RESUMEN
Pathogenic clostridial species secrete potent toxins that induce severe host tissue damage. Paeniclostridium sordellii lethal toxin (TcsL) causes an almost invariably lethal toxic shock syndrome associated with gynecological infections. TcsL is 87% similar to C. difficile TcdB, which enters host cells via Frizzled receptors in colon epithelium. However, P. sordellii infections target vascular endothelium, suggesting that TcsL exploits another receptor. Here, using CRISPR/Cas9 screening, we establish semaphorins SEMA6A and SEMA6B as TcsL receptors. We demonstrate that recombinant SEMA6A can protect mice from TcsL-induced edema. A 3.3 Å cryo-EM structure shows that TcsL binds SEMA6A with the same region that in TcdB binds structurally unrelated Frizzled. Remarkably, 15 mutations in this evolutionarily divergent surface are sufficient to switch binding specificity of TcsL to that of TcdB. Our findings establish semaphorins as physiologically relevant receptors for TcsL and reveal the molecular basis for the difference in tissue targeting and disease pathogenesis between highly related toxins.
Asunto(s)
Toxinas Bacterianas/metabolismo , Clostridium sordellii/metabolismo , Semaforinas/metabolismo , Animales , Toxinas Bacterianas/química , Toxinas Bacterianas/toxicidad , Sitios de Unión , Sistemas CRISPR-Cas/genética , Línea Celular , Microscopía por Crioelectrón , Edema/patología , Edema/prevención & control , Femenino , Humanos , Pulmón/efectos de los fármacos , Pulmón/patología , Ratones , Ratones Endogámicos C57BL , Simulación de Dinámica Molecular , Mutagénesis Sitio-Dirigida , Unión Proteica , Estructura Terciaria de Proteína , Proteínas Recombinantes/biosíntesis , Proteínas Recombinantes/aislamiento & purificación , Proteínas Recombinantes/uso terapéutico , Semaforinas/química , Semaforinas/genéticaRESUMEN
Efficient targeted control of splicing is a major goal of functional genomics and therapeutic applications. Guide (g)RNA-directed, deactivated (d)Cas CRISPR enzymes fused to splicing effectors represent a promising strategy due to the flexibility of these systems. However, efficient, specific, and generalizable activation of endogenous exons using this approach has not been previously reported. By screening over 300 dCasRx-splicing factor fusion proteins tethered to splicing reporters, we identify dCasRx-RBM25 as a potent activator of exons. Moreover, dCasRx-RBM25 efficiently activates the splicing of â¼90% of targeted endogenous alternative exons and displays high on-target specificity. Using gRNA arrays for combinatorial targeting, we demonstrate that dCasRx-RBM25 enables multiplexed activation and repression of exons. Using this feature, the targeting of neural-regulated exons in Ptpb1 and Puf60 in embryonic stem cells reveals combinatorial effects on downstream alternative splicing events controlled by these factors. Collectively, our results enable versatile, combinatorial exon-resolution functional assays and splicing-directed therapeutic applications.
Asunto(s)
Empalme Alternativo , Sistemas CRISPR-Cas , Exones , Factores de Empalme de ARN , Proteínas de Unión al ARN , Humanos , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Células HEK293 , Factores de Empalme de ARN/genética , Factores de Empalme de ARN/metabolismo , ARN Guía de Sistemas CRISPR-Cas/genética , ARN Guía de Sistemas CRISPR-Cas/metabolismo , Animales , RatonesRESUMEN
14-3-3 proteins are highly conserved regulatory proteins that interact with hundreds of structurally diverse clients and act as central hubs of signaling networks. However, how 14-3-3 paralogs differ in specificity and how they regulate client protein function are not known for most clients. Here, we map the interactomes of all human 14-3-3 paralogs and systematically characterize the effect of disrupting these interactions on client localization. The loss of 14-3-3 binding leads to the coalescence of a large fraction of clients into discrete foci in a client-specific manner, suggesting a central chaperone-like function for 14-3-3 proteins. Congruently, the engraftment of 14-3-3 binding motifs to nonclients can suppress their aggregation or phase separation. Finally, we show that 14-3-3s negatively regulate the localization of the RNA-binding protein SAMD4A to cytoplasmic granules and inhibit its activity as a translational repressor. Our work suggests that 14-3-3s have a more prominent role as chaperone-like molecules than previously thought.
Asunto(s)
Proteínas 14-3-3 , Proteínas HSP90 de Choque Térmico , Humanos , Proteínas 14-3-3/genética , Proteínas 14-3-3/metabolismo , Proteínas HSP90 de Choque Térmico/metabolismo , Chaperonas Moleculares/metabolismo , Unión ProteicaRESUMEN
How disease-associated mutations impair protein activities in the context of biological networks remains mostly undetermined. Although a few renowned alleles are well characterized, functional information is missing for over 100,000 disease-associated variants. Here we functionally profile several thousand missense mutations across a spectrum of Mendelian disorders using various interaction assays. The majority of disease-associated alleles exhibit wild-type chaperone binding profiles, suggesting they preserve protein folding or stability. While common variants from healthy individuals rarely affect interactions, two-thirds of disease-associated alleles perturb protein-protein interactions, with half corresponding to "edgetic" alleles affecting only a subset of interactions while leaving most other interactions unperturbed. With transcription factors, many alleles that leave protein-protein interactions intact affect DNA binding. Different mutations in the same gene leading to different interaction profiles often result in distinct disease phenotypes. Thus disease-associated alleles that perturb distinct protein activities rather than grossly affecting folding and stability are relatively widespread.
Asunto(s)
Enfermedad/genética , Mutación Missense , Mapas de Interacción de Proteínas , Proteínas/genética , Proteínas/metabolismo , Proteínas de Unión al ADN/genética , Proteínas de Unión al ADN/metabolismo , Estudio de Asociación del Genoma Completo , Humanos , Sistemas de Lectura Abierta , Pliegue de Proteína , Estabilidad ProteicaRESUMEN
Targeted protein degradation and stabilization are promising therapeutic modalities because of their potency, versatility and their potential to expand the druggable target space1,2. However, only a few of the hundreds of E3 ligases and deubiquitinases in the human proteome have been harnessed for this purpose, which substantially limits the potential of the approach. Moreover, there may be other protein classes that could be exploited for protein stabilization or degradation3-5, but there are currently no methods that can identify such effector proteins in a scalable and unbiased manner. Here we established a synthetic proteome-scale platform to functionally identify human proteins that can promote the degradation or stabilization of a target protein in a proximity-dependent manner. Our results reveal that the human proteome contains a large cache of effectors of protein stability. The approach further enabled us to comprehensively compare the activities of human E3 ligases and deubiquitinases, identify and characterize non-canonical protein degraders and stabilizers and establish that effectors have vastly different activities against diverse targets. Notably, the top degraders were more potent against multiple therapeutically relevant targets than the currently used E3 ligases cereblon and VHL. Our study provides a functional catalogue of stability effectors for targeted protein degradation and stabilization and highlights the potential of induced proximity screens for the discovery of new proximity-dependent protein modulators.
Asunto(s)
Enzimas Desubicuitinizantes , Estabilidad Proteica , Proteolisis , Proteoma , Proteómica , Ubiquitina-Proteína Ligasas , Humanos , Enzimas Desubicuitinizantes/análisis , Enzimas Desubicuitinizantes/metabolismo , Proteoma/metabolismo , Ubiquitina-Proteína Ligasas/análisis , Ubiquitina-Proteína Ligasas/metabolismo , Especificidad por Sustrato , Quimera Dirigida a la Proteólisis/metabolismo , Proteína Supresora de Tumores del Síndrome de Von Hippel-Lindau/metabolismoRESUMEN
Transcription is orchestrated by thousands of transcription factors (TFs) and chromatin-associated proteins, but how these are causally connected to transcriptional activation is poorly understood. Here, we conduct an unbiased proteome-scale screen to systematically uncover human proteins that activate transcription in a natural chromatin context. By combining interaction proteomics and chemical inhibitors, we delineate the preference of these transcriptional activators for specific co-activators, highlighting how even closely related TFs can function via distinct cofactors. We also identify potent transactivation domains among the hits and use AlphaFold2 to predict and experimentally validate interaction interfaces of two activation domains with BRD4. Finally, we show that many novel activators are partners in fusion events in tumors and functionally characterize a myofibroma-associated fusion between SRF and C3orf62, a potent p300-dependent activator. Our work provides a functional catalog of potent transactivators in the human proteome and a platform for discovering transcriptional regulators at genome scale.
Asunto(s)
Proteoma , Proteómica , Factores de Transcripción/metabolismo , Transcripción Genética , Activación Transcripcional , Animales , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Línea Celular , Regulación Neoplásica de la Expresión Génica , Células HEK293 , Humanos , Péptidos y Proteínas de Señalización Intercelular/genética , Péptidos y Proteínas de Señalización Intercelular/metabolismo , Células K562 , Ratones , Miofibroma/genética , Miofibroma/metabolismo , Células 3T3 NIH , Factor de Respuesta Sérica/genética , Factor de Respuesta Sérica/metabolismo , Factores de Transcripción/genéticaRESUMEN
With the focus on technology for this issue of Molecular Cell, a group of scientists working in different areas of molecular biology provide their perspective on the most recent important technological advance in their field, where the field is lacking, and their wish list for future technology development.
Asunto(s)
Investigación Biomédica/tendencias , Técnicas Genéticas/tendencias , Biología Molecular/tendencias , Animales , Difusión de Innovaciones , HumanosRESUMEN
Chromosomal translocations frequently promote carcinogenesis by producing gain-of-function fusion proteins. Recent studies have identified highly recurrent chromosomal translocations in patients with endometrial stromal sarcomas (ESSs) and ossifying fibromyxoid tumors (OFMTs), leading to an in-frame fusion of PHF1 (PCL1) to six different subunits of the NuA4/TIP60 complex. While NuA4/TIP60 is a coactivator that acetylates chromatin and loads the H2A.Z histone variant, PHF1 is part of the Polycomb repressive complex 2 (PRC2) linked to transcriptional repression of key developmental genes through methylation of histone H3 on lysine 27. In this study, we characterize the fusion protein produced by the EPC1-PHF1 translocation. The chimeric protein assembles a megacomplex harboring both NuA4/TIP60 and PRC2 activities and leads to mislocalization of chromatin marks in the genome, in particular over an entire topologically associating domain including part of the HOXD cluster. This is linked to aberrant gene expression-most notably increased expression of PRC2 target genes. Furthermore, we show that JAZF1-implicated with a PRC2 component in the most frequent translocation in ESSs, JAZF1-SUZ12-is a potent transcription activator that physically associates with NuA4/TIP60, its fusion creating outcomes similar to those of EPC1-PHF1 Importantly, the specific increased expression of PRC2 targets/HOX genes was also confirmed with ESS patient samples. Altogether, these results indicate that most chromosomal translocations linked to these sarcomas use the same molecular oncogenic mechanism through a physical merge of NuA4/TIP60 and PRC2 complexes, leading to mislocalization of histone marks and aberrant Polycomb target gene expression.
Asunto(s)
Neoplasias Endometriales , Sarcoma Estromático Endometrial , Sarcoma , Cromatina , Proteínas de Unión al ADN/metabolismo , Neoplasias Endometriales/genética , Neoplasias Endometriales/metabolismo , Neoplasias Endometriales/patología , Femenino , Histonas/metabolismo , Humanos , Complejo Represivo Polycomb 2/genética , Complejo Represivo Polycomb 2/metabolismo , Proteínas del Grupo Polycomb/genética , Proteínas del Grupo Polycomb/metabolismo , Sarcoma/genética , Sarcoma Estromático Endometrial/genética , Sarcoma Estromático Endometrial/metabolismo , Sarcoma Estromático Endometrial/patología , Translocación Genética/genéticaRESUMEN
Chaperones are abundant cellular proteins that promote the folding and function of their substrate proteins (clients). In vivo, chaperones also associate with a large and diverse set of cofactors (cochaperones) that regulate their specificity and function. However, how these cochaperones regulate protein folding and whether they have chaperone-independent biological functions is largely unknown. We combined mass spectrometry and quantitative high-throughput LUMIER assays to systematically characterize the chaperone-cochaperone-client interaction network in human cells. We uncover hundreds of chaperone clients, delineate their participation in specific cochaperone complexes, and establish a surprisingly distinct network of protein-protein interactions for cochaperones. As a salient example of the power of such analysis, we establish that NUDC family cochaperones specifically associate with structurally related but evolutionarily distinct ß-propeller folds. We provide a framework for deciphering the proteostasis network and its regulation in development and disease and expand the use of chaperones as sensors for drug-target engagement.
Asunto(s)
Proteínas HSP70 de Choque Térmico/metabolismo , Proteínas HSP90 de Choque Térmico/metabolismo , Mapas de Interacción de Proteínas , Humanos , Pliegue de Proteína , Proteínas de Unión a Tacrolimus/metabolismoRESUMEN
Hsp70s comprise a deeply conserved chaperone family that has a central role in maintaining protein homeostasis. In humans, Hsp70 client specificity is provided by 49 different co-factors known as J domain proteins (JDPs). However, the cellular function and client specificity of JDPs have largely remained elusive. We have combined affinity purification-mass spectrometry (AP-MS) and proximity-dependent biotinylation (BioID) to characterize the interactome of all human JDPs and Hsp70s. The resulting network suggests specific functions for many uncharacterized JDPs, and we establish a role of conserved JDPs DNAJC9 and DNAJC27 in histone chaperoning and ciliogenesis, respectively. Unexpectedly, we find that the J domain of DNAJC27 but not of other JDPs can fully replace the function of endogenous DNAJC27, suggesting a previously unappreciated role for J domains themselves in JDP specificity. More broadly, our work expands the role of the Hsp70-regulated proteostasis network and provides a platform for further discovery of JDP-dependent functions.
Asunto(s)
Proteínas del Choque Térmico HSP40/fisiología , Proteínas HSP70 de Choque Térmico/fisiología , Dominios y Motivos de Interacción de Proteínas/fisiología , Células HEK293 , Proteínas del Choque Térmico HSP40/metabolismo , Proteínas HSP70 de Choque Térmico/metabolismo , Células HeLa , Humanos , Chaperonas Moleculares/metabolismo , Unión Proteica , Dominios Proteicos , Proteínas de Unión al GTP rab/metabolismoRESUMEN
Although the proteins that read the gene regulatory code, transcription factors (TFs), have been largely identified, it is not well known which sequences TFs can recognize. We have analyzed the sequence-specific binding of human TFs using high-throughput SELEX and ChIP sequencing. A total of 830 binding profiles were obtained, describing 239 distinctly different binding specificities. The models represent the majority of human TFs, approximately doubling the coverage compared to existing systematic studies. Our results reveal additional specificity determinants for a large number of factors for which a partial specificity was known, including a commonly observed A- or T-rich stretch that flanks the core motifs. Global analysis of the data revealed that homodimer orientation and spacing preferences, and base-stacking interactions, have a larger role in TF-DNA binding than previously appreciated. We further describe a binding model incorporating these features that is required to understand binding of TFs to DNA.
Asunto(s)
Inmunoprecipitación de Cromatina , Modelos Biológicos , Técnica SELEX de Producción de Aptámeros , Factores de Transcripción/metabolismo , Animales , ADN/química , Humanos , Cadenas de Markov , Ratones , Filogenia , Factores de Transcripción/genéticaRESUMEN
HSP90 is a molecular chaperone that associates with numerous substrate proteins called clients. It plays many important roles in human biology and medicine, but determinants of client recognition by HSP90 have remained frustratingly elusive. We systematically and quantitatively surveyed most human kinases, transcription factors, and E3 ligases for interaction with HSP90 and its cochaperone CDC37. Unexpectedly, many more kinases than transcription factors bound HSP90. CDC37 interacted with kinases, but not with transcription factors or E3 ligases. HSP90::kinase interactions varied continuously over a 100-fold range and provided a platform to study client protein recognition. In wild-type clients, HSP90 did not bind particular sequence motifs, but rather associated with intrinsically unstable kinases. Stabilization of the kinase in either its active or inactive conformation with diverse small molecules decreased HSP90 association. Our results establish HSP90 client recognition as a combinatorial process: CDC37 provides recognition of the kinase family, whereas thermodynamic parameters determine client binding within the family.
Asunto(s)
Proteínas HSP90 de Choque Térmico/metabolismo , Mapeo de Interacción de Proteínas , Secuencia de Aminoácidos , Animales , Proteínas de Ciclo Celular/metabolismo , Chaperoninas/metabolismo , Humanos , Luciferasas de Renilla/metabolismo , Modelos Moleculares , Datos de Secuencia Molecular , Dominios y Motivos de Interacción de Proteínas , Proteínas Quinasas/química , Proteínas Quinasas/metabolismo , Estabilidad Proteica , Proteoma/análisis , Receptores de Esteroides/metabolismo , Alineación de Secuencia , Termodinámica , Factores de Transcripción/metabolismo , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
Heat Shock Factor 1 (HSF1) is best known as the master transcriptional regulator of the heat-shock response (HSR), a conserved adaptive mechanism critical for protein homeostasis (proteostasis). Combining a genome-wide RNAi library with an HSR reporter, we identified Jumonji domain-containing protein 6 (JMJD6) as an essential mediator of HSF1 activity. In follow-up studies, we found that JMJD6 is itself a noncanonical transcriptional target of HSF1 which acts as a critical regulator of proteostasis. In a positive feedback circuit, HSF1 binds and promotes JMJD6 expression, which in turn reduces heat shock protein 70 (HSP70) R469 monomethylation to disrupt HSP70-HSF1 repressive complexes resulting in enhanced HSF1 activation. Thus, JMJD6 is intricately wired into the proteostasis network where it plays a critical role in cellular adaptation to proteotoxic stress.
Asunto(s)
Proteínas HSP70 de Choque Térmico , Factores de Transcripción del Choque Térmico , Respuesta al Choque Térmico , Histona Demetilasas con Dominio de Jumonji , Proteostasis , Humanos , Factores de Transcripción del Choque Térmico/metabolismo , Factores de Transcripción del Choque Térmico/genética , Respuesta al Choque Térmico/fisiología , Histona Demetilasas con Dominio de Jumonji/metabolismo , Histona Demetilasas con Dominio de Jumonji/genética , Proteínas HSP70 de Choque Térmico/metabolismo , Proteínas HSP70 de Choque Térmico/genética , Proteostasis/fisiología , Retroalimentación Fisiológica , Adaptación Fisiológica , Células HEK293 , Estrés ProteotóxicoRESUMEN
MRG15/MORF4L1 is a highly conserved protein in eukaryotes that contains a chromodomain (CHD) recognizing methylation of lysine 36 on histone H3 (H3K36me3) in chromatin. Intriguingly, it has been reported in the literature to interact with several different factors involved in chromatin modifications, gene regulation, alternative mRNA splicing, and DNA repair by homologous recombination. To get a complete and reliable picture of associations in physiological conditions, we used genome editing and tandem affinity purification to analyze the stable native interactome of human MRG15, its paralog MRGX/MORF4L2 that lacks the CHD, and MRGBP (MRG-binding protein) in isogenic K562 cells. We found stable interchangeable association of MRG15 and MRGX with the NuA4/TIP60 histone acetyltransferase/chromatin remodeler, Sin3B histone deacetylase/demethylase, ASH1L histone methyltransferase, and PALB2-BRCA2 DNA repair protein complexes. These associations were further confirmed and analyzed by CRISPR tagging of endogenous proteins and comparison of expressed isoforms. Importantly, based on structural information, point mutations could be introduced that specifically disrupt MRG15 association with some complexes but not others. Most interestingly, we also identified a new abundant native complex formed by MRG15/X-MRGBP-BRD8-EP400NL (EP400 N-terminal like) that is functionally similar to the yeast TINTIN (Trimer Independent of NuA4 for Transcription Interactions with Nucleosomes) complex. Our results show that EP400NL, being homologous to the N-terminal region of NuA4/TIP60 subunit EP400, creates TINTIN by competing for BRD8 association. Functional genomics indicate that human TINTIN plays a role in transcription of specific genes. This is most likely linked to the H4ac-binding bromodomain of BRD8 along the H3K36me3-binding CHD of MRG15 on the coding region of transcribed genes. Taken together, our data provide a complete detailed picture of human MRG proteins-associated protein complexes, which are essential to understand and correlate their diverse biological functions in chromatin-based nuclear processes.
Asunto(s)
Factores de Transcripción , Cromatina/metabolismo , Histona Acetiltransferasas/genética , Histona Acetiltransferasas/metabolismo , Histonas/metabolismo , Humanos , Nucleosomas/metabolismo , Factores de Transcripción/metabolismoRESUMEN
Ykt6 is a soluble N-ethylmaleimide sensitive factor activating protein receptor (SNARE) critically involved in diverse vesicular fusion pathways. While most SNAREs rely on transmembrane domains for their activity, Ykt6 dynamically cycles between the cytosol and membrane-bound compartments where it is active. The mechanism that regulates these transitions and allows Ykt6 to achieve specificity toward vesicular pathways is unknown. Using a Parkinson's disease (PD) model, we found that Ykt6 is phosphorylated at an evolutionarily conserved site which is regulated by Ca2+ signaling. Through a multidisciplinary approach, we show that phosphorylation triggers a conformational change that allows Ykt6 to switch from a closed cytosolic to an open membrane-bound form. In the phosphorylated open form, the spectrum of protein interactions changes, leading to defects in both the secretory and autophagy pathways, enhancing toxicity in PD models. Our studies reveal a mechanism by which Ykt6 conformation and activity are regulated with potential implications for PD.
Asunto(s)
Secuencia Conservada , Modelos Moleculares , Conformación Proteica , Proteínas R-SNARE/química , Proteínas R-SNARE/metabolismo , Aminoácidos , Autofagia , Proteínas Portadoras/química , Proteínas Portadoras/metabolismo , Membrana Celular/metabolismo , Evolución Molecular , Fosforilación , Unión Proteica , Dominios y Motivos de Interacción de Proteínas , Proteínas R-SNARE/genética , Relación Estructura-ActividadRESUMEN
Clustered regularly interspaced short palindromic repeat interference (CRISPRi), based on the fusion of inactive Cas9 (dCas9) to the Krüppel-associated box (KRAB) repressor, is a powerful platform for silencing gene expression. However, it suffers from incomplete silencing of target genes. We assayed 57 KRAB domains for their repressive potency and identified the ZIM3 KRAB domain as an exceptionally potent repressor. We establish that ZIM3 KRAB-dCas9 fusion silences gene expression more efficiently than existing platforms.
Asunto(s)
Proteína 9 Asociada a CRISPR/genética , Sistemas CRISPR-Cas/genética , Repeticiones Palindrómicas Cortas Agrupadas y Regularmente Espaciadas , Factores de Transcripción de Tipo Kruppel/genética , Dominio Catalítico , Genes Reporteros , Células HEK293 , Humanos , Células K562 , Regiones Promotoras Genéticas , ARN Guía de Kinetoplastida/genética , Proteínas Represoras/genética , Transcripción GenéticaRESUMEN
BACKGROUND: Healthcare workers frequently face ethically demanding situations in their work, potentially leading to stress of conscience. Long-term work intensification (more and more effort demanded year after year), organizational change and COVID-19 may be risk factors concerning stress of conscience. AIMS: The main aim was to investigate the relationship between long-term work intensification and stress of conscience among the personnel in a healthcare organization. Organizational change management was considered a mediator and COVID-19-related work stress a moderator in the association between work intensification and stress of conscience. RESEARCH DESIGN, PARTICIPANTS AND CONTEXT: A total of 211 healthcare district employees participated in a longitudinal survey using questionnaires collected in 2019 (major organizational change in the planning stage) and 2021 (organizational change completed). ETHICAL CONSIDERATIONS: The study was implemented according to the guidelines of the Finnish National Board on Research Integrity. The Finnish instructions were that no review by an ethics committee was necessary because participation was voluntary, informed consent was requested, participants were assured that they were free to withdraw from the longitudinal study at any time and no health data were collected. FINDINGS: Long-term work intensification was associated with more severe stress of conscience. Long-term work intensification was partially mediated through change management to stress of conscience. High COVID-19 stress strengthened the association between long-term work intensification and stress of conscience. CONCLUSIONS: Long-term work intensification must be addressed to reduce stress of conscience in healthcare, otherwise the healthcare system will be vulnerable to changes and crisis. Extra resources for personnel and management should be allocated because of work intensification during organizational change and health crises like the COVID-19 pandemic to alleviate stress of conscience.
RESUMEN
The RAF family kinases function in the RAS-ERK pathway to transmit signals from activated RAS to the downstream kinases MEK and ERK. This pathway regulates cell proliferation, differentiation and survival, enabling mutations in RAS and RAF to act as potent drivers of human cancers. Drugs targeting the prevalent oncogenic mutant BRAF(V600E) have shown great efficacy in the clinic, but long-term effectiveness is limited by resistance mechanisms that often exploit the dimerization-dependent process by which RAF kinases are activated. Here, we investigated a proteolysis-targeting chimera (PROTAC) approach to BRAF inhibition. The most effective PROTAC, termed P4B, displayed superior specificity and inhibitory properties relative to non-PROTAC controls in BRAF(V600E) cell lines. In addition, P4B displayed utility in cell lines harboring alternative BRAF mutations that impart resistance to conventional BRAF inhibitors. This work provides a proof of concept for a substitute to conventional chemical inhibition to therapeutically constrain oncogenic BRAF.
Asunto(s)
Antineoplásicos , Inhibidores de Proteínas Quinasas , Proteínas Proto-Oncogénicas B-raf , Talidomida , Ubiquitina , Animales , Femenino , Humanos , Ratones , Antineoplásicos/farmacología , Apoptosis/efectos de los fármacos , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Diseño de Fármacos , Resistencia a Antineoplásicos , Quinasas MAP Reguladas por Señal Extracelular/metabolismo , Regulación de la Expresión Génica , Sistema de Señalización de MAP Quinasas , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Modelos Moleculares , Estructura Molecular , Terapia Molecular Dirigida , Mutación , Fosforilación/efectos de los fármacos , Unión Proteica , Inhibidores de Proteínas Quinasas/farmacología , Proteolisis , Proteínas Proto-Oncogénicas B-raf/antagonistas & inhibidores , Proteínas Proto-Oncogénicas B-raf/genética , Transducción de Señal , Relación Estructura-Actividad , Talidomida/análogos & derivados , Talidomida/química , Ubiquitina/químicaRESUMEN
Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone that facilitates the maturation of a wide range of proteins (known as clients). Clients are enriched in signal transducers, including kinases and transcription factors. Therefore, HSP90 regulates diverse cellular functions and exerts marked effects on normal biology, disease and evolutionary processes. Recent structural and functional analyses have provided new insights on the transcriptional and biochemical regulation of HSP90 and the structural dynamics it uses to act on a diverse client repertoire. Comprehensive understanding of how HSP90 functions promises not only to provide new avenues for therapeutic intervention, but to shed light on fundamental biological questions.
Asunto(s)
Proteínas HSP90 de Choque Térmico/metabolismo , Proteínas/metabolismo , Animales , Proteínas HSP90 de Choque Térmico/química , Proteínas HSP90 de Choque Térmico/genética , Humanos , Modelos Biológicos , Chaperonas Moleculares/química , Chaperonas Moleculares/genética , Chaperonas Moleculares/metabolismo , Pliegue de Proteína , Proteínas/química , Proteínas/genéticaRESUMEN
Global repression of protein synthesis is a hallmark of the cellular stress response and has been attributed primarily to inhibition of translation initiation, although this mechanism may not always explain the full extent of repression. Here, using ribosome footprinting, we show that 2 hr of severe heat stress triggers global pausing of translation elongation at around codon 65 on most mRNAs in both mouse and human cells. The genome-wide nature of the phenomenon, its location, and features of protein N termini suggested the involvement of ribosome-associated chaperones. After severe heat shock, Hsp70's interactions with the translational machinery were markedly altered and its association with ribosomes was reduced. Pretreatment with mild heat stress or overexpression of Hsp70 protected cells from heat shock-induced elongation pausing, while inhibition of Hsp70 activity triggered elongation pausing without heat stress. Our findings suggest that regulation of translation elongation in general, and by chaperones in particular, represents a major component of cellular stress responses.