RESUMO
During X-inactivation, Xist RNA spreads along an entire chromosome to establish silencing. However, the mechanism and functional RNA elements involved in spreading remain undefined. By performing a comprehensive endogenous Xist deletion screen, we identify Repeat B as crucial for spreading Xist and maintaining Polycomb repressive complexes 1 and 2 (PRC1/PRC2) along the inactive X (Xi). Unexpectedly, spreading of these three factors is inextricably linked. Deleting Repeat B or its direct binding partner, HNRNPK, compromises recruitment of PRC1 and PRC2. In turn, ablating PRC1 or PRC2 impairs Xist spreading. Therefore, Xist and Polycomb complexes require each other to propagate along the Xi, suggesting a positive feedback mechanism between RNA initiator and protein effectors. Perturbing Xist/Polycomb spreading causes failure of de novo Xi silencing, with partial compensatory downregulation of the active X, and also disrupts topological Xi reconfiguration. Thus, Repeat B is a multifunctional element that integrates interdependent Xist/Polycomb spreading, silencing, and changes in chromosome architecture.
Assuntos
Fibroblastos/metabolismo , Deleção de Genes , Inativação Gênica , Células-Tronco Embrionárias Murinas/metabolismo , Complexo Repressor Polycomb 1/genética , Complexo Repressor Polycomb 2/genética , RNA Longo não Codificante/genética , Inativação do Cromossomo X , Cromossomo X/genética , Animais , Linhagem Celular Transformada , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Ribonucleoproteínas Nucleares Heterogêneas Grupo K , Masculino , Camundongos , Motivos de Nucleotídeos , Complexo Repressor Polycomb 1/metabolismo , Complexo Repressor Polycomb 2/metabolismo , Ligação Proteica , RNA Longo não Codificante/metabolismo , Sequências Repetitivas de Ácido Nucleico , Ribonucleoproteínas/genética , Ribonucleoproteínas/metabolismo , Cromossomo X/metabolismoRESUMO
Highly structured RNA molecules usually interact with each other, and associate with various RNA-binding proteins, to regulate critical biological processes. However, RNA structures and interactions in intact cells remain largely unknown. Here, by coupling proximity ligation mediated by RNA-binding proteins with deep sequencing, we report an RNA in situ conformation sequencing (RIC-seq) technology for the global profiling of intra- and intermolecular RNA-RNA interactions. This technique not only recapitulates known RNA secondary structures and tertiary interactions, but also facilitates the generation of three-dimensional (3D) interaction maps of RNA in human cells. Using these maps, we identify noncoding RNA targets globally, and discern RNA topological domains and trans-interacting hubs. We reveal that the functional connectivity of enhancers and promoters can be assigned using their pairwise-interacting RNAs. Furthermore, we show that CCAT1-5L-a super-enhancer hub RNA-interacts with the RNA-binding protein hnRNPK, as well as RNA derived from the MYC promoter and enhancer, to boost MYC transcription by modulating chromatin looping. Our study demonstrates the power and applicability of RIC-seq in discovering the 3D structures, interactions and regulatory roles of RNA.
Assuntos
Conformação de Ácido Nucleico , RNA/química , RNA/genética , Análise de Sequência de RNA/métodos , Linhagem Celular , Cromatina/genética , Cromatina/metabolismo , Cromossomos Humanos/genética , Elementos Facilitadores Genéticos/genética , Genes myc/genética , Genes de RNAr/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Humanos , Regiões Promotoras Genéticas/genética , RNA Longo não Codificante/química , RNA Longo não Codificante/genética , Reprodutibilidade dos Testes , Transcrição GênicaRESUMO
Translation initiation of the human immunodeficiency virus-type 1 (HIV-1) genomic mRNA (vRNA) is cap-dependent or mediated by an internal ribosome entry site (IRES). The HIV-1 IRES requires IRES-transacting factors (ITAFs) for function. In this study, we evaluated the role of the heterogeneous nuclear ribonucleoprotein K (hnRNPK) as a potential ITAF for the HIV-1 IRES. In HIV-1-expressing cells, the depletion of hnRNPK reduced HIV-1 vRNA translation. Furthermore, both the depletion and overexpression of hnRNPK modulated HIV-1 IRES activity. Phosphorylations and protein arginine methyltransferase 1 (PRMT1)-induced asymmetrical dimethylation (aDMA) of hnRNPK strongly impacted the protein's ability to promote the activity of the HIV-1 IRES. We also show that hnRNPK acts as an ITAF for the human T cell lymphotropic virus-type 1 (HTLV-1) IRES, present in the 5'UTR of the viral sense mRNA, but not for the IRES present in the antisense spliced transcript encoding the HTLV-1 basic leucine zipper protein (sHBZ). This study provides evidence for a novel role of the host hnRNPK as an ITAF that stimulates IRES-mediated translation initiation for the retroviruses HIV-1 and HTLV-1.
Assuntos
Ribonucleoproteínas Nucleares Heterogêneas Grupo K , Retroviridae , Humanos , Regiões 5' não Traduzidas , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Sítios Internos de Entrada Ribossomal/genética , Fosforilação , Biossíntese de Proteínas , Processamento de Proteína Pós-Traducional , Proteína-Arginina N-Metiltransferases/metabolismo , Proteínas Repressoras/metabolismo , Retroviridae/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
Although large exons cannot be readily recognized by the spliceosome, many are evolutionarily conserved and constitutively spliced for inclusion in the processed transcript. Furthermore, whether large exons may be enriched in a certain subset of proteins, or mediate specific functions, has remained unclear. Here, we identify a set of nearly 3,000 SRSF3-dependent large constitutive exons (S3-LCEs) in human and mouse cells. These exons are enriched for cytidine-rich sequence motifs, which bind and recruit the splicing factors hnRNP K and SRSF3. We find that hnRNP K suppresses S3-LCE splicing, an effect that is mitigated by SRSF3 to thus achieve constitutive splicing of S3-LCEs. S3-LCEs are enriched in genes for components of transcription machineries, including mediator and BAF complexes, and frequently contain intrinsically disordered regions (IDRs). In a subset of analyzed S3-LCE-containing transcription factors, SRSF3 depletion leads to deletion of the IDRs due to S3-LCE exon skipping, thereby disrupting phase-separated assemblies of these factors. Cytidine enrichment in large exons introduces proline/serine codon bias in intrinsically disordered regions and appears to have been evolutionarily acquired in vertebrates. We propose that layered splicing regulation by hnRNP K and SRSF3 ensures proper phase-separation of these S3-LCE-containing transcription factors in vertebrates.
Assuntos
Éxons , Fatores de Processamento de Serina-Arginina/genética , Fatores de Transcrição/genética , Vertebrados/genética , Animais , Linhagem Celular , Citidina/genética , Evolução Molecular , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Humanos , Proteínas Intrinsicamente Desordenadas/genética , Proteínas Intrinsicamente Desordenadas/metabolismo , Camundongos , Poliadenilação , Splicing de RNA , Proteínas de Ligação a RNA/genética , Fatores de Processamento de Serina-Arginina/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Au-Kline syndrome (AKS) is a neurodevelopmental disorder associated with multiple malformations and a characteristic facial gestalt. The first individuals ascertained carried de novo loss-of-function (LoF) variants in HNRNPK. Here, we report 32 individuals with AKS (26 previously unpublished), including 13 with de novo missense variants. We propose new clinical diagnostic criteria for AKS that differentiate it from the clinically overlapping Kabuki syndrome and describe a significant phenotypic expansion to include individuals with missense variants who present with subtle facial features and few or no malformations. Many gene-specific DNA methylation (DNAm) signatures have been identified for neurodevelopmental syndromes. Because HNRNPK has roles in chromatin and epigenetic regulation, we hypothesized that pathogenic variants in HNRNPK may be associated with a specific DNAm signature. Here, we report a unique DNAm signature for AKS due to LoF HNRNPK variants, distinct from controls and Kabuki syndrome. This DNAm signature is also identified in some individuals with de novo HNRNPK missense variants, confirming their pathogenicity and the phenotypic expansion of AKS to include more subtle phenotypes. Furthermore, we report that some individuals with missense variants have an "intermediate" DNAm signature that parallels their milder clinical presentation, suggesting the presence of an epi-genotype phenotype correlation. In summary, the AKS DNAm signature may help elucidate the underlying pathophysiology of AKS. This DNAm signature also effectively supported clinical syndrome delineation and is a valuable aid for variant interpretation in individuals where a clinical diagnosis of AKS is unclear, particularly for mild presentations.
Assuntos
Metilação de DNA , Deficiência Intelectual , Anormalidades Múltiplas , Cromatina , Metilação de DNA/genética , Epigênese Genética , Face/anormalidades , Doenças Hematológicas , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Humanos , Deficiência Intelectual/genética , Fenótipo , Doenças VestibularesRESUMO
Recently, more than 1000 large intergenic noncoding RNAs (lincRNAs) have been reported. These RNAs are evolutionarily conserved in mammalian genomes and thus presumably function in diverse biological processes. Here, we report the identification of lincRNAs that are regulated by p53. One of these lincRNAs (lincRNA-p21) serves as a repressor in p53-dependent transcriptional responses. Inhibition of lincRNA-p21 affects the expression of hundreds of gene targets enriched for genes normally repressed by p53. The observed transcriptional repression by lincRNA-p21 is mediated through the physical association with hnRNP-K. This interaction is required for proper genomic localization of hnRNP-K at repressed genes and regulation of p53 mediates apoptosis. We propose a model whereby transcription factors activate lincRNAs that serve as key repressors by physically associating with repressive complexes and modulate their localization to sets of previously active genes.
Assuntos
Regulação para Baixo , RNA não Traduzido/metabolismo , Proteína Supressora de Tumor p53/metabolismo , Animais , Apoptose , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Humanos , Camundongos , Dados de Sequência Molecular , Transcrição GênicaRESUMO
Osteoarthritis (OA) is an age-related or post-traumatic degenerative whole joint disease characterized by the rupture of articular cartilage homeostasis, the regulatory mechanisms of which remain elusive. This study identifies the essential role of heterogeneous nuclear ribonucleoprotein K (hnRNPK) in maintaining articular cartilage homeostasis. Hnrnpk expression is markedly downregulated in human and mice OA cartilage. The deletion of Hnrnpk effectively accelerates the development of post-traumatic and age-dependent OA in mice. Mechanistically, the KH1 and KH2 domain of Hnrnpk bind and degrade the mRNA of WWC1. Hnrnpk deletion increases WWC1 expression, which in turn leads to the activation of Hippo signaling and ultimately aggravates OA. In particular, intra-articular injection of LPA and adeno-associated virus serotype 5 expressing WWC1 RNA interference ameliorates cartilage degeneration induced by Hnrnpk deletion, and intra-articular injection of adeno-associated virus serotype 5 expressing Hnrnpk protects against OA. Collectively, this study reveals the critical roles of Hnrnpk in inhibiting OA development through WWC1-dependent downregulation of Hippo signaling in chondrocytes and defines a potential target for the prevention and treatment of OA.
Assuntos
Cartilagem Articular , Condrócitos , Ribonucleoproteínas Nucleares Heterogêneas Grupo K , Via de Sinalização Hippo , Osteoartrite , Proteínas Serina-Treonina Quinases , Transdução de Sinais , Animais , Humanos , Masculino , Camundongos , Cartilagem Articular/metabolismo , Cartilagem Articular/patologia , Condrócitos/metabolismo , Dependovirus/genética , Modelos Animais de Doenças , Regulação da Expressão Gênica , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/genética , Osteoartrite/metabolismo , Osteoartrite/genética , Osteoartrite/etiologia , Osteoartrite/patologia , Osteoartrite/terapia , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
The Polycomb-repressive complexes PRC1 and PRC2 play a key role in chromosome silencing induced by the non-coding RNA Xist. Polycomb recruitment is initiated by the PCGF3/5-PRC1 complex, which catalyzes chromosome-wide H2A lysine 119 ubiquitylation, signaling recruitment of other PRC1 complexes, and PRC2. However, the molecular mechanism for PCGF3/5-PRC1 recruitment by Xist RNA is not understood. Here we define the Xist RNA Polycomb Interaction Domain (XR-PID), a 600 nt sequence encompassing the Xist B-repeat element. Deletion of XR-PID abolishes Xist-dependent Polycomb recruitment, in turn abrogating Xist-mediated gene silencing and reversing Xist-induced chromatin inaccessibility. We identify the RNA-binding protein hnRNPK as the principal XR-PID binding factor required to recruit PCGF3/5-PRC1. Accordingly, synthetically tethering hnRNPK to Xist RNA lacking XR-PID is sufficient for Xist-dependent Polycomb recruitment. Our findings define a key pathway for Polycomb recruitment by Xist RNA, providing important insights into mechanisms of chromatin modification by non-coding RNA.
Assuntos
Células-Tronco Embrionárias/metabolismo , Complexo Repressor Polycomb 1/metabolismo , Proteínas do Grupo Polycomb/metabolismo , RNA Longo não Codificante/metabolismo , Ribonucleoproteínas/metabolismo , Inativação do Cromossomo X , Cromossomo X/metabolismo , Animais , Sítios de Ligação , Linhagem Celular , Ribonucleoproteínas Nucleares Heterogêneas Grupo K , Histonas/metabolismo , Lisina/metabolismo , Camundongos , Complexo Repressor Polycomb 1/genética , Proteínas do Grupo Polycomb/genética , Ligação Proteica , Domínios e Motivos de Interação entre Proteínas , Interferência de RNA , RNA Longo não Codificante/genética , Ribonucleoproteínas/genética , Transcrição Gênica , Transfecção , Ubiquitinação , Cromossomo X/genéticaRESUMO
DNA i-motifs (iMs) are non-canonical C-rich secondary structures implicated in numerous cellular processes. Though iMs exist throughout the genome, our understanding of iM recognition by proteins or small molecules is limited to a few examples. We designed a DNA microarray containing 10976 genomic iM sequences to examine the binding profiles of four iM-binding proteins, mitoxantrone and the iMab antibody. iMab microarray screens demonstrated that pH 6.5, 5% BSA buffer was optimal, and fluorescence was correlated with iM C-tract length. hnRNP K broadly recognizes diverse iM sequences, favoring 3-5 cytosine repeats flanked by thymine-rich loops of 1-3 nucleotides. Array binding mirrored public ChIP-Seq datasets, in which 35% of well-bound array iMs are enriched in hnRNP K peaks. In contrast, other reported iM-binding proteins had weaker binding or preferred G-quadruplex (G4) sequences instead. Mitoxantrone broadly binds both shorter iMs and G4s, consistent with an intercalation mechanism. These results suggest that hnRNP K may play a role in iM-mediated regulation of gene expression in vivo, whereas hnRNP A1 and ASF/SF2 are possibly more selective in their binding preferences. This powerful approach represents the most comprehensive investigation of how biomolecules selectively recognize genomic iMs to date.
Assuntos
DNA , Motivos de Nucleotídeos , DNA/química , Quadruplex G , Ribonucleoproteínas Nucleares Heterogêneas Grupo K , Mitoxantrona , Humanos , Análise de Sequência com Séries de OligonucleotídeosRESUMO
Lysosome plays important roles in cellular homeostasis, and its dysregulation contributes to tumor growth and survival. However, the understanding of regulation and the underlying mechanism of lysosome in cancer survival is incomplete. Here, we reveal a role for a histone acetylation-regulated long noncoding RNA termed lysosome cell death regulator (LCDR) in lung cancer cell survival, in which its knockdown promotes apoptosis. Mechanistically, LCDR binds to heterogenous nuclear ribonucleoprotein K (hnRNP K) to regulate the stability of the lysosomal-associated protein transmembrane 5 (LAPTM5) transcript that maintains the integrity of the lysosomal membrane. Knockdown of LCDR, hnRNP K, or LAPTM5 promotes lysosomal membrane permeabilization and lysosomal cell death, thus consequently resulting in apoptosis. LAPTM5 overexpression or cathepsin B inhibitor partially restores the effects of this axis on lysosomal cell death in vitro and in vivo. Similarly, targeting LCDR significantly decreased tumor growth of patient-derived xenografts of lung adenocarcinoma (LUAD) and had significant cell death using nanoparticles (NPs)-mediated systematic short interfering RNA delivery. Moreover, LCDR/hnRNP K/LAPTM5 are up-regulated in LUAD tissues, and coexpression of this axis shows the increased diagnostic value for LUAD. Collectively, we identified a long noncoding RNA that regulates lysosome function at the posttranscriptional level. These findings shed light on LCDR/hnRNP K/LAPTM5 as potential therapeutic targets, and targeting lysosome is a promising strategy in cancer treatment.
Assuntos
Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Proteínas de Membrana/metabolismo , RNA Longo não Codificante/genética , Apoptose/genética , Morte Celular , Linhagem Celular Tumoral , Sobrevivência Celular , China , Expressão Gênica/genética , Regulação Neoplásica da Expressão Gênica/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Humanos , Membranas Intracelulares/metabolismo , Lisossomos/metabolismo , Neoplasias/genéticaRESUMO
OBJECTIVE: Immunotherapy targeting programmed cell death 1 (PDCD1 or PD-1) and its ligands has shown remarkable promise and the regulation mechanism of PD-1 expression has received arising attention in recent years. PDCD1 exon 3 encodes the transmembrane domain and the deletion of exon 3 produces a soluble protein isoform of PD-1 (sPD-1), which can enhance immune response by competing with full-length PD-1 protein (flPD-1 or surface PD-1) on T cell surface. However, the mechanism of PDCD1 exon 3 skipping is unclear. METHODS: The online SpliceAid program and minigene expression system were used to analyze potential splicing factors involved in the splicing event of PDCD1 exon 3. The potential binding motifs of heterogeneous nuclear ribonucleoprotein K (HNRNPK) on exon 3 predicted by SpliceAid were mutated by site-directed mutagenesis technology, which were further verified by pulldown assay. Antisense oligonucleotides (ASOs) targeting the exonic splicing silencer (ESS) on PDCD1 exon 3 were synthesized and screened to suppress the skipping of exon 3. The alternative splicing of PDCD1 exon 3 was analyzed by semiquantitative reverse transcription PCR. Western blot and flow cytometry were performed to detect the surface PD-1 expression in T cells. RESULTS: HNRNPK was screened as a key splicing factor that promoted PDCD1 exon 3 skipping, causing a decrease in flPD-1 expression on T cell membrane and an increase in sPD-1 expression. Mechanically, a key ESS has been identified on exon 3 and can be bound by HNRNPK protein to promote exon 3 skipping. Blocking the interaction between ESS and HNRNPK with an ASO significantly reduced exon 3 skipping. Importantly, HNRNPK can promote exon 3 skipping of mouse Pdcd1 gene as well. CONCLUSIONS: Our study revealed a novel evolutionarily conserved regulatory mechanism of PD-1 expression. The splicing factor HNRNPK markedly promoted PDCD1 exon 3 skipping by binding to the ESS on PDCD1 exon 3, resulting in decreased expression of flPD-1 and increased expression of sPD-1 in T cells.
Assuntos
Éxons , Ribonucleoproteínas Nucleares Heterogêneas Grupo K , Receptor de Morte Celular Programada 1 , Linfócitos T , Receptor de Morte Celular Programada 1/genética , Receptor de Morte Celular Programada 1/metabolismo , Animais , Humanos , Linfócitos T/metabolismo , Linfócitos T/imunologia , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Processamento Alternativo , Camundongos Endogâmicos C57BL , Camundongos , Oligonucleotídeos Antissenso/genéticaRESUMO
Long noncoding RNAs (lncRNAs) are emerging as key parts of multiple cellular pathways, but their modes of action and how these are dictated by sequence remain unclear. lncRNAs tend to be enriched in the nuclear fraction, whereas most mRNAs are overtly cytoplasmic, although several studies have found that hundreds of mRNAs in various cell types are retained in the nucleus. It is thus conceivable that some mechanisms that promote nuclear enrichment are shared between lncRNAs and mRNAs. Here, to identify elements in lncRNAs and mRNAs that can force nuclear localization, we screened libraries of short fragments tiled across nuclear RNAs, which were cloned into the untranslated regions of an efficiently exported mRNA. The screen identified a short sequence derived from Alu elements and bound by HNRNPK that increased nuclear accumulation. Binding of HNRNPK to C-rich motifs outside Alu elements is also associated with nuclear enrichment in both lncRNAs and mRNAs, and this mechanism is conserved across species. Our results thus identify a pathway for regulation of RNA accumulation and subcellular localization that has been co-opted to regulate the fate of transcripts with integrated Alu elements.
Assuntos
Elementos Alu/genética , Núcleo Celular/genética , Transporte de RNA , RNA Longo não Codificante/genética , RNA Longo não Codificante/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transporte Ativo do Núcleo Celular , Animais , Sequência de Bases , Sítios de Ligação , Sequência Conservada , Evolução Molecular , Células HeLa , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Humanos , Células MCF-7 , Camundongos , Especificidade da Espécie , Regiões não Traduzidas/genéticaRESUMO
Heterogeneous nuclear ribonucleoprotein K (hnRNPK) is an RNA-binding protein that regulates multiple biological processes, including paraspeckles formation and cellular signal transduction. Recently, hnRNPK has been shown to interact with SINE-derived nuclear RNA localization (SIRLOIN)-containing RNAs, and orchestrate nuclear enrichment and cellular functions of long noncoding RNAs (lncRNAs). hnRNPK-lncRNAs interaction is potentially implicated in various pathogenic disorders including tumorigenesis, and Kabuki-like, Au-Kline, and Okamoto syndromes.
Assuntos
Fissura Palatina/metabolismo , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Hidronefrose/metabolismo , Deficiência Intelectual/metabolismo , Hipotonia Muscular/metabolismo , Síndromes Paraneoplásicas/metabolismo , RNA Longo não Codificante/metabolismo , Anormalidades Múltiplas/metabolismo , Face/anormalidades , Fácies , Doenças Hematológicas/metabolismo , Humanos , Doenças Vestibulares/metabolismoRESUMO
Fused in sarcoma (FUS) is a pathogenic RNA-binding protein in amyotrophic lateral sclerosis (ALS). We previously reported that FUS stabilizes Synaptic Ras-GTPase activating protein 1 (Syngap1) mRNA at its 3' untranslated region (UTR) and maintains spine maturation. To elucidate the pathologic roles of this mechanism in ALS patients, we identified the SYNGAP1 3'UTR variant rs149438267 in seven (four males and three females) out of 807 ALS patients at the FUS binding site from a multicenter cohort in Japan. Human-induced pluripotent stem cell (hiPSC)-derived motor neurons with the SYNGAP1 variant showed aberrant splicing, increased isoform α1 levels, and decreased isoform γ levels, which caused dendritic spine loss. Moreover, the SYNGAP1 variant excessively recruited FUS and heterogeneous nuclear ribonucleoprotein K (HNRNPK), and antisense oligonucleotides (ASOs) blocking HNRNPK altered aberrant splicing and ameliorated dendritic spine loss. These data suggest that excessive recruitment of RNA-binding proteins, especially HNRNPK, as well as changes in SYNGAP1 isoforms, are crucial for spine formation in motor neurons.SIGNIFICANCE STATEMENT It is not yet known which RNAs cause the pathogenesis of amyotrophic lateral sclerosis (ALS). We previously reported that Fused in sarcoma (FUS), a pathogenic RNA-binding protein in ALS, stabilizes synaptic Ras-GTPase activating protein 1 (Syngap1) mRNA at its 3' untranslated region (UTR) and maintains dendritic spine maturation. To elucidate whether this mechanism is crucial for ALS, we identified the SYNGAP1 3'UTR variant rs149438267 at the FUS binding site. Human-induced pluripotent stem cell (hiPSC)-derived motor neurons with the SYNGAP1 variant showed aberrant splicing, which caused dendritic spine loss along with excessive recruitment of FUS and heterogeneous nuclear ribonucleoprotein K (HNRNPK). Our findings that dendritic spine loss is because of excess recruitment of RNA-binding proteins provide a basis for the future exploration of ALS-related RNA-binding proteins.
Assuntos
Esclerose Lateral Amiotrófica , Sarcoma , Masculino , Feminino , Humanos , Esclerose Lateral Amiotrófica/metabolismo , Regiões 3' não Traduzidas/genética , Proteína FUS de Ligação a RNA/genética , Proteína FUS de Ligação a RNA/metabolismo , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Espinhas Dendríticas/metabolismo , Mutação , Proteínas de Ligação a RNA/genética , RNA Mensageiro/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Proteínas Ativadoras de GTPase/genética , Proteínas Ativadoras de GTPase/metabolismo , Sarcoma/genética , Proteínas Ativadoras de ras GTPase/genéticaRESUMO
I-motifs are four-strand noncanonical secondary structures formed by cytosine (C)-rich sequences in living cells. The structural dynamics of i-motifs play essential roles in many cellular processes, such as telomerase inhibition, DNA replication, and transcriptional regulation. In cells, the structural dynamics of the i-motif can be modulated by the interaction of poly(C)-binding proteins (PCBPs), and the interaction is closely related to human health, through modulating the transcription of oncogenes and telomere stability. Therefore, the mechanisms of how PCBPs interact with i-motif structures are fundamentally important. However, the underlying mechanisms remain elusive. I-motif structures in the promoter of the c-MYC oncogene can be unfolded by heterogeneous nuclear ribonucleoprotein K (hnRNP K), a PCBP, to activate its transcription. Here, we selected this system as an example to comprehensively study the unfolding mechanisms. We found that the promoter sequence containing 5 C-runs preferred folding into type-1245 to type-1234 i-motif structures based on their folding stability, which was further confirmed by single-molecule FRET. In addition, we first revealed that the c-MYC i-motif structure was discretely resolved by hnRNP K through two intermediate states, which were assigned to the opposite hairpin and neighboring hairpin, as further confirmed by site mutations. Furthermore, we found all three KH (hnRNP K homology) domains of hnRNP K could unfold the c-MYC i-motif structure, and KH2 and KH3 were more active than KH1. In conclusion, this study may deepen our understanding of the interactions between i-motifs and PCBPs and may be helpful for drug development.
Assuntos
Proteínas de Transporte , Ribonucleoproteínas Nucleares Heterogêneas Grupo K , Humanos , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Proteínas de Transporte/metabolismo , Proteínas de Ligação a RNA/metabolismo , DNA/metabolismo , Estrutura Secundária de ProteínaRESUMO
Recurrent pregnancy loss (RPL) is a common pathological problem during pregnancy, and its clinical etiology is complex and unclear. Dysfunction of trophoblasts may cause a series of pregnancy complications, including preeclampsia, fetal growth restriction, and RPL. Recently, lncRNAs have been found to be closely related to the occurrence and regulation of pregnancy-related diseases, but few studies have focused on their role in RPL. In this study, we identified a novel lncRNA BBOX1-AS1 that was significantly upregulated in villous tissues and serum of RPL patients. Functionally, BBOX1-AS1 inhibited proliferation, migration, invasion, tube formation and promoted apoptosis of trophoblast cells. Mechanistically, overexpression of BBOX1-AS1 activated the p38 and JNK MAPK signaling pathways by upregulating GADD45A expression. Further studies indicated that BBOX1-AS1 could increase the stability of GADD45A mRNA by binding hnRNPK and ultimately cause abnormal trophoblast function. Collectively, our study highlights that the BBOX1-AS1/hnRNPK/GADD45A axis plays an important role in trophoblast-induced RPL and that BBOX1-AS1 may serve as a potential target for the diagnosis of RPL.
Assuntos
MicroRNAs , Pré-Eclâmpsia , RNA Longo não Codificante , Feminino , Gravidez , Humanos , Trofoblastos/metabolismo , Proliferação de Células/genética , Sistema de Sinalização das MAP Quinases , Pré-Eclâmpsia/metabolismo , RNA Longo não Codificante/genética , RNA Longo não Codificante/metabolismo , Movimento Celular/genética , MicroRNAs/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismoRESUMO
Porcine epidemic diarrhea virus (PEDV) is a re-emerging enteric coronavirus currently spreading in several nations and inflicting substantial financial damages on the swine industry. The currently available coronavirus vaccines do not provide adequate protection against the newly emerging viral strains. It is essential to study the relationship between host antiviral factors and the virus and to investigate the mechanisms underlying host immune response against PEDV infection. This study shows that heterogeneous nuclear ribonucleoprotein K (hnRNP K), the host protein determined by the transcription factor KLF15, inhibits the replication of PEDV by degrading the nucleocapsid (N) protein of PEDV in accordance with selective autophagy. hnRNP K was found to be capable of recruiting the E3 ubiquitin ligase, MARCH8, aiming to ubiquitinate N protein. Then, it was found that the ubiquitinated N protein could be delivered into autolysosomes for degradation by the cargo receptor NDP52, thereby inhibiting PEDV proliferation. Moreover, based on the enhanced MyD88 expression, we found that hnRNP K activated the interferon 1 (IFN-1) signaling pathway. Overall, the data obtained revealed a new mechanism of hnRNP K-mediated virus restriction wherein hnRNP K suppressed PEDV replication by degradation of viral N protein using the autophagic degradation pathway and by induction of IFN-1 production based on upregulation of MyD88 expression. IMPORTANCE The spread of the highly virulent PEDV in many countries is still leading to several epidemic and endemic outbreaks. To elucidate effective antiviral mechanisms, it is important to study the relationship between host antiviral factors and the virus and to investigate the mechanisms underlying host immune response against PEDV infection. In the work, we detected hnRNP K as a new host restriction factor which can hinder PEDV replication through degrading the nucleocapsid protein based on E3 ubiquitin ligase MARCH8 and the cargo receptor NDP52. In addition, via the upregulation of MyD88 expression, hnRNP K could also activate the interferon (IFN) signaling pathway. This study describes a previously unknown antiviral function of hnRNP K and offers a new vision toward host antiviral factors that regulate innate immune response as well as a protein degradation pathway against PEDV infection.
Assuntos
Infecções por Coronavirus , Ribonucleoproteínas Nucleares Heterogêneas Grupo K , Interferon Tipo I , Vírus da Diarreia Epidêmica Suína , Replicação Viral , Animais , Antivirais , Chlorocebus aethiops , Infecções por Coronavirus/veterinária , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Interferons , Fator 88 de Diferenciação Mieloide , Proteínas do Nucleocapsídeo/fisiologia , Vírus da Diarreia Epidêmica Suína/fisiologia , Suínos , Doenças dos Suínos/virologia , Ubiquitina-Proteína Ligases , Células Vero , Interferon Tipo I/imunologiaRESUMO
RNA-binding proteins (RBPs) typically bind to RNA in a sequence-specific manner, resulting in post-transcriptional gene regulation. While the various classes of RNA-binding domains are largely structured, flexible linkers are frequently observed between them. Emerging evidence suggests that these unstructured regions may help spatially position the RNA-binding domains allowing for RNA binding and/or may contribute directly to RNA association via certain sequence motifs contained within them. The importance of these unstructured regions is widely appreciated; however, understanding their contribution to RNA binding, protein stability, and function has been difficult to ascertain. Thus, it is crucial to have a set of rapid and economical assays that do not require specialized instrumentation to study their impact on RBP function. Herein, we discuss the use of plate-based and cell-based thermal shift assays to study the impact of the intrinsically disordered region on the function of a highly conserved RBP, hnRNP K.
Assuntos
Ribonucleoproteínas Nucleares Heterogêneas Grupo K , Proteínas de Ligação a RNA , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Proteínas de Ligação a RNA/metabolismo , RNA/química , Regulação da Expressão Gênica , Ligação ProteicaRESUMO
The research aimed to the influences of the interaction between Y-box-binding protein 1 (YBX1) and heterogeneous nuclear ribonucleoprotein K (HNRNPK) on cell division cycle protein 25 phosphatase A (CDC25a) signal pathway and the regulatory mechanism of lung cancer (LC) metastasis. A total of 34 patients diagnosed with LC pathologically were selected as the research objects, and the expression levels of YBX1, HNRNP and CDC25a in LC non-metastasis tissues and LC metastasis tissues were detected by immunohistochemistry and Western blot (WB). High-expression stable cell lines including YBX1/A549 and HNRNPK /A549 were established in the LC A549 cell strain. The expression levels of YBX1 and HNRNP in YBX1/A549 and HNRNPK /A549 were tested by RT-PCR and WB. Besides, the number of migratory cells YBX1/A549 and HNRNPK /A549 was detected by cell migration experiment, and the influences of the interaction between YBX1 and HNRNP on the expression level of CDC25a were analyzed by co-immunoprecipitation (co-IP). The results showed that the expression level of YBX1 protein in LC metastasis tissues was higher than that in LC non-metastasis tissues (P<0.001). The expression level of HNRNPK protein in LC metastasis tissues was higher than that in LC non-metastasis tissues (P<0.01). The expression level of CDC25a protein in LC metastasis tissues was higher than that in LC non-metastasis tissues (P<0.05). Compared with the Control Group of A549 cell strain and transfected blank plasmid, mRNA levels and relative protein expression levels of YBX1 and HNRNPK in YBX1/A549 and HNRNPK/A549 cell lines were both increased (P<0.001). The number of migratory cells YBX1/A549 and HNRNPK/A549 was increased compared with A549 cells and those in Control Group (P<0.001), and cell migration rate of YBX1/A549 and HNRNPK/A549 was also enhanced compared with A549 cells and those in Control Group (P<0.001). The mRNA and protein levels of YBX1 in YBX1/A549 cell line were increased compared with those in Control Group (P<0.01), and the comparison of mRNA level and protein expression level of HNRNPK in YBX1/A549 cell line with the in Control Group showed no differences (P>0.05). The mRNA level and protein expression level of HNRNPK in HNRNPK/A549 cell line were enhanced compared with those in Control Group (P<0.01), and the comparison of YBX1 level and protein expression level in HNRNPK/A549 cell line with the in Control Group demonstrated no differences (P>0.05). YBX1 antibody adopted in co-IP was coated with magnetic beads, and numerous HNRNPK protein was abundant in YBX1/HNRNPK composite. The mRNA level and protein expression level of YBX1 and HNRNPK in YBX1/A549 and HNRNPK/A549 cell lines were enhanced compared with those in Control Group (P<0.001), and the comparison of mRNA level and protein expression level of CDC25 with those in Control Group showed no differences (P>0.05). The mRNA level and protein expression level of CDC25a in YBX1/HNRNPK/A549 were both higher than those in YBX1/A549 cell line and HNRNPK/A549 (P<0.001). With being induced by YBX1 or HNRNPK, the number of migratory cells CDC25/A549 was increased compared with that in Control Group (P<0.05). The mRNA level and protein expression level of CDC25a in YBX1/HNRNPK/A549 were both significantly higher than those in YBX1/A549 cell line and HNRNPK/A549 (P<0.001). All the above results indicated that the interaction between YBX1 and HNRNP regulated the expression of CDC25a, and further got involved in LC metastasis.
Assuntos
Neoplasias Pulmonares , Humanos , Linhagem Celular Tumoral , Proliferação de Células , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/genética , Ribonucleoproteínas Nucleares Heterogêneas Grupo K/metabolismo , Neoplasias Pulmonares/patologia , RNA Mensageiro/genética , Transdução de Sinais , Proteína 1 de Ligação a Y-Box/genética , Proteína 1 de Ligação a Y-Box/metabolismoRESUMO
Post-transcriptional control is essential to safeguard structural and metabolic changes in enucleated reticulocytes during their terminal maturation to functional erythrocytes. The timely synthesis of arachidonate 15-lipoxygenase (ALOX15), which initiates mitochondria degradation at the final stage of reticulocyte maturation is regulated by the multifunctional protein HNRNPK. It constitutes a silencing complex at the ALOX15 mRNA 3' untranslated region that inhibits translation initiation at the AUG by impeding the joining of ribosomal 60S subunits to 40S subunits. To elucidate how HNRNPK interferes with 80S ribosome assembly, three independent screens were applied. They consistently demonstrated a differential interaction of HNRNPK with RPS19, which is localized at the head of the 40S subunit and extends into its functional center. During induced erythroid maturation of K562 cells, decreasing arginine dimethylation of HNRNPK is linked to a reduced interaction with RPS19 in vitro and in vivo. Dimethylation of residues R256, R258 and R268 in HNRNPK affects its interaction with RPS19. In noninduced K562 cells, RPS19 depletion results in the induction of ALOX15 synthesis and mitochondria degradation. Interestingly, residue W52 in RPS19, which is frequently mutated in Diamond-Blackfan Anemia (DBA), participates in specific HNRNPK binding and is an integral part of a putative aromatic cage.