RESUMEN
Cancer cell heterogeneity is a major driver of therapy resistance. To characterize resistant cells and their vulnerabilities, we studied the PLZF-RARA variant of acute promyelocytic leukemia, resistant to retinoic acid (RA), using single-cell multiomics. We uncovered transcriptional and chromatin heterogeneity in leukemia cells. We identified a subset of cells resistant to RA with proliferation, DNA replication, and repair signatures that depend on a fine-tuned E2F transcriptional network targeting the epigenetic regulator enhancer of zeste homolog 2 (EZH2). Epigenomic and functional analyses validated the driver role of EZH2 in RA resistance. Targeting pan-EZH2 activities (canonical/noncanonical) was necessary to eliminate leukemia relapse-initiating cells, which underlies a dependency of resistant cells on an EZH2 noncanonical activity and the necessity to degrade EZH2 to overcome resistance. Our study provides critical insights into the mechanisms of RA resistance that allow us to eliminate treatment-resistant leukemia cells by targeting EZH2, thus highlighting a potential targeted therapy approach. Beyond RA resistance and acute promyelocytic leukemia context, our study also demonstrates the power of single-cell multiomics to identify, characterize, and clear therapy-resistant cells.
Asunto(s)
Leucemia Promielocítica Aguda , Humanos , Leucemia Promielocítica Aguda/tratamiento farmacológico , Leucemia Promielocítica Aguda/genética , Leucemia Promielocítica Aguda/metabolismo , Tretinoina/farmacología , Proteína Potenciadora del Homólogo Zeste 2/genética , Receptor alfa de Ácido Retinoico/genética , Receptores de Ácido Retinoico/genética , Factores de Transcripción/genética , Proteínas Nucleares/genéticaRESUMEN
PLZF (promyelocytic leukemia zinc finger) is a transcription factor acting as a global regulator of hematopoietic commitment. PLZF displays an epigenetic specificity by recruiting chromatin-modifying factors but little is known about its role in remodeling chromatin of cells committed toward a given specific hematopoietic lineage. In murine myeloid progenitors, we decipher a new role for PLZF in restraining active genes and enhancers by targeting acetylated lysine 27 of Histone H3 (H3K27ac). Functional analyses reveal that active enhancers bound by PLZF are involved in biological processes related to metabolism and associated with hematopoietic aging. Comparing the epigenome of young and old myeloid progenitors, we reveal that H3K27ac variation at active enhancers is a hallmark of hematopoietic aging. Taken together, these data suggest that PLZF, associated with active enhancers, appears to restrain their activity as an epigenetic gatekeeper of hematopoietic aging.
Asunto(s)
Envejecimiento/genética , Células Madre Hematopoyéticas/metabolismo , Proteína de la Leucemia Promielocítica con Dedos de Zinc/genética , Transcripción Genética , Animales , Diferenciación Celular/genética , Elementos de Facilitación Genéticos , Epigénesis Genética/genética , Regulación del Desarrollo de la Expresión Génica/genética , Histonas/genética , Humanos , Histona Demetilasas con Dominio de Jumonji/genética , Ratones , Células Progenitoras Mieloides/metabolismo , Unión Proteica , Secuencias Reguladoras de Ácidos Nucleicos/genéticaRESUMEN
The transcription factor PLZF (promyelocytic leukemia zinc finger protein) acts as an epigenetic regulator balancing self-renewal and differentiation of hematopoietic cells through binding to various chromatin-modifying factors. First described as a transcriptional repressor, PLZF is also associated with active transcription, although the molecular bases underlying the differences are unknown. Here, we reveal that in a hematopoietic cell line, PLZF is predominantly associated with transcribed genes. Additionally, we identify a new association between PLZF and the histone methyltransferase, EZH2 at the genomic level. We find that co-occupancy of PLZF and EZH2 on chromatin at PLZF target genes is not associated with SUZ12 or trimethylated lysine 27 of histone H3 (H3K27me3) but with the active histone mark H3K4me3 and active transcription. Removal of EZH2 leads to an increase of PLZF binding and increased gene expression. Our results suggest a new role of EZH2 in restricting PLZF positive transcriptional activity independently of its canonical PRC2 activity.
Asunto(s)
Proteína Potenciadora del Homólogo Zeste 2/genética , Complejo Represivo Polycomb 2/genética , Proteína de la Leucemia Promielocítica con Dedos de Zinc/genética , Transcripción Genética , Sitios de Unión/genética , Diferenciación Celular/genética , Línea Celular Tumoral , Autorrenovación de las Células/genética , Cromatina/genética , Regulación de la Expresión Génica/genética , Células Madre Hematopoyéticas/metabolismo , Histona Metiltransferasas/genética , Histonas/genética , Humanos , Proteínas de Neoplasias , Unión Proteica/genética , Factores de TranscripciónRESUMEN
Chronic hepatitis B virus (HBV) infection is a major risk factor for hepatocellular carcinoma (HCC) and current treatments for chronic hepatitis B and HCC are suboptimal. Herein, we identified cellular serine/threonine Polo-like-kinase 1 (PLK1) as a positive effector of HBV replication. The aim of this study was to demonstrate the proviral role of PLK1 in HBV biosynthesis and validate PLK1 inhibition a potential antiviral strategy. To this end, we employed physiologically relevant HBV infection models of primary human hepatocytes (PHHs) and differentiated HepaRG cells in conjunction with pharmacologic PLK1 inhibitors, small interfering RNA (siRNA)-mediated knockdown, and overexpression of constitutively active PLK1 (PLK1CA ). In addition, a humanized liver Fah-/- /Rag2-/- /Il2rg-/- (FRG) mouse model was used to determine the antiviral effect of PLK1 inhibitor BI-2536 on HBV infection in vivo. Finally, in vitro PLK1 kinase assays and site-directed mutagenesis were employed to demonstrate that HBV core protein (HBc) is a PLK1 substrate. We demonstrated that HBV infection activated cellular PLK1 in PHHs and differentiated HepaRG cells. PLK1 inhibition by BI-2536 or siRNA-mediated knockdown suppressed HBV DNA biosynthesis, whereas overexpression of PLK1CA increased it, suggesting that the PLK1 effects on viral biosynthesis are specific and that PLK1 is a proviral cellular factor. Significantly, BI-2536 administration to HBV-infected humanized liver FRG mice strongly inhibited HBV infection, validating PLK1 as an antiviral target in vivo. The proviral action of PLK1 is associated with the biogenesis of the nucleocapsid, as BI-2536 leads to its decreased intracellular formation/accumulation. In this respect, our studies identified HBc as a PLK1 substrate in vitro, and mapped PLK1 phosphorylation sites on this protein. CONCLUSION: PLK1 is a proviral host factor that could be envisaged as a target for combined antiviral and antitumoral strategies against HBV infection and HBV-mediated carcinogenesis. (Hepatology 2017;66:1750-1765).
Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Virus de la Hepatitis B/fisiología , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Proto-Oncogénicas/metabolismo , Pteridinas/uso terapéutico , Proteínas del Núcleo Viral/metabolismo , Replicación Viral , Secuencia de Aminoácidos , Animales , Proteínas de Ciclo Celular/antagonistas & inhibidores , Evaluación Preclínica de Medicamentos , Activación Enzimática , Hepatocitos/enzimología , Interacciones Huésped-Patógeno , Humanos , Ratones , Fosforilación , Cultivo Primario de Células , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Proteínas Proto-Oncogénicas/antagonistas & inhibidores , Pteridinas/farmacología , Quinasa Tipo Polo 1RESUMEN
Condensins associate with DNA and shape mitotic chromosomes. Condensins are enriched nearby highly expressed genes during mitosis, but how this binding is achieved and what features associated with transcription attract condensins remain unclear. Here, we report that condensin accumulates at or in the immediate vicinity of nucleosome-depleted regions during fission yeast mitosis. Two transcriptional coactivators, the Gcn5 histone acetyltransferase and the RSC chromatin-remodelling complex, bind to promoters adjoining condensin-binding sites and locally evict nucleosomes to facilitate condensin binding and allow efficient mitotic chromosome condensation. The function of Gcn5 is closely linked to condensin positioning, since neither the localization of topoisomerase II nor that of the cohesin loader Mis4 is altered in gcn5 mutant cells. We propose that nucleosomes act as a barrier for the initial binding of condensin and that nucleosome-depleted regions formed at highly expressed genes by transcriptional coactivators constitute access points into chromosomes where condensin binds free genomic DNA.
