RESUMO
The regulation of protein synthesis contributes to gene expression in both normal physiology and disease, yet kinetic investigations of the human translation mechanism are currently lacking. Using single-molecule fluorescence imaging methods, we have quantified the nature and timing of structural processes in human ribosomes during single-turnover and processive translation reactions. These measurements reveal that functional complexes exhibit dynamic behaviors and thermodynamic stabilities distinct from those observed for bacterial systems. Structurally defined sub-states of pre- and post-translocation complexes were sensitive to specific inhibitors of the eukaryotic ribosome, demonstrating the utility of this platform to probe drug mechanism. The application of three-color single-molecule fluorescence resonance energy transfer (smFRET) methods further revealed a long-distance allosteric coupling between distal tRNA binding sites within ribosomes bearing three tRNAs, which contributed to the rate of processive translation.
Assuntos
Biossíntese de Proteínas , RNA de Transferência/química , Ribossomos/química , Regulação Alostérica , Transferência Ressonante de Energia de Fluorescência , Humanos , RNA de Transferência/metabolismo , Ribossomos/metabolismoRESUMO
Breast cancer is the second leading cause of cancer-related deaths in the United States, with the majority of these deaths due to metastatic lesions rather than the primary tumor. Thus, a better understanding of the etiology of metastatic disease is crucial for improving survival. Using a haplotype mapping strategy in mouse and shRNA-mediated gene knockdown, we identified Rnaseh2c, a scaffolding protein of the heterotrimeric RNase H2 endoribonuclease complex, as a novel metastasis susceptibility factor. We found that the role of Rnaseh2c in metastatic disease is independent of RNase H2 enzymatic activity, and immunophenotyping and RNA-sequencing analysis revealed engagement of the T cell-mediated adaptive immune response. Furthermore, the cGAS-Sting pathway was not activated in the metastatic cancer cells used in this study, suggesting that the mechanism of immune response in breast cancer is different from the mechanism proposed for Aicardi-Goutières Syndrome, a rare interferonopathy caused by RNase H2 mutation. These results suggest an important novel, non-enzymatic role for RNASEH2C during breast cancer progression and add Rnaseh2c to a panel of genes we have identified that together could determine patients with high risk for metastasis. These results also highlight a potential new target for combination with immunotherapies and may contribute to a better understanding of the etiology of Aicardi-Goutières Syndrome autoimmunity.
Assuntos
Imunidade Adaptativa , Doenças Autoimunes do Sistema Nervoso/genética , Neoplasias da Mama/genética , Regulação Neoplásica da Expressão Gênica , Neoplasias Pulmonares/genética , Proteínas de Neoplasias/genética , Malformações do Sistema Nervoso/genética , Ribonuclease H/genética , Animais , Doenças Autoimunes do Sistema Nervoso/imunologia , Doenças Autoimunes do Sistema Nervoso/mortalidade , Doenças Autoimunes do Sistema Nervoso/patologia , Neoplasias da Mama/imunologia , Neoplasias da Mama/mortalidade , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Proliferação de Células , Modelos Animais de Doenças , Feminino , Predisposição Genética para Doença , Humanos , Neoplasias Pulmonares/imunologia , Neoplasias Pulmonares/mortalidade , Neoplasias Pulmonares/secundário , Metástase Linfática , Camundongos , Camundongos Nus , Mutação , Proteínas de Neoplasias/antagonistas & inibidores , Proteínas de Neoplasias/imunologia , Malformações do Sistema Nervoso/imunologia , Malformações do Sistema Nervoso/mortalidade , Malformações do Sistema Nervoso/patologia , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/imunologia , Ribonuclease H/antagonistas & inibidores , Ribonuclease H/imunologia , Análise de Sequência de RNA , Transdução de Sinais , Análise de Sobrevida , Linfócitos T/imunologia , Linfócitos T/patologiaRESUMO
Ribosome biogenesis is essential for cell growth and proliferation and is commonly elevated in cancer. Accordingly, numerous oncogene and tumor suppressor signaling pathways target rRNA synthesis. In breast cancer, non-canonical Wnt signaling by Wnt5a has been reported to antagonize tumor growth. Here, we show that Wnt5a rapidly represses rDNA gene transcription in breast cancer cells and generates a chromatin state with reduced transcription of rDNA by RNA polymerase I (Pol I). These effects were specifically dependent on Dishevelled1 (DVL1), which accumulates in nucleolar organizer regions (NORs) and binds to rDNA regions of the chromosome. Upon DVL1 binding, the Pol I transcription activator and deacetylase Sirtuin 7 (SIRT7) releases from rDNA loci, concomitant with disassembly of Pol I transcription machinery at the rDNA promoter. These findings reveal that Wnt5a signals through DVL1 to suppress rRNA transcription. This provides a novel mechanism for how Wnt5a exerts tumor suppressive effects and why disruption of Wnt5a signaling enhances mammary tumor growth in vivo.
Assuntos
Neoplasias da Mama/genética , Proteínas Desgrenhadas/genética , RNA Polimerase I/genética , Transcrição Gênica , Proteína Wnt-5a/genética , Neoplasias da Mama/patologia , Cromatina/genética , DNA Ribossômico/genética , Proteínas Desgrenhadas/metabolismo , Regulação Neoplásica da Expressão Gênica , Humanos , Células MCF-7 , Região Organizadora do Nucléolo/genética , Regiões Promotoras Genéticas , Ligação Proteica , RNA Ribossômico/genética , Sirtuínas/genética , Via de Sinalização Wnt/genética , Proteína Wnt-5a/metabolismoRESUMO
Ribosome biogenesis is a canonical hallmark of cell growth and proliferation. Here we show that execution of Epithelial-to-Mesenchymal Transition (EMT), a migratory cellular program associated with development and tumor metastasis, is fueled by upregulation of ribosome biogenesis during G1/S arrest. This unexpected EMT feature is independent of species and initiating signal, and is accompanied by release of the repressive nucleolar chromatin remodeling complex (NoRC) from rDNA, together with recruitment of the EMT-driving transcription factor Snai1 (Snail1), RNA Polymerase I (Pol I) and the Upstream Binding Factor (UBF). EMT-associated ribosome biogenesis is also coincident with increased nucleolar recruitment of Rictor, an essential component of the EMT-promoting mammalian target of rapamycin complex 2 (mTORC2). Inhibition of rRNA synthesis in vivo differentiates primary tumors to a benign, Estrogen Receptor-alpha (ERα) positive, Rictor-negative phenotype and reduces metastasis. These findings implicate the EMT-associated ribosome biogenesis program with cellular plasticity, de-differentiation, cancer progression and metastatic disease.
Assuntos
Transição Epitelial-Mesenquimal/fisiologia , Pontos de Checagem da Fase G1 do Ciclo Celular/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Regulação Neoplásica da Expressão Gênica , Ribossomos/metabolismo , Animais , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Diferenciação Celular/fisiologia , Linhagem Celular Tumoral/transplante , Movimento Celular/fisiologia , Nucléolo Celular/metabolismo , Embrião de Galinha , Proteínas Cromossômicas não Histona/metabolismo , DNA Ribossômico/metabolismo , Modelos Animais de Doenças , Feminino , Perfilação da Expressão Gênica , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , RNA Ribossômico/metabolismo , Ribossomos/genéticaRESUMO
The ribosome, the integration point for protein synthesis in the cell, is conventionally considered a homogeneous molecular assembly that only passively contributes to gene expression. Yet, epigenetic features of the ribosomal DNA (rDNA) operon and changes in the ribosome's molecular composition have been associated with disease phenotypes, suggesting that the ribosome itself may possess inherent regulatory capacity. Analyzing whole-genome sequencing data from the 1000 Genomes Project and the Mouse Genomes Project, we find that rDNA copy number varies widely across individuals, and we identify pervasive intra- and interindividual nucleotide variation in the 5S, 5.8S, 18S, and 28S ribosomal RNA (rRNA) genes of both human and mouse. Conserved rRNA sequence heterogeneities map to functional centers of the assembled ribosome, variant rRNA alleles exhibit tissue-specific expression, and ribosomes bearing variant rRNA alleles are present in the actively translating ribosome pool. These findings provide a critical framework for exploring the possibility that the expression of genomically encoded variant rRNA alleles gives rise to physically and functionally heterogeneous ribosomes that contribute to mammalian physiology and human disease.
Assuntos
Alelos , Regulação da Expressão Gênica , Mutação/genética , Especificidade de Órgãos/genética , RNA Ribossômico/genética , Animais , Sequência de Bases , Cromossomos Humanos/genética , Sequência Conservada/genética , DNA Ribossômico/genética , Evolução Molecular , Dosagem de Genes , Perfilação da Expressão Gênica , Genoma Humano , Células HEK293 , Humanos , Camundongos , Óperon/genética , Biossíntese de Proteínas , Subunidades Proteicas/genética , Processamento Pós-Transcricional do RNA/genética , Ribossomos/metabolismoRESUMO
Escherichia coli strain MRE600 was originally identified for its low RNase I activity and has therefore been widely adopted by the biomedical research community as a preferred source for the expression and purification of transfer RNAs and ribosomes. Despite its widespread use, surprisingly little information about its genome or genetic content exists. Here, we present the first de novo assembly and description of the MRE600 genome and epigenome. To provide context to these studies of MRE600, we include comparative analyses with E. coli K-12 MG1655 (K12). Pacific Biosciences Single Molecule, Real-Time sequencing reads were assembled into one large chromosome (4.83 Mb) and three smaller plasmids (89.1, 56.9, and 7.1 kb). Interestingly, the 7.1-kb plasmid possesses genes encoding a colicin E1 protein and its associated immunity protein. The MRE600 genome has a G + C content of 50.8% and contains a total of 5,181 genes, including 4,913 protein-encoding genes and 268 RNA genes. We identified 41,469 modified DNA bases (0.83% of total) and found that MRE600 lacks the gene for type I methyltransferase, EcoKI. Phylogenetic, taxonomic, and genetic analyses demonstrate that MRE600 is a divergent E. coli strain that displays features of the closely related genus, Shigella. Nevertheless, comparative analyses between MRE600 and E. coli K12 show that these two strains exhibit nearly identical ribosomal proteins, ribosomal RNAs, and highly homologous tRNA species. Substantiating prior suggestions that MRE600 lacks RNase I activity, the RNase I-encoding gene, rna, contains a single premature stop codon early in its open-reading frame.