RESUMEN

Cellular senescence, a stress-induced stable proliferation arrest associated with an inflammatory senescence-associated secretory phenotype (SASP), is a cause of aging. In senescent cells, cytoplasmic chromatin fragments (CCFs) activate SASP via the anti-viral cGAS/STING pathway. Promyelocytic leukemia (PML) protein organizes PML nuclear bodies (NBs), which are also involved in senescence and anti-viral immunity. The HIRA histone H3.3 chaperone localizes to PML NBs in senescent cells. Here, we show that HIRA and PML are essential for SASP expression, tightly linked to HIRA's localization to PML NBs. Inactivation of HIRA does not directly block expression of nuclear factor κB (NF-κB) target genes. Instead, an H3.3-independent HIRA function activates SASP through a CCF-cGAS-STING-TBK1-NF-κB pathway. HIRA physically interacts with p62/SQSTM1, an autophagy regulator and negative SASP regulator. HIRA and p62 co-localize in PML NBs, linked to their antagonistic regulation of SASP, with PML NBs controlling their spatial configuration. These results outline a role for HIRA and PML in the regulation of SASP.

Asunto(s)

Proteínas de Ciclo Celular , Senescencia Celular , Chaperonas de Histonas , Inflamación , FN-kappa B , Proteínas Nucleares , Proteína de la Leucemia Promielocítica , Proteínas Serina-Treonina Quinasas , Proteína Sequestosoma-1 , Transducción de Señal , Factores de Transcripción , Humanos , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Proteínas Adaptadoras Transductoras de Señales/genética , Autofagia , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/genética , Cromatina/metabolismo , Cromatina/genética , Células HEK293 , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/genética , Histonas/metabolismo , Histonas/genética , Inflamación/metabolismo , Inflamación/patología , Inflamación/genética , Proteínas de la Membrana/metabolismo , Proteínas de la Membrana/genética , FN-kappa B/metabolismo , FN-kappa B/genética , Proteínas Nucleares/metabolismo , Proteínas Nucleares/genética , Nucleotidiltransferasas , Proteína de la Leucemia Promielocítica/metabolismo , Proteína de la Leucemia Promielocítica/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Proteína Sequestosoma-1/metabolismo , Proteína Sequestosoma-1/genética , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Proteínas Supresoras de Tumor/metabolismo , Proteínas Supresoras de Tumor/genética

RESUMEN

OBJECTIVE: In past work in budding yeast, we identified a nucleosomal region required for proper interactions between the histone chaperone complex yFACT and transcribed genes. Specific histone mutations within this region cause a shift in yFACT occupancy towards the 3' end of genes, a defect that we have attributed to impaired yFACT dissociation from DNA following transcription. In this work we wished to assess the contributions of DNA sequences at the 3' end of genes in promoting yFACT dissociation upon transcription termination. RESULTS: We generated fourteen different alleles of the constitutively expressed yeast gene PMA1, each lacking a distinct DNA fragment across its 3' end, and assessed their effects on occupancy of the yFACT component Spt16. Whereas most of these alleles conferred no defects on Spt16 occupancy, one did cause a modest increase in Spt16 binding at the gene's 3' end. Interestingly, the same allele also caused minor retention of RNA Polymerase II (Pol II) and altered nucleosome occupancy across the same region of the gene. These results suggest that specific DNA sequences at the 3' ends of genes can play roles in promoting efficient yFACT and Pol II dissociation from genes and can also contribute to proper chromatin architecture.

Asunto(s)

Nucleosomas , ARN Polimerasa II , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Nucleosomas/metabolismo , Nucleosomas/genética , ARN Polimerasa II/metabolismo , ARN Polimerasa II/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Factores de Elongación Transcripcional/genética , Factores de Elongación Transcripcional/metabolismo , Chaperonas de Histonas/genética , Chaperonas de Histonas/metabolismo , ADN de Hongos/genética , ADN de Hongos/metabolismo , Alelos , Secuencia de Bases , Regulación Fúngica de la Expresión Génica , Transcripción Genética

RESUMEN

Breast Cancer Type 1 Susceptibility Protein (BRCA1) is a tumor-suppressor protein that regulates various cellular pathways, including those that are essential for preserving genome stability. One essential mechanism involves a BRCA1-A complex that is recruited to double-strand breaks (DSBs) by RAP80 before initiating DNA damage repair (DDR). How RAP80 itself is recruited to DNA damage sites, however, is unclear. Here, we demonstrate an intrinsic correlation between a methyltransferase DOT1L-mediated RAP80 methylation and BRCA1-A complex chromatin recruitment that occurs during cancer cell radiotherapy resistance. Mechanistically, DOT1L is quickly recruited onto chromatin and methylates RAP80 at multiple lysines in response to DNA damage. Methylated RAP80 is then indispensable for binding to ubiquitinated H2A and subsequently triggering BRCA1-A complex recruitment onto DSBs. Importantly, DOT1L-catalyzed RAP80 methylation and recruitment of BRCA1 have clinical relevance, as inhibition of DOT1L or RAP80 methylation seems to enhance the radiosensitivity of cancer cells both in vivo and in vitro. These data reveal a crucial role for DOT1L in DDR through initiating recruitment of RAP80 and BRCA1 onto chromatin and underscore a therapeutic strategy based on targeting DOT1L to overcome tumor radiotherapy resistance.

Asunto(s)

Proteína BRCA1 , Reparación del ADN , Chaperonas de Histonas , N-Metiltransferasa de Histona-Lisina , Animales , Humanos , Ratones , Proteína BRCA1/metabolismo , Proteína BRCA1/genética , Línea Celular Tumoral , Cromatina/metabolismo , Roturas del ADN de Doble Cadena , Metilación de ADN , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/genética , N-Metiltransferasa de Histona-Lisina/metabolismo , N-Metiltransferasa de Histona-Lisina/genética , Metilación , Metiltransferasas/metabolismo , Proteínas Nucleares/metabolismo , Proteínas Nucleares/genética , Tolerancia a Radiación/genética

RESUMEN

BRCA1, a breast cancer susceptibility gene, has emerged as a central mediator that brings together multiple signaling complexes in response to DNA damage. The A, B, and C complexes of BRCA1, which are formed based on their phosphorylation-dependent interactions with the BRCA1-C-terminal domains, contribute to the roles of BRCA1 in DNA repair and cell cycle checkpoint control. However, their functions in DNA damage response remain to be fully appreciated. Specifically, there has been no systematic investigation of the roles of BRCA1-A, -B, and -C complexes in the regulation of BRCA1 localization and functions, in part because of cellular lethality associated with loss of CtIP protein, which is an essential component in BRCA1-C complex. To systematically investigate the functions of these complexes in DNA damage response, we depleted a key component in each of these complexes. We used the degradation tag system to inducibly deplete endogenous CtIP and obtained a series of RAP80/FANCJ/CtIP single-, double-, and triple-knockout cells. We showed that loss of BRCA1-B/FANCJ and BRCA1-C/CtIP, but not BRCA1-A/RAP80, resulted in reduced cell proliferation and increased sensitivity to DNA damage. BRCA1-C/CtIP and BRCA1-A/RAP80 were involved in BRCA1 recruitment to sites of DNA damage. However, BRCA1-A/RAP80 was not essential for damage-induced BRCA1 localization. Instead, RAP80/H2AX and CtIP have redundant roles in BRCA1 recruitment. Altogether, our systematic analysis uncovers functional differences between BRCA1-A, -B, and -C complexes and provides new insights into the roles of these BRCA1-associated protein complexes in DNA damage response and DNA repair.

Asunto(s)

Proteína BRCA1 , Daño del ADN , Reparación del ADN , Humanos , Proteína BRCA1/metabolismo , Proteína BRCA1/genética , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/genética , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , Proteínas Nucleares/metabolismo , Proteínas Nucleares/genética , Proteínas Portadoras/metabolismo , Proteínas Portadoras/genética , Proteínas del Grupo de Complementación de la Anemia de Fanconi/metabolismo , Proteínas del Grupo de Complementación de la Anemia de Fanconi/genética , Línea Celular Tumoral

RESUMEN

Appropriate responses to environmental challenges are imperative for the survival of all living organisms. Exposure to low-dose stresses is recognized to yield increased cellular fitness, a phenomenon termed hormesis. However, our molecular understanding of how cells respond to low-dose stress remains profoundly limited. Here we report that histone variant H3.3-specific chaperone, HIRA, is required for acquired tolerance, where low-dose heat stress exposure confers resistance to subsequent lethal heat stress. We found that human HIRA activates stress-responsive genes, including HSP70, by depositing histone H3.3 following low-dose stresses. These genes are also marked with histone H3 Lys-4 trimethylation and H3 Lys-9 acetylation, both active chromatin markers. Moreover, depletion of HIRA greatly diminished acquired tolerance, both in normal diploid fibroblasts and in HeLa cells. Collectively, our study revealed that HIRA is required for eliciting adaptive stress responses under environmental fluctuations and is a master regulator of stress tolerance.

Asunto(s)

Proteínas de Ciclo Celular , Respuesta al Choque Térmico , Chaperonas de Histonas , Histonas , Factores de Transcripción , Humanos , Histonas/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/genética , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/genética , Células HeLa , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Respuesta al Choque Térmico/genética , Estrés Fisiológico/genética , Acetilación , Proteínas HSP70 de Choque Térmico/metabolismo , Proteínas HSP70 de Choque Térmico/genética , Fibroblastos/metabolismo , Adaptación Fisiológica/genética

RESUMEN

Our recent studies revealed the role of mouse Aprataxin PNK-like Factor (APLF) in development. Nevertheless, the comprehensive characterization of mouse APLF remains entirely unexplored. Based on domain deletion studies, here we report that mouse APLF's Acidic Domain and Fork Head Associated (FHA) domain can chaperone histones and repair DNA like the respective human orthologs. Immunofluorescence studies in mouse embryonic stem cells showed APLF co-localized with γ-tubulin within and around the centrosomes and govern the number and integrity of centrosomes via PLK4 phosphorylation. Enzymatic analysis established mouse APLF as a kinase. Docking studies identified three putative ATP binding sites within the FHA domain. Site-directed mutagenesis showed that R37 residue within the FHA domain is indispensable for the kinase activity of APLF thereby regulating the centrosome number. These findings might assist us comprehend APLF in different pathological and developmental conditions and reveal non-canonical kinase activity of proteins harbouring FHA domains that might impact multiple cellular processes.

Asunto(s)

Centrosoma , Células Madre Embrionarias de Ratones , Proteínas Serina-Treonina Quinasas , Animales , Centrosoma/metabolismo , Ratones , Células Madre Embrionarias de Ratones/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/genética , Fosforilación

RESUMEN

The evolutionarily conserved HIRA/Hir histone chaperone complex and ASF1a/Asf1 co-chaperone cooperate to deposit histone (H3/H4)2 tetramers on DNA for replication-independent chromatin assembly. The molecular architecture of the HIRA/Hir complex and its mode of histone deposition have remained unknown. Here, we report the cryo-EM structure of the S. cerevisiae Hir complex with Asf1/H3/H4 at 2.9-6.8 Å resolution. We find that the Hir complex forms an arc-shaped dimer with a Hir1/Hir2/Hir3/Hpc2 stoichiometry of 2/4/2/4. The core of the complex containing two Hir1/Hir2/Hir2 trimers and N-terminal segments of Hir3 forms a central cavity containing two copies of Hpc2, with one engaged by Asf1/H3/H4, in a suitable position to accommodate a histone (H3/H4)2 tetramer, while the C-terminal segments of Hir3 harbor nucleic acid binding activity to wrap DNA around the Hpc2-assisted histone tetramer. The structure suggests a model for how the Hir/Asf1 complex promotes the formation of histone tetramers for their subsequent deposition onto DNA.

Asunto(s)

Proteínas de Ciclo Celular , Microscopía por Crioelectrón , Chaperonas de Histonas , Histonas , Unión Proteica , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Histonas/metabolismo , Histonas/química , Histonas/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/química , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/ultraestructura , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/genética , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/química , Chaperonas de Histonas/genética , Modelos Moleculares , Chaperonas Moleculares/metabolismo , Chaperonas Moleculares/química , Chaperonas Moleculares/genética , Multimerización de Proteína , Sitios de Unión , Factores de Transcripción/metabolismo , Factores de Transcripción/química , Factores de Transcripción/genética , Dominios y Motivos de Interacción de Proteínas

RESUMEN

Merkel Cell Carcinoma (MCC) is a rare neuroendocrine skin cancer. In our previous work, we decoded genes specifically deregulated by MCPyV early genes as opposed to other polyomaviruses and established functional importance of NDRG1 in inhibiting cellular proliferation and migration in MCC. In the present work, we found the SET protein, (I2PP2A, intrinsic inhibitor of PP2A) upstream of NDRG1 which was modulated by MCPyV early genes, both in hTERT-HK-MCPyV and MCPyV-positive (+) MCC cell lines. Additionally, MCC dermal tumour nodule tissues showed strong SET expression. Inhibition of the SET-PP2A interaction in hTERT-HK-MCPyV using the small molecule inhibitor, FTY720, increased NDRG1 expression and inhibited cell cycle regulators, cyclinD1 and CDK2. SET inhibition by shRNA and FTY720 also decreased cell proliferation and colony formation in MCPyV(+) MCC cells. Overall, these results pave a path for use of drugs targeting SET protein for the treatment of MCC.

Asunto(s)

Carcinoma de Células de Merkel , Movimiento Celular , Proliferación Celular , Poliomavirus de Células de Merkel , Proteína Fosfatasa 2 , Humanos , Poliomavirus de Células de Merkel/fisiología , Poliomavirus de Células de Merkel/genética , Proteína Fosfatasa 2/metabolismo , Proteína Fosfatasa 2/genética , Carcinoma de Células de Merkel/virología , Carcinoma de Células de Merkel/metabolismo , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/genética , Clorhidrato de Fingolimod/farmacología , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Péptidos y Proteínas de Señalización Intracelular/genética , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Línea Celular Tumoral , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/genética , Infecciones por Polyomavirus/virología , Neoplasias Cutáneas/virología , Neoplasias Cutáneas/patología , Neoplasias Cutáneas/metabolismo , Quinasa 2 Dependiente de la Ciclina/metabolismo , Quinasa 2 Dependiente de la Ciclina/genética

RESUMEN

At the molecular scale, adaptive advantages during plant growth and development rely on modulation of gene expression, primarily provided by epigenetic machinery. One crucial part of this machinery is histone posttranslational modifications, which form a flexible system, driving transient changes in chromatin, and defining particular epigenetic states. Posttranslational modifications work in concert with replication-independent histone variants further adapted for transcriptional regulation and chromatin repair. However, little is known about how such complex regulatory pathways are orchestrated and interconnected in cells. In this work, we demonstrate the utility of mass spectrometry-based approaches to explore how different epigenetic layers interact in Arabidopsis mutants lacking certain histone chaperones. We show that defects in histone chaperone function (e.g., chromatin assembly factor-1 or nucleosome assembly protein 1 mutations) translate into an altered epigenetic landscape, which aids the plant in mitigating internal instability. We observe changes in both the levels and distribution of H2A.W.7, altogether with partial repurposing of H3.3 and changes in the key repressive (H3K27me1/2) or euchromatic marks (H3K36me1/2). These shifts in the epigenetic profile serve as a compensatory mechanism in response to impaired integration of the H3.1 histone in the fas1 mutants. Altogether, our findings suggest that maintaining genome stability involves a two-tiered approach. The first relies on flexible adjustments in histone marks, while the second level requires the assistance of chaperones for histone variant replacement.

Asunto(s)

Proteínas de Arabidopsis , Arabidopsis , Epigénesis Genética , Chaperonas de Histonas , Histonas , Arabidopsis/genética , Arabidopsis/metabolismo , Histonas/metabolismo , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/genética , Mutación , Procesamiento Proteico-Postraduccional , Regulación de la Expresión Génica de las Plantas , Factor 1 de Ensamblaje de la Cromatina/metabolismo , Factor 1 de Ensamblaje de la Cromatina/genética

RESUMEN

The RNA polymerase II (Pol II) elongation rate influences poly(A) site selection, with slow and fast Pol II derivatives causing upstream and downstream shifts, respectively, in poly(A) site utilization. In yeast, depletion of either of the histone chaperones FACT or Spt6 causes an upstream shift of poly(A) site use that strongly resembles the poly(A) profiles of slow Pol II mutant strains. Like slow Pol II mutant strains, FACT- and Spt6-depleted cells exhibit Pol II processivity defects, indicating that both Spt6 and FACT stimulate the Pol II elongation rate. Poly(A) profiles of some genes show atypical downstream shifts; this subset of genes overlaps well for FACT- or Spt6-depleted strains but is different from the atypical genes in Pol II speed mutant strains. In contrast, depletion of histone H3 or H4 causes a downstream shift of poly(A) sites for most genes, indicating that nucleosomes inhibit the Pol II elongation rate in vivo. Thus, chromatin-based control of the Pol II elongation rate is a potential mechanism, distinct from direct effects on the cleavage/polyadenylation machinery, to regulate alternative polyadenylation in response to genetic or environmental changes.

Asunto(s)

Cromatina , Histonas , Poliadenilación , ARN Polimerasa II , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Factores de Elongación Transcripcional , ARN Polimerasa II/metabolismo , ARN Polimerasa II/genética , Cromatina/metabolismo , Cromatina/genética , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Histonas/metabolismo , Factores de Elongación Transcripcional/metabolismo , Factores de Elongación Transcripcional/genética , Nucleosomas/metabolismo , Nucleosomas/genética , Elongación de la Transcripción Genética , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/genética , Poli A/metabolismo

RESUMEN

Histone chaperones and histone variants play crucial roles in DNA replication, gene transcription, and DNA repair in eukaryotes. Histone chaperones reversibly promote nucleosome assembly and disassembly by incorporating or evicting histones and histone variants to modulate chromatin accessibility, thereby altering the chromatin states and modulating DNA-related biological processes. Cofactors assist histone chaperones to target specific chromatin regions to regulate the exchange of histones and histone variants. In this review, we summarize recent progress in the interplay between histone variants and chaperones in plants. We discuss the structural basis of chaperone-histone complexes and the mechanisms of their cooperation in regulating gene transcription and plant development.

Asunto(s)

Chaperonas de Histonas , Histonas , Histonas/metabolismo , Histonas/genética , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/genética , Plantas/metabolismo , Plantas/genética , Cromatina/metabolismo , Cromatina/genética , Proteínas de Plantas/metabolismo , Proteínas de Plantas/genética , Chaperonas Moleculares/metabolismo , Chaperonas Moleculares/genética , Regulación de la Expresión Génica de las Plantas , Nucleosomas/metabolismo

RESUMEN

Histone H3/H4 chaperone anti-silencing function 1 (ASF1) is a conserved factor mediating nucleosomal assembly and disassembly, playing crucial roles in processes such as replication, transcription, and DNA repair. Nevertheless, its involvement in aging has remained unclear. Here, we utilized the model organism Caenorhabditis elegans to demonstrate that the loss of UNC-85, the homolog of ASF1, leads to a shortened lifespan in a multicellular organism. Furthermore, we show that UNC-85 is required for epigenome-mediated longevity, as knockdown of the histone H3 lysine K4 methyltransferase ash-2 does not extend the lifespan of unc-85 mutants. In this context, we found that the longevity-promoting ash-2 RNA interference enhances UNC-85 activity by increasing its nuclear localization. Finally, our data indicate that the loss of UNC-85 increases the activity of one-carbon metabolism, and that downregulation of the one-carbon metabolism component dao-3/MTHFD2 partially rescues the short lifespan of unc-85 mutants. Together, these findings reveal UNC-85/ASF1 as a modulator of the central metabolic pathway and a factor regulating a pro-longevity response, thus shedding light on a mechanism of how nucleosomal maintenance associates with aging.

Asunto(s)

Proteínas de Caenorhabditis elegans , Caenorhabditis elegans , Longevidad , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Animales , Longevidad/genética , Carbono/metabolismo , Chaperonas Moleculares/metabolismo , Chaperonas Moleculares/genética , Histonas/metabolismo , Interferencia de ARN , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/genética , Epigénesis Genética

RESUMEN

Histone chaperones serve a pivotal role in maintaining human physiological processes. They interact with histones in a stable manner, ensuring the accurate and efficient execution of DNA replication, repair and transcription. Retinoblastoma binding protein (RBBP)4 and RBBP7 represent a crucial pair of histone chaperones, which not only govern the molecular behavior of histones H3 and H4, but also participate in the functions of several protein complexes, such as polycomb repressive complex 2 and nucleosome remodeling and deacetylase, thereby regulating the cell cycle, histone modifications, DNA damage and cell fate. A strong association has been indicated between RBBP4/7 and some major human diseases, such as cancer, age­related memory loss and infectious diseases. The present review assesses the molecular mechanisms of RBBP4/7 in regulating cellular biological processes, and focuses on the variations in RBBP4/7 expression and their potential mechanisms in various human diseases, thus providing new insights for their diagnosis and treatment.

Asunto(s)

Histonas , Factores de Transcripción , Humanos , Ciclo Celular , Chaperonas de Histonas/genética , Chaperonas de Histonas/química , Chaperonas de Histonas/metabolismo , Histonas/genética , Histonas/metabolismo , Proteína 4 de Unión a Retinoblastoma/química , Proteína 4 de Unión a Retinoblastoma/metabolismo , Proteína 7 de Unión a Retinoblastoma , Factores de Transcripción/metabolismo

RESUMEN

ABSTRACT: Identifying and targeting microenvironment-driven pathways that are active across acute myeloid leukemia (AML) genetic subtypes should allow the development of more broadly effective therapies. The proinflammatory cytokine interleukin-1ß (IL-1ß) is abundant in the AML microenvironment and promotes leukemic growth. Through RNA-sequencing analysis, we identify that IL-1ß-upregulated ASF1B (antisilencing function-1B), a histone chaperone, in AML progenitors compared with healthy progenitors. ASF1B, along with its paralogous protein ASF1A, recruits H3-H4 histones onto the replication fork during S-phase, a process regulated by Tousled-like kinase 1 and 2 (TLKs). Although ASF1s and TLKs are known to be overexpressed in multiple solid tumors and associated with poor prognosis, their functional roles in hematopoiesis and inflammation-driven leukemia remain unexplored. In this study, we identify that ASF1s and TLKs are overexpressed in multiple genetic subtypes of AML. We demonstrate that depletion of ASF1s significantly reduces leukemic cell growth in both in vitro and in vivo models using human cells. Using a murine model, we show that overexpression of ASF1B accelerates leukemia progression. Moreover, Asf1b or Tlk2 deletion delayed leukemia progression, whereas these proteins are dispensable for normal hematopoiesis. Through proteomics and phosphoproteomics analyses, we uncover that the TLK-ASF1 pathway promotes leukemogenesis by affecting the cell cycle and DNA damage pathways. Collectively, our findings identify the TLK1-ASF1 pathway as a novel mediator of inflammatory signaling and a promising therapeutic target for AML treatment across diverse genetic subtypes. Selective inhibition of this pathway offers potential opportunities to intervene effectively, address intratumoral heterogeneity, and ultimately improve clinical outcomes in AML.

Asunto(s)

Proteínas de Ciclo Celular , Progresión de la Enfermedad , Interleucina-1beta , Leucemia Mieloide Aguda , Proteínas Serina-Treonina Quinasas , Leucemia Mieloide Aguda/metabolismo , Leucemia Mieloide Aguda/patología , Leucemia Mieloide Aguda/genética , Humanos , Animales , Ratones , Interleucina-1beta/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Transducción de Señal , Chaperonas Moleculares/metabolismo , Chaperonas Moleculares/genética , Chaperonas de Histonas/metabolismo , Chaperonas de Histonas/genética , Histonas/metabolismo , Histonas/genética , Línea Celular Tumoral , Factores de Empalme Serina-Arginina/metabolismo , Factores de Empalme Serina-Arginina/genética

RESUMEN

A case of a newborn with tetralogy of Fallot, corpus callosum hypoplasia, and phenotypic features similar to DiGeorge syndrome. Chromosomal microarray analysis did not reveal any alterations. Whole exome sequencing and Sanger sequencing identified a de novo variant in the HIRA gene resulting in the loss of the start codon.

Asunto(s)

Proteínas de Ciclo Celular , Síndrome de DiGeorge , Chaperonas de Histonas , Femenino , Humanos , Recién Nacido , Masculino , Agenesia del Cuerpo Calloso/genética , Proteínas de Ciclo Celular/genética , Síndrome de DiGeorge/genética , Síndrome de DiGeorge/patología , Secuenciación del Exoma , Chaperonas de Histonas/genética , Fenotipo , Tetralogía de Fallot/genética , Factores de Transcripción/genética , Adulto , Linaje

RESUMEN

Chromatin-based epigenetic memory relies on the accurate distribution of parental histone H3-H4 tetramers to newly replicated DNA strands. Mcm2, a subunit of the replicative helicase, and Dpb3/4, subunits of DNA polymerase ε, govern parental histone H3-H4 deposition to the lagging and leading strands, respectively. However, their contribution to epigenetic inheritance remains controversial. Here, using fission yeast heterochromatin inheritance systems that eliminate interference from initiation pathways, we show that a Mcm2 histone binding mutation severely disrupts heterochromatin inheritance, while mutations in Dpb3/4 cause only moderate defects. Surprisingly, simultaneous mutations of Mcm2 and Dpb3/4 stabilize heterochromatin inheritance. eSPAN (enrichment and sequencing of protein-associated nascent DNA) analyses confirmed the conservation of Mcm2 and Dpb3/4 functions in parental histone H3-H4 segregation, with their combined absence showing a more symmetric distribution of parental histone H3-H4 than either single mutation alone. Furthermore, the FACT histone chaperone regulates parental histone transfer to both strands and collaborates with Mcm2 and Dpb3/4 to maintain parental histone H3-H4 density and faithful heterochromatin inheritance. These results underscore the importance of both symmetric distribution of parental histones and their density at daughter strands for epigenetic inheritance and unveil distinctive properties of parental histone chaperones during DNA replication.

Asunto(s)

Histonas , Schizosaccharomyces , Histonas/metabolismo , Chaperonas de Histonas/genética , Chaperonas de Histonas/metabolismo , Heterocromatina/genética , Replicación del ADN/genética , ADN/metabolismo , Schizosaccharomyces/genética , Schizosaccharomyces/metabolismo , Epigénesis Genética

RESUMEN

The disruption of chromatin structure can result in transcription initiation from cryptic promoters within gene bodies. While the passage of RNA polymerase II is a well-characterized chromatin-disrupting force, numerous factors, including histone chaperones, normally stabilize chromatin on transcribed genes, thereby repressing cryptic transcription. DNA replication, which employs a partially overlapping set of histone chaperones, is also inherently disruptive to chromatin, but a role for DNA replication in cryptic transcription has never been examined. In this study, we tested the hypothesis that, in the absence of chromatin-stabilizing factors, DNA replication can promote cryptic transcription in Saccharomyces cerevisiae. Using a novel fluorescent reporter assay, we show that multiple factors, including Asf1, CAF-1, Rtt106, Spt6, and FACT, block transcription from a cryptic promoter, but are entirely or partially dispensable in G1-arrested cells, suggesting a requirement for DNA replication in chromatin disruption. Collectively, these results demonstrate that transcription fidelity is dependent on numerous factors that function to assemble chromatin on nascent DNA.

Asunto(s)

Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Histonas/metabolismo , Proteínas Nucleares/genética , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Transcripción Genética , Cromatina/genética , Chaperonas de Histonas/genética , ADN , Chaperonas Moleculares/metabolismo

RESUMEN

HIRIP3 is a mammalian protein homologous to the yeast H2A.Z deposition chaperone Chz1. However, the structural basis underlying Chz's binding preference for H2A.Z over H2A, as well as the mechanism through which Chz1 modulates histone deposition or replacement, remains enigmatic. In this study, we aimed to characterize the function of HIRIP3 and to identify its interacting partners in HeLa cells. Our findings reveal that HIRIP3 is specifically associated in vivo with H2A-H2B dimers and CK2 kinase. While bacterially expressed HIRIP3 exhibited a similar binding affinity towards H2A and H2A.Z, the associated CK2 kinase showed a notable preference for H2A phosphorylation at serine 1. The recombinant HIRIP3 physically interacted with the H2A αC helix through an extended CHZ domain and played a crucial role in depositing the canonical core histones onto naked DNA. Our results demonstrate that mammalian HIRIP3 acts as an H2A histone chaperone, assisting in its selective phosphorylation by Ck2 kinase at serine 1 and facilitating its deposition onto chromatin.

Asunto(s)

Chaperonas de Histonas , Histonas , Animales , Humanos , Células HeLa , Chaperonas de Histonas/genética , Histonas/metabolismo , Mamíferos/metabolismo , Chaperonas Moleculares/metabolismo , Saccharomyces cerevisiae/metabolismo , Serina , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo

RESUMEN

In S phase, duplicating and assembling the whole genome into chromatin requires upregulation of replicative histone gene expression. Here, we explored how histone chaperones control histone production in human cells to ensure a proper link with chromatin assembly. Depletion of the ASF1 chaperone specifically decreases the pool of replicative histones both at the protein and RNA levels. The decrease in their overall expression, revealed by total RNA sequencing (RNA-seq), contrasted with the increase in nascent/newly synthesized RNAs observed by 4sU-labeled RNA-seq. Further inspection of replicative histone RNAs showed a 3' end processing defect with an increase of pre-mRNAs/unprocessed transcripts likely targeted to degradation. Collectively, these data argue for a production defect of replicative histone RNAs in ASF1-depleted cells. We discuss how this regulation of replicative histone RNA metabolism by ASF1 as a "chaperone checkpoint" fine-tunes the histone dosage to avoid unbalanced situations deleterious for cell survival.

Asunto(s)

Histonas , Proteínas de Saccharomyces cerevisiae , Humanos , Histonas/genética , Histonas/metabolismo , Chaperonas de Histonas/genética , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Replicación del ADN , Chaperonas Moleculares/genética , Chaperonas Moleculares/metabolismo , ARN/genética , Proteínas de Saccharomyces cerevisiae/metabolismo

RESUMEN

H3.3, the most common replacement variant for histone H3, has emerged as an important player in chromatin dynamics for controlling gene expression and genome integrity. While replicative variants H3.1 and H3.2 are primarily incorporated into nucleosomes during DNA synthesis, H3.3 is under the control of H3.3-specific histone chaperones for spatiotemporal incorporation throughout the cell cycle. Over the years, there has been progress in understanding the mechanisms by which H3.3 affects domain structure and function. Furthermore, H3.3 distribution and relative abundance profoundly impact cellular identity and plasticity during normal development and pathogenesis. Recurrent mutations in H3.3 and its chaperones have been identified in neoplastic transformation and developmental disorders, providing new insights into chromatin biology and disease. Here, we review recent findings emphasizing how two distinct histone chaperones, HIRA and DAXX, take part in the spatial and temporal distribution of H3.3 in different chromatin domains and ultimately achieve dynamic control of chromatin organization and function. Elucidating the H3.3 deposition pathways from the available histone pool will open new avenues for understanding the mechanisms by which H3.3 epigenetically regulates gene expression and its impact on cellular integrity and pathogenesis.

Asunto(s)

Proteínas de Ciclo Celular , Cromatina , Proteínas Co-Represoras , Histonas , Chaperonas Moleculares , Factores de Transcripción , Ciclo Celular , División Celular , Cromatina/genética , Chaperonas de Histonas/genética , Humanos , Chaperonas Moleculares/genética , Proteínas Co-Represoras/genética , Factores de Transcripción/genética , Proteínas de Ciclo Celular/genética