Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 622
Filtrar
1.
Cell ; 182(6): 1560-1573.e13, 2020 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-32783916

RESUMO

SARS-CoV-2 is the causative agent of the 2019-2020 pandemic. The SARS-CoV-2 genome is replicated and transcribed by the RNA-dependent RNA polymerase holoenzyme (subunits nsp7/nsp82/nsp12) along with a cast of accessory factors. One of these factors is the nsp13 helicase. Both the holo-RdRp and nsp13 are essential for viral replication and are targets for treating the disease COVID-19. Here we present cryoelectron microscopic structures of the SARS-CoV-2 holo-RdRp with an RNA template product in complex with two molecules of the nsp13 helicase. The Nidovirales order-specific N-terminal domains of each nsp13 interact with the N-terminal extension of each copy of nsp8. One nsp13 also contacts the nsp12 thumb. The structure places the nucleic acid-binding ATPase domains of the helicase directly in front of the replicating-transcribing holo-RdRp, constraining models for nsp13 function. We also observe ADP-Mg2+ bound in the nsp12 N-terminal nidovirus RdRp-associated nucleotidyltransferase domain, detailing a new pocket for anti-viral therapy development.


Assuntos
Metiltransferases/química , RNA Helicases/química , RNA Polimerase Dependente de RNA/química , Proteínas não Estruturais Virais/química , Replicação Viral , Difosfato de Adenosina/química , Difosfato de Adenosina/metabolismo , Betacoronavirus/genética , Betacoronavirus/metabolismo , Betacoronavirus/ultraestrutura , Sítios de Ligação , RNA-Polimerase RNA-Dependente de Coronavírus , Microscopia Crioeletrônica , Holoenzimas/química , Holoenzimas/metabolismo , Magnésio/metabolismo , Metiltransferases/metabolismo , Ligação Proteica , RNA Helicases/metabolismo , RNA Viral/química , RNA Polimerase Dependente de RNA/metabolismo , SARS-CoV-2 , Proteínas não Estruturais Virais/metabolismo
2.
Nat Immunol ; 19(1): 76-84, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29180808

RESUMO

Exciting progress in the field of cancer immunotherapy has renewed the urgency of the need for basic studies of immunoregulation in both adaptive cell lineages and innate cell lineages. Here we found a central role for major histocompatibility complex (MHC) class I in controlling the phagocytic function of macrophages. Our results demonstrated that expression of the common MHC class I component ß2-microglobulin (ß2M) by cancer cells directly protected them from phagocytosis. We further showed that this protection was mediated by the inhibitory receptor LILRB1, whose expression was upregulated on the surface of macrophages, including tumor-associated macrophages. Disruption of either MHC class I or LILRB1 potentiated phagocytosis of tumor cells both in vitro and in vivo, which defines the MHC class I-LILRB1 signaling axis as an important regulator of the effector function of innate immune cells, a potential biomarker for therapeutic response to agents directed against the signal-regulatory protein CD47 and a potential target of anti-cancer immunotherapy.


Assuntos
Antígenos de Histocompatibilidade Classe I/imunologia , Receptor B1 de Leucócitos Semelhante a Imunoglobulina/imunologia , Macrófagos/imunologia , Neoplasias/imunologia , Fagocitose/imunologia , Animais , Linhagem Celular Tumoral , Antígenos de Histocompatibilidade Classe I/metabolismo , Humanos , Imunoterapia/métodos , Receptor B1 de Leucócitos Semelhante a Imunoglobulina/metabolismo , Macrófagos/metabolismo , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos NOD , Camundongos Knockout , Camundongos SCID , Neoplasias/metabolismo , Neoplasias/terapia , Neoplasias Experimentais/imunologia , Neoplasias Experimentais/metabolismo , Neoplasias Experimentais/terapia
3.
Cell ; 160(1-2): 285-98, 2015 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-25594184

RESUMO

How are skeletal tissues derived from skeletal stem cells? Here, we map bone, cartilage, and stromal development from a population of highly pure, postnatal skeletal stem cells (mouse skeletal stem cells, mSSCs) to their downstream progenitors of bone, cartilage, and stromal tissue. We then investigated the transcriptome of the stem/progenitor cells for unique gene-expression patterns that would indicate potential regulators of mSSC lineage commitment. We demonstrate that mSSC niche factors can be potent inducers of osteogenesis, and several specific combinations of recombinant mSSC niche factors can activate mSSC genetic programs in situ, even in nonskeletal tissues, resulting in de novo formation of cartilage or bone and bone marrow stroma. Inducing mSSC formation with soluble factors and subsequently regulating the mSSC niche to specify its differentiation toward bone, cartilage, or stromal cells could represent a paradigm shift in the therapeutic regeneration of skeletal tissues.


Assuntos
Osso e Ossos/citologia , Células-Tronco Mesenquimais/citologia , Animais , Proteínas Morfogenéticas Ósseas/metabolismo , Cartilagem/citologia , Linhagem da Célula , Cruzamentos Genéticos , Células-Tronco Mesenquimais/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Transdução de Sinais
4.
Cell ; 159(2): 402-14, 2014 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-25303533

RESUMO

Identification of driver mutations in human diseases is often limited by cohort size and availability of appropriate statistical models. We propose a framework for the systematic discovery of genetic alterations that are causal determinants of disease, by prioritizing genes upstream of functional disease drivers, within regulatory networks inferred de novo from experimental data. We tested this framework by identifying the genetic determinants of the mesenchymal subtype of glioblastoma. Our analysis uncovered KLHL9 deletions as upstream activators of two previously established master regulators of the subtype, C/EBPß and C/EBPδ. Rescue of KLHL9 expression induced proteasomal degradation of C/EBP proteins, abrogated the mesenchymal signature, and reduced tumor viability in vitro and in vivo. Deletions of KLHL9 were confirmed in > 50% of mesenchymal cases in an independent cohort, thus representing the most frequent genetic determinant of the subtype. The method generalized to study other human diseases, including breast cancer and Alzheimer's disease.


Assuntos
Algoritmos , Redes Reguladoras de Genes , Glioblastoma/genética , Mutação , Doença de Alzheimer/genética , Animais , Neoplasias da Mama/genética , Proteína delta de Ligação ao Facilitador CCAAT/metabolismo , Variações do Número de Cópias de DNA , Glioblastoma/patologia , Xenoenxertos , Humanos , Camundongos , Transplante de Neoplasias , Complexo de Endopeptidases do Proteassoma/metabolismo , Proteínas/metabolismo , Locos de Características Quantitativas , Ubiquitinação
5.
Nature ; 620(7973): 445-452, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37495693

RESUMO

To replicate inside macrophages and cause tuberculosis, Mycobacterium tuberculosis must scavenge a variety of nutrients from the host1,2. The mammalian cell entry (MCE) proteins are important virulence factors in M. tuberculosis1,3, where they are encoded by large gene clusters and have been implicated in the transport of fatty acids4-7 and cholesterol1,4,8 across the impermeable mycobacterial cell envelope. Very little is known about how cargos are transported across this barrier, and it remains unclear how the approximately ten proteins encoded by a mycobacterial mce gene cluster assemble to transport cargo across the cell envelope. Here we report the cryo-electron microscopy (cryo-EM) structure of the endogenous Mce1 lipid-import machine of Mycobacterium smegmatis-a non-pathogenic relative of M. tuberculosis. The structure reveals how the proteins of the Mce1 system assemble to form an elongated ABC transporter complex that is long enough to span the cell envelope. The Mce1 complex is dominated by a curved, needle-like domain that appears to be unrelated to previously described protein structures, and creates a protected hydrophobic pathway for lipid transport across the periplasm. Our structural data revealed the presence of a subunit of the Mce1 complex, which we identified using a combination of cryo-EM and AlphaFold2, and name LucB. Our data lead to a structural model for Mce1-mediated lipid import across the mycobacterial cell envelope.


Assuntos
Proteínas de Bactérias , Microscopia Crioeletrônica , Lipídeos , Proteínas de Membrana Transportadoras , Mycobacterium tuberculosis , Internalização do Vírus , Animais , Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Proteínas de Bactérias/ultraestrutura , Proteínas de Membrana Transportadoras/química , Proteínas de Membrana Transportadoras/metabolismo , Proteínas de Membrana Transportadoras/ultraestrutura , Mycobacterium tuberculosis/química , Mycobacterium tuberculosis/metabolismo , Mycobacterium tuberculosis/ultraestrutura , Tuberculose/microbiologia , Fatores de Virulência/química , Fatores de Virulência/metabolismo , Transportadores de Cassetes de Ligação de ATP/química , Transportadores de Cassetes de Ligação de ATP/metabolismo , Transportadores de Cassetes de Ligação de ATP/ultraestrutura , Periplasma/metabolismo , Domínios Proteicos , Interações Hidrofóbicas e Hidrofílicas , Complexos Multiproteicos/química , Complexos Multiproteicos/metabolismo , Complexos Multiproteicos/ultraestrutura
6.
Nature ; 614(7949): 781-787, 2023 02.
Artigo em Inglês | MEDLINE | ID: mdl-36725929

RESUMO

The SARS-CoV-2 RNA-dependent RNA polymerase coordinates viral RNA synthesis as part of an assembly known as the replication-transcription complex (RTC)1. Accordingly, the RTC is a target for clinically approved antiviral nucleoside analogues, including remdesivir2. Faithful synthesis of viral RNAs by the RTC requires recognition of the correct nucleotide triphosphate (NTP) for incorporation into the nascent RNA. To be effective inhibitors, antiviral nucleoside analogues must compete with the natural NTPs for incorporation. How the SARS-CoV-2 RTC discriminates between the natural NTPs, and how antiviral nucleoside analogues compete, has not been discerned in detail. Here, we use cryogenic-electron microscopy to visualize the RTC bound to each of the natural NTPs in states poised for incorporation. Furthermore, we investigate the RTC with the active metabolite of remdesivir, remdesivir triphosphate (RDV-TP), highlighting the structural basis for the selective incorporation of RDV-TP over its natural counterpart adenosine triphosphate3,4. Our results explain the suite of interactions required for NTP recognition, informing the rational design of antivirals. Our analysis also yields insights into nucleotide recognition by the nsp12 NiRAN (nidovirus RdRp-associated nucleotidyltransferase), an enigmatic catalytic domain essential for viral propagation5. The NiRAN selectively binds guanosine triphosphate, strengthening proposals for the role of this domain in the formation of the 5' RNA cap6.


Assuntos
RNA-Polimerase RNA-Dependente de Coronavírus , Microscopia Crioeletrônica , SARS-CoV-2 , Humanos , Antivirais/química , Antivirais/metabolismo , Antivirais/farmacologia , RNA-Polimerase RNA-Dependente de Coronavírus/química , RNA-Polimerase RNA-Dependente de Coronavírus/metabolismo , RNA-Polimerase RNA-Dependente de Coronavírus/ultraestrutura , COVID-19/virologia , Nucleosídeos/metabolismo , Nucleosídeos/farmacologia , RNA Viral/biossíntese , RNA Viral/química , RNA Viral/metabolismo , SARS-CoV-2/enzimologia , Especificidade por Substrato , Guanosina Trifosfato/metabolismo , Capuzes de RNA
7.
Nature ; 604(7906): 541-545, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-35388215

RESUMO

Fidaxomicin (Fdx) is widely used to treat Clostridioides difficile (Cdiff) infections, but the molecular basis of its narrow-spectrum activity in the human gut microbiome remains unknown. Cdiff infections are a leading cause of nosocomial deaths1. Fidaxomicin, which inhibits RNA polymerase, targets Cdiff with minimal effects on gut commensals, reducing recurrence of Cdiff infection2,3. Here we present the cryo-electron microscopy structure of Cdiff RNA polymerase in complex with fidaxomicin and identify a crucial fidaxomicin-binding determinant of Cdiff RNA polymerase that is absent in most gut microbiota such as Proteobacteria and Bacteroidetes. By combining structural, biochemical, genetic and bioinformatic analyses, we establish that a single residue in Cdiff RNA polymerase is a sensitizing element for fidaxomicin narrow-spectrum activity. Our results provide a blueprint for targeted drug design against an important human pathogen.


Assuntos
Clostridioides difficile , Infecções por Clostridium , Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Clostridioides , Infecções por Clostridium/tratamento farmacológico , Infecções por Clostridium/microbiologia , Microscopia Crioeletrônica , RNA Polimerases Dirigidas por DNA , Fidaxomicina/química , Fidaxomicina/farmacologia , Fidaxomicina/uso terapêutico , Humanos
8.
Mol Cell ; 78(2): 275-288.e6, 2020 04 16.
Artigo em Inglês | MEDLINE | ID: mdl-32160514

RESUMO

Transcription initiation requires formation of the open promoter complex (RPo). To generate RPo, RNA polymerase (RNAP) unwinds the DNA duplex to form the transcription bubble and loads the DNA into the RNAP active site. RPo formation is a multi-step process with transient intermediates of unknown structure. We use single-particle cryoelectron microscopy to visualize seven intermediates containing Escherichia coli RNAP with the transcription factor TraR en route to forming RPo. The structures span the RPo formation pathway from initial recognition of the duplex promoter in a closed complex to the final RPo. The structures and supporting biochemical data define RNAP and promoter DNA conformational changes that delineate steps on the pathway, including previously undetected transient promoter-RNAP interactions that contribute to populating the intermediates but do not occur in RPo. Our work provides a structural basis for understanding RPo formation and its regulation, a major checkpoint in gene expression throughout evolution.


Assuntos
RNA Polimerases Dirigidas por DNA/genética , Regiões Promotoras Genéticas/genética , RNA Bacteriano/genética , Iniciação da Transcrição Genética , Microscopia Crioeletrônica , RNA Polimerases Dirigidas por DNA/química , Escherichia coli/genética , Conformação de Ácido Nucleico , Ligação Proteica/genética , Conformação Proteica
9.
EMBO J ; 42(15): e114912, 2023 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-37435707

RESUMO

The diarylquinoline bedaquiline (BDQ) is an FDA-approved drug for the treatment of multidrug-resistant tuberculosis that targets the mycobacterial adenosine triphosphate (ATP) synthase, a key enzyme in cellular respiration. In a recent study, Courbon et al (2023) examine the interaction between Mycobacterium smegmatis ATP synthase with the second generation diarylquinoline TBAJ-876 and the squaramide inhibitor SQ31f, showing that both drugs prevent the rotatory motions needed for enzymatic function.


Assuntos
Diarilquinolinas , Mycobacterium tuberculosis , Diarilquinolinas/farmacologia , Diarilquinolinas/uso terapêutico , Antituberculosos/farmacologia , Antituberculosos/uso terapêutico , Trifosfato de Adenosina
10.
N Engl J Med ; 389(10): 911-921, 2023 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-37672694

RESUMO

BACKGROUND: Alveolar soft part sarcoma (ASPS) is a rare soft-tissue sarcoma with a poor prognosis and no established therapy. Recently, encouraging responses to immune checkpoint inhibitors have been reported. METHODS: We conducted an investigator-initiated, multicenter, single-group, phase 2 study of the anti-programmed death ligand 1 (PD-L1) agent atezolizumab in adult and pediatric patients with advanced ASPS. Atezolizumab was administered intravenously at a dose of 1200 mg (in patients ≥18 years of age) or 15 mg per kilogram of body weight with a 1200-mg cap (in patients <18 years of age) once every 21 days. Study end points included objective response, duration of response, and progression-free survival according to Response Evaluation Criteria in Solid Tumors (RECIST), version 1.1, as well as pharmacodynamic biomarkers of multistep drug action. RESULTS: A total of 52 patients were evaluated. An objective response was observed in 19 of 52 patients (37%), with 1 complete response and 18 partial responses. The median time to response was 3.6 months (range, 2.1 to 19.1), the median duration of response was 24.7 months (range, 4.1 to 55.8), and the median progression-free survival was 20.8 months. Seven patients took a treatment break after 2 years of treatment, and their responses were maintained through the data-cutoff date. No treatment-related grade 4 or 5 adverse events were recorded. Responses were noted despite variable baseline expression of programmed death 1 and PD-L1. CONCLUSIONS: Atezolizumab was effective at inducing sustained responses in approximately one third of patients with advanced ASPS. (Funded by the National Cancer Institute and others; ClinicalTrials.gov number, NCT03141684.).


Assuntos
Anticorpos Monoclonais Humanizados , Antígeno B7-H1 , Sarcoma Alveolar de Partes Moles , Adolescente , Adulto , Criança , Humanos , Recém-Nascido , Anticorpos Monoclonais Humanizados/administração & dosagem , Anticorpos Monoclonais Humanizados/efeitos adversos , Anticorpos Monoclonais Humanizados/uso terapêutico , Antígeno B7-H1/antagonistas & inibidores , Peso Corporal , Sarcoma Alveolar de Partes Moles/tratamento farmacológico , Administração Intravenosa
11.
Nat Chem Biol ; 2024 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-38514884

RESUMO

Protein ubiquitylation controls diverse processes within eukaryotic cells, including protein degradation, and is often dysregulated in disease. Moreover, small-molecule degraders that redirect ubiquitylation activities toward disease targets are an emerging and promising therapeutic class. Over 600 E3 ubiquitin ligases are expressed in humans, but their substrates remain largely elusive, necessitating the development of new methods for their discovery. Here we report the development of E3-substrate tagging by ubiquitin biotinylation (E-STUB), a ubiquitin-specific proximity labeling method that biotinylates ubiquitylated substrates in proximity to an E3 ligase of interest. E-STUB accurately identifies the direct ubiquitylated targets of protein degraders, including collateral targets and ubiquitylation events that do not lead to substrate degradation. It also detects known substrates of E3 ligase CRBN and VHL with high specificity. With the ability to elucidate proximal ubiquitylation events, E-STUB may facilitate the development of proximity-inducing therapeutics and act as a generalizable method for E3-substrate mapping.

13.
Mol Cell ; 69(5): 816-827.e4, 2018 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-29499136

RESUMO

Transcriptional pausing by RNA polymerases (RNAPs) is a key mechanism to regulate gene expression in all kingdoms of life and is a prerequisite for transcription termination. The essential bacterial transcription factor NusA stimulates both pausing and termination of transcription, thus playing a central role. Here, we report single-particle electron cryo-microscopy reconstructions of NusA bound to paused E. coli RNAP elongation complexes with and without a pause-enhancing hairpin in the RNA exit channel. The structures reveal four interactions between NusA and RNAP that suggest how NusA stimulates RNA folding, pausing, and termination. An asymmetric translocation intermediate of RNA and DNA converts the active site of the enzyme into an inactive state, providing a structural explanation for the inhibition of catalysis. Comparing RNAP at different stages of pausing provides insights on the dynamic nature of the process and the role of NusA as a regulatory factor.


Assuntos
RNA Polimerases Dirigidas por DNA , Proteínas de Escherichia coli , Escherichia coli , Dobramento de RNA , RNA Bacteriano , Terminação da Transcrição Genética , Fatores de Elongação da Transcrição , Domínio Catalítico , DNA Bacteriano/química , DNA Bacteriano/metabolismo , RNA Polimerases Dirigidas por DNA/química , RNA Polimerases Dirigidas por DNA/metabolismo , Escherichia coli/química , Escherichia coli/metabolismo , Proteínas de Escherichia coli/química , Proteínas de Escherichia coli/metabolismo , RNA Bacteriano/biossíntese , RNA Bacteriano/química , Fatores de Elongação da Transcrição/química , Fatores de Elongação da Transcrição/metabolismo
14.
Proc Natl Acad Sci U S A ; 120(8): e2215945120, 2023 02 21.
Artigo em Inglês | MEDLINE | ID: mdl-36795753

RESUMO

Transcriptional pausing underpins the regulation of cellular RNA synthesis, but its mechanism remains incompletely understood. Sequence-specific interactions of DNA and RNA with the dynamic, multidomain RNA polymerase (RNAP) trigger reversible conformational changes at pause sites that temporarily interrupt the nucleotide addition cycle. These interactions initially rearrange the elongation complex (EC) into an elemental paused EC (ePEC). ePECs can form longer-lived PECs by further rearrangements or interactions of diffusible regulators. For both bacterial and mammalian RNAPs, a half-translocated state in which the next DNA template base fails to load into the active site appears central to the ePEC. Some RNAPs also swivel interconnected modules that may stabilize the ePEC. However, it is unclear whether swiveling and half-translocation are requisite features of a single ePEC state or if multiple ePEC states exist. Here, we use cryo-electron microscopy (cryo-EM) analysis of ePECs with different RNA-DNA sequences combined with biochemical probes of ePEC structure to define an interconverting ensemble of ePEC states. ePECs occupy either pre- or half-translocated states but do not always swivel, indicating that difficulty in forming the posttranslocated state at certain RNA-DNA sequences may be the essence of the ePEC. The existence of multiple ePEC conformations has broad implications for transcriptional regulation.


Assuntos
RNA Polimerases Dirigidas por DNA , RNA , Microscopia Crioeletrônica , RNA Polimerases Dirigidas por DNA/metabolismo , RNA/genética , DNA , Nucleotídeos/química , Transcrição Gênica
15.
Proc Natl Acad Sci U S A ; 120(14): e2220874120, 2023 04 04.
Artigo em Inglês | MEDLINE | ID: mdl-36972428

RESUMO

Bacterial transcription initiation requires σ factors for nucleation of the transcription bubble. The canonical housekeeping σ factor, σ70, nucleates DNA melting via recognition of conserved bases of the promoter -10 motif, which are unstacked and captured in pockets of σ70. By contrast, the mechanism of transcription bubble nucleation and formation during the unrelated σN-mediated transcription initiation is poorly understood. Herein, we combine structural and biochemical approaches to establish that σN, like σ70, captures a flipped, unstacked base in a pocket formed between its N-terminal region I (RI) and extra-long helix features. Strikingly, RI inserts into the nascent bubble to stabilize the nucleated bubble prior to engagement of the obligate ATPase activator. Our data suggest a general paradigm of transcription initiation that requires σ factors to nucleate an early melted intermediate prior to productive RNA synthesis.


Assuntos
Escherichia coli , Iniciação da Transcrição Genética , Escherichia coli/química , Escherichia coli/metabolismo , RNA Polimerase Sigma 54/química , Fator sigma/química , Regiões Promotoras Genéticas , Microscopia Crioeletrônica
16.
Nature ; 565(7739): 382-385, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30626968

RESUMO

A key regulated step of transcription is promoter melting by RNA polymerase (RNAP) to form the open promoter complex1-3. To generate the open complex, the conserved catalytic core of the RNAP combines with initiation factors to locate promoter DNA, unwind 12-14 base pairs of the DNA duplex and load the template-strand DNA into the RNAP active site. Formation of the open complex is a multi-step process during which transient intermediates of unknown structure are formed4-6. Here we present cryo-electron microscopy structures of bacterial RNAP-promoter DNA complexes, including structures of partially melted intermediates. The structures show that late steps of promoter melting occur within the RNAP cleft, delineate key roles for fork-loop 2 and switch 2-universal structural features of RNAP-in restricting access of DNA to the RNAP active site, and explain why clamp opening is required to allow entry of single-stranded template DNA into the active site. The key roles of fork-loop 2 and switch 2 suggest a common mechanism for late steps in promoter DNA opening to enable gene expression across all domains of life.


Assuntos
Microscopia Crioeletrônica , DNA Bacteriano/química , DNA Bacteriano/ultraestrutura , RNA Polimerases Dirigidas por DNA/metabolismo , Mycobacterium tuberculosis/enzimologia , Conformação de Ácido Nucleico , Regiões Promotoras Genéticas , Proteínas de Bactérias/metabolismo , Sequência de Bases , Domínio Catalítico , DNA Bacteriano/metabolismo , Estabilidade Enzimática/efeitos dos fármacos , Escherichia coli/enzimologia , Lactonas/farmacologia , Modelos Moleculares , Mycobacterium tuberculosis/metabolismo , Desnaturação de Ácido Nucleico , Ligação Proteica , Termodinâmica , Iniciação da Transcrição Genética/efeitos dos fármacos
17.
Mol Cell ; 68(2): 388-397.e6, 2017 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-28988932

RESUMO

Noncoding RNAs (ncRNAs) regulate gene expression in all organisms. Bacterial 6S RNAs globally regulate transcription by binding RNA polymerase (RNAP) holoenzyme and competing with promoter DNA. Escherichia coli (Eco) 6S RNA interacts specifically with the housekeeping σ70-holoenzyme (Eσ70) and plays a key role in the transcriptional reprogramming upon shifts between exponential and stationary phase. Inhibition is relieved upon 6S RNA-templated RNA synthesis. We report here the 3.8 Å resolution structure of a complex between 6S RNA and Eσ70 determined by single-particle cryo-electron microscopy and validation of the structure using footprinting and crosslinking approaches. Duplex RNA segments have A-form C3' endo sugar puckers but widened major groove widths, giving the RNA an overall architecture that mimics B-form promoter DNA. Our results help explain the specificity of Eco 6S RNA for Eσ70 and show how an ncRNA can mimic B-form DNA to directly regulate transcription by the DNA-dependent RNAP.


Assuntos
DNA de Forma B/metabolismo , DNA Bacteriano/metabolismo , RNA Polimerases Dirigidas por DNA/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , RNA Bacteriano/metabolismo , RNA não Traduzido/metabolismo , Fator sigma/metabolismo , DNA de Forma B/genética , DNA Bacteriano/genética , RNA Polimerases Dirigidas por DNA/genética , Escherichia coli/genética , Proteínas de Escherichia coli/genética , RNA Bacteriano/genética , RNA não Traduzido/genética , Fator sigma/genética
18.
Nat Chem Biol ; 18(10): 1065-1075, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35788181

RESUMO

Aldehyde dehydrogenases (ALDHs) are promising cancer drug targets, as certain isoforms are required for the survival of stem-like tumor cells. We have discovered selective inhibitors of ALDH1B1, a mitochondrial enzyme that promotes colorectal and pancreatic cancer. We describe bicyclic imidazoliums and guanidines that target the ALDH1B1 active site with comparable molecular interactions and potencies. Both pharmacophores abrogate ALDH1B1 function in cells; however, the guanidines circumvent an off-target mitochondrial toxicity exhibited by the imidazoliums. Our lead isoform-selective guanidinyl antagonists of ALDHs exhibit proteome-wide target specificity, and they selectively block the growth of colon cancer spheroids and organoids. Finally, we have used genetic and chemical perturbations to elucidate the ALDH1B1-dependent transcriptome, which includes genes that regulate mitochondrial metabolism and ribosomal function. Our findings support an essential role for ALDH1B1 in colorectal cancer, provide molecular probes for studying ALDH1B1 functions and yield leads for developing ALDH1B1-targeting therapies.


Assuntos
Neoplasias do Colo , Neoplasias Colorretais , Aldeído Desidrogenase/química , Aldeído Desidrogenase/genética , Aldeído Desidrogenase/metabolismo , Família Aldeído Desidrogenase 1 , Aldeído-Desidrogenase Mitocondrial/genética , Aldeído-Desidrogenase Mitocondrial/metabolismo , Aldeídos , Neoplasias do Colo/patologia , Neoplasias Colorretais/tratamento farmacológico , Neoplasias Colorretais/genética , Guanidinas , Humanos , Sondas Moleculares , Proteoma/genética
19.
World J Urol ; 42(1): 92, 2024 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-38386090

RESUMO

PURPOSE: Malignant ureteric obstruction is a significant management challenge. The failure of ureteric stents often leads to long-term nephrostomy tubes. This is delayed for as long as possible due to its' associated morbidity. Several types of ureteric stents are available, however there is little evidence demonstrating which stents are better for preventing progression to nephrostomy tubes. This study looked to determine whether a new 6 French (Fr) polymer stent, 8Fr polymer stent or metallic stent achieved a longer functional duration once the initial polymer ureteric stent failed. METHODS: A retrospective, longitudinal study was performed at a single tertiary institution. All patients who underwent ureteric stenting with a 6Fr polymer stent for malignancy between 2010 and 2020 were included. Patients were followed up until death with ureteric stent in situ or permanent nephrostomy tube insertion. RESULTS: A total of 46 patients (66 ureters) had ureteric stents inserted for malignancy. From initial ureteric stent failure, 10 stents were changed to a new 6Fr polymer stent, 42 were changed to an 8Fr polymer stent and 14 were changed to a Resonance® 6Fr metallic stent. The Resonance 6Fr metallic stent had the longest median functional duration of 14 months (p = 0.012). CONCLUSION: Resonance® 6Fr metallic stents appear to have a significantly longer functional duration than a new 6Fr polymer stent or 8Fr polymer stent, which may allow patients to enjoy a better quality of life and delay permanent nephrostomy tube insertion.


Assuntos
Neoplasias , Ureter , Obstrução Ureteral , Humanos , Ureter/cirurgia , Obstrução Ureteral/etiologia , Obstrução Ureteral/cirurgia , Estudos Longitudinais , Qualidade de Vida , Estudos Retrospectivos , Stents , Polímeros
20.
J Surg Oncol ; 2024 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-39016208

RESUMO

OBJECTIVE: Breast angiosarcoma is a tumor that can arise as a primary breast tumor or in association with prior radiation therapy. Angiosarcomas are uniquely sensitive to paclitaxel. This study evaluated the impact neoadjuvant paclitaxel (NAC) therapy has on surgical outcomes, tumor recurrence, and survival in breast angiosarcomas. METHODS: Patients with angiosarcoma of the breast, either primary or radiation-associated, were identified from a prospective institutional database. Patients receiving NAC were compared to those treated with upfront surgery. Clinical and pathological variables were compared using Student's t-test or Fisher's exact test, differences in survival were calculated using Kaplan-Meier methods. RESULTS: Twenty-four patients with angiosarcoma of the breast were identified, 10 with primary angiosarcoma and 14 with radiation-associated angiosarcoma. Twelve patients received NAC, 6 of each with primary angiosarcoma or radiation-associated angiosarcoma. Of these 12 patients, 11 had a margin negative resection (91%) of which, nine had a complete pathological response on surgical pathology. Of the 12 surgery-first patients, four (n = 4/12, 33%) had positive surgical margins, two of the four underwent reoperation. With a median follow-up of 16 months, four NAC patients had recurrence (33%) compared to six patients in the surgery-first group (58%) (p = 0.41). While not statistically significant, NAC patients had a 33% less risk of recurring compared to surgery-first patients ([hazard ratio =0.67 (95% confidence interval 0.16-2.72; p = 0.6]). CONCLUSION: NAC for breast angiosarcoma may be associated with high rates of complete pathological response and margin-negative resection. However, this did not impact overall survival. Future prospective control studies and longer follow-up periods are warranted to understand the impact on recurrence and survival.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA