-depleted cells, followed by ChIP analysis, revealed that the oncogene MEIS1 is one of the main NSD1 targets in neuroblastoma. Furthermore, we show that the restoration of NSD1 expression induces tumor suppressor-like features, such as reduced colony formation density and inhibition of cellular growth. Screening a large collection of different tumor types revealed that NSD1 CpG island hypermethylation was a common event in neuroblastomas and gliomas. Most importantly, NSD1 hypermethylation was a predictor of poor outcome in high-risk neuroblastoma. These findings highlight the importance of NSD1 epigenetic inactivation in neuroblastoma and glioma that leads to a disrupted histone methylation landscape and might have a translational value as a prognostic marker.
In previous mass spectrometry and coimmune precipitation studies, we identified tripartite motif-containing 28 (TRIM28; also known as transcriptional intermediary factor1β and Krüppel-associated ...box-associated protein-1) as a cofactor that specifically copurified with an NR2C1/NR2C2 (TR2/TR4) orphan nuclear receptor heterodimer that previous studies had implicated as an embryonic/fetal β-type globin gene repressor. TRIM28 has been characterized as a transcriptional corepressor that can associate with many different transcription factors and can play functional roles in multiple tissues and cell types. Here, we tested the contribution of TRIM28 to globin gene regulation and erythropoiesis using a conditional loss-of-function in vivo model. We discovered that Trim28 genetic loss in the adult mouse leads to defective immature erythropoiesis in the bone marrow and consequently to anemia. We further found that TRIM28 controls erythropoiesis in a cell-autonomous manner by inducibly deleting Trim28 exclusively in hematopoietic cells. Finally, in the absence of TRIM28, we observed increased apoptosis as well as diminished expression of multiple erythroid transcription factors and heme biosynthetic enzymes in immature erythroid cells. Thus, TRIM28 is essential for the cell-autonomous development of immature erythroblasts in the bone marrow.
•Genetic loss of the transcriptional corepressor TRIM28 in adult mice results in deficient adult erythropoiesis in bone marrow, and anemia.•TRIM28 controls the mRNA levels of multiple erythroid transcription factors, heme biosynthetic enzymes, and the apoptotic apparatus.
Recent genetic studies in mice have established that the nuclear receptor coregulator Trim24/Tif1α suppresses hepatocarcinogenesis by inhibiting retinoic acid receptor α (Rara)-dependent ...transcription and cell proliferation. However, Rara targets regulated by Trim24 remain unknown. We report that the loss of Trim24 resulted in interferon (IFN)/STAT pathway overactivation soon after birth (week 5). Despite a transient attenuation of this pathway by the induction of several IFN/STAT pathway repressors later in the disease, this phenomenon became more pronounced in tumors. Remarkably, Rara haplodeficiency, which suppresses tumorigenesis in Trim24−/− mice, prevented IFN/STAT overactivation. Moreover, together with Rara, Trim24 bound to the retinoic acid-responsive element of the Stat1 promoter and repressed its retinoic acid-induced transcription. Altogether, these results identify Trim24 as a novel negative regulator of the IFN/STAT pathway and suggest that this repression through Rara inhibition may prevent liver cancer.
Immunoglobulin class switch recombination (CSR) is initiated by double-stranded DNA breaks (DSBs) in switch regions triggered by activation-induced cytidine deaminase (AID). Although CSR correlates ...with epigenetic modifications at the IgH locus, the relationship between these modifications and AID remains unknown. In this study, we show that during CSR, AID forms a complex with KAP1 (KRAB domain-associated protein 1) and HP1 (heterochromatin protein 1) that is tethered to the donor switch region (Sμ) bearing H3K9me3 (trimethylated histone H3 at lysine 9) in vivo. Furthermore, in vivo disruption of this complex results in impaired AID recruitment to Sμ, inefficient DSB formation, and a concomitant defect in CSR but not in somatic hypermutation. We propose that KAP1 and HP1 tether AID to H3K9me3 residues at the donor switch region, thus providing a mechanism linking AID to epigenetic modifications during CSR.
Hepatocellular carcinoma (HCC) is a major cause of death worldwide. Here, we provide evidence that the ligand-dependent nuclear receptor co-regulator Trim24 (also known as Tif1α) functions in mice as ...a liver-specific tumor suppressor. In Trim24-null mice, hepatocytes fail to execute proper cell cycle withdrawal during the neonatal-to-adult transition and continue to cycle in adult livers, becoming prone to a continuum of cellular alterations that progress toward metastatic HCC. Using pharmacological approaches, we show that inhibition of retinoic acid signaling markedly reduces hepatocyte proliferation in Trim24−/− mice. We further show that deletion of a single retinoic acid receptor alpha (Rara) allele in a Trim24-null background suppresses HCC development and restores wild-type expression of retinoic acid-responsive genes in the liver, thus demonstrating that in this genetic background Rara expresses an oncogenic activity correlating with a dysregulation of the retinoic acid signaling pathway. Our results not only provide genetic evidence that Trim24 and Rara co-regulate hepatocarcinogenesis in an antagonistic manner but also suggest that aberrant activation of Rara is deleterious to liver homeostasis.
KAP1 is an essential cofactor of KRAB-zinc finger proteins, a family of vertebrate-specific epigenetic repressors of largely unknown functions encoded in the hundreds by the mouse and human genomes. ...Here, we report that KAP1 is expressed at high levels and necessary for KRAB-mediated repression in mature neurons of the mouse brain. Mice deleted for KAP1 in the adult forebrain exhibit heightened levels of anxiety-like and exploratory activity and stress-induced alterations in spatial learning and memory. In the hippocampus, a small number of genes are dysregulated, including some imprinted genes. Chromatin analyses of the promoters of two genes markedly upregulated in knockout mice reveal decreased histone 3 K9-trimethylation and increased histone 3 and histone 4 acetylation. We propose a model in which the tethering of KAP1-associated chromatin remodeling factors via KRAB-ZFPs epigenetically controls gene expression in the hippocampus, thereby conditioning responses to behavioral stress.
TIF1β is an essential mammalian transcriptional corepressor. It interacts with the heterochromatin proteins HP1 through a highly conserved motif, the HP1box, and we have previously shown that this ...interaction is essential for the differentiation of F9 cells to occur. Here we address the in vivo functions of the TIF1β–HP1 interaction, by generating mice in which the TIF1β HP1box is mutated, leading to the loss of TIF1β interaction with HP1. The effects of the mutation were monitored in two instances, where TIF1β is known to play key roles: early embryonic development and spermatogenesis. We find that mutating the HP1box of TIF1β disrupts embryonic development soon after gastrulation. This effect is likely caused by the misexpression of TIF1β targets that regulate mitotic progression and pluripotency. In contrast, in Sertoli cells, we found that the absence of TIF1β but not its mutation in the HP1box leads to a clear defect of spermatogenesis characterized by a failure of spermatid release and a testicular degeneration. These data show that the interaction between TIF1β and HP1 is essential for some but not all TIF1β functions in vivo. Furthermore, we observed that TIF1β is dispersed through the nucleoplasm of E7.0 embryos, whereas it is mainly associated with pericentromeric heterochromatin of E8.5 embryos and of Sertoli cells, an association that is lost upon TIF1β HP1box mutation. Altogether, these data provide strong evidence that nuclear organization plays key roles during early embryonic development.
► We have assessed the functional relevance of the interaction between TIF1β and HP1. ► We have mutated TIF1β HP1 HP1box in mice either in germ-line cells or in Sertoli cells. ► This mutation leads to arrest during embryonic development and impaired spermatogenesis. ► These functions correlate with TIF1β association with heterochromatin. ► We conclude that TIF1β/HP1 interaction is essential for most TIF1β functions in vivo.
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