RESUMEN
Gene expression by RNA polymerase II (RNAPII) is tightly controlled by cyclin-dependent kinases (CDKs) at discrete checkpoints during the transcription cycle. The pausing checkpoint following transcription initiation is primarily controlled by CDK9. We discovered that CDK9-mediated, RNAPII-driven transcription is functionally opposed by a protein phosphatase 2A (PP2A) complex that is recruited to transcription sites by the Integrator complex subunit INTS6. PP2A dynamically antagonizes phosphorylation of key CDK9 substrates including DSIF and RNAPII-CTD. Loss of INTS6 results in resistance to tumor cell death mediated by CDK9 inhibition, decreased turnover of CDK9 phospho-substrates, and amplification of acute oncogenic transcriptional responses. Pharmacological PP2A activation synergizes with CDK9 inhibition to kill both leukemic and solid tumor cells, providing therapeutic benefit in vivo. These data demonstrate that fine control of gene expression relies on the balance between kinase and phosphatase activity throughout the transcription cycle, a process dysregulated in cancer that can be exploited therapeutically.
Asunto(s)
Quinasa 9 Dependiente de la Ciclina/metabolismo , Terapia Molecular Dirigida , Neoplasias/tratamiento farmacológico , Neoplasias/genética , Proteína Fosfatasa 2/metabolismo , Proteínas de Unión al ARN/metabolismo , Transcripción Genética , Proteínas Supresoras de Tumor/metabolismo , Animales , Línea Celular Tumoral , Quinasa 9 Dependiente de la Ciclina/antagonistas & inhibidores , Resistencia a Antineoplásicos/genética , Regulación Neoplásica de la Expresión Génica , Humanos , Ratones Endogámicos NOD , Fosforilación , Unión Proteica , ARN Polimerasa II/química , ARN Polimerasa II/metabolismo , Especificidad por SustratoRESUMEN
The Hippo tumor suppressor pathway controls transcription by regulating nuclear abundance of YAP and TAZ, which activate transcription with the TEAD1-TEAD4 DNA-binding proteins. Recently, several small-molecule inhibitors of YAP and TEADs have been reported, with some entering clinical trials for different cancers with Hippo pathway deregulation, most notably, mesothelioma. Using genome-wide CRISPR/Cas9 screens we reveal that mutations in genes from the Hippo, MAPK, and JAK-STAT signaling pathways all modulate the response of mesothelioma cell lines to TEAD palmitoylation inhibitors. By exploring gene expression programs of mutant cells, we find that MAPK pathway hyperactivation confers resistance to TEAD inhibition by reinstating expression of a subset of YAP/TAZ target genes. Consistent with this, combined inhibition of TEAD and the MAPK kinase MEK, synergistically blocks proliferation of multiple mesothelioma and lung cancer cell lines and more potently reduces the growth of patient-derived lung cancer xenografts in vivo. Collectively, we reveal mechanisms by which cells can overcome small-molecule inhibition of TEAD palmitoylation and potential strategies to enhance the anti-tumor activity of emerging Hippo pathway targeted therapies.
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Dedifferentiation is the reversion of mature cells to a stem cell-like fate, whereby gene expression programs are altered and genes associated with multipotency are (re)expressed. Misexpression of multipotency factors and pathways causes the formation of ectopic neural stem cells (NSCs). Whether dedifferentiated NSCs faithfully produce the correct number and types of progeny, or undergo timely terminal differentiation, has not been assessed. Here, we show that ectopic NSCs induced via bHLH transcription factor Deadpan (Dpn) expression fail to undergo appropriate temporal progression by constantly expressing mid-temporal transcription factor(tTF), Sloppy-paired 1/2 (Slp). Consequently, this resulted in impaired terminal differenation and generated an excess of Twin of eyeless (Toy)-positive neurons at the expense of Reversed polarity (Repo)-positive glial cells. Preference for a mid-temporal fate in these ectopic NSCs is concordant with an enriched binding of Dpn at mid-tTF loci and a depletion of Dpn binding at early- and late-tTF loci. Retriggering the temporal series via manipulation of the temporal series or cell cycle is sufficient to reinstate neuronal diversity and timely termination.
Asunto(s)
Proteínas de Drosophila , Células-Madre Neurales , Proteínas de Drosophila/genética , Células-Madre Neurales/metabolismo , Factores de Transcripción/metabolismo , Neuronas/metabolismo , Neuroglía , Diferenciación Celular/genética , Regulación del Desarrollo de la Expresión GénicaRESUMEN
The Hippo pathway is an important regulator of organ growth and cell fate. In the R8 photoreceptor cells of the Drosophila melanogaster eye, the Hippo pathway controls the fate choice between one of two subtypes that express either the blue light-sensitive Rhodopsin 5 (Hippo inactive R8 subtype) or the green light-sensitive Rhodopsin 6 (Hippo active R8 subtype). The degree to which the mechanism of Hippo signal transduction and the proteins that mediate it are conserved in organ growth and R8 cell fate choice is currently unclear. Here, we identify Crumbs and the apical spectrin cytoskeleton as regulators of R8 cell fate. By contrast, other proteins that influence Hippo-dependent organ growth, such as the basolateral spectrin cytoskeleton and Ajuba, are dispensable for the R8 cell fate choice. Surprisingly, Crumbs promotes the Rhodopsin 5 cell fate, which is driven by Yorkie, rather than the Rhodopsin 6 cell fate, which is driven by Warts and the Hippo pathway, which contrasts with its impact on Hippo activity in organ growth. Furthermore, neither the apical spectrin cytoskeleton nor Crumbs appear to regulate the Hippo pathway through mechanisms that have been observed in growing organs. Together, these results show that only a subset of Hippo pathway proteins regulate the R8 binary cell fate decision and that aspects of Hippo signalling differ between growing organs and post-mitotic R8 cells.
Asunto(s)
Linaje de la Célula/fisiología , Proteínas de Drosophila/fisiología , Proteínas del Ojo/fisiología , Ojo/citología , Proteínas de la Membrana/fisiología , Rodopsina/fisiología , Espectrina/fisiología , Animales , Citoesqueleto/fisiología , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Ojo/crecimiento & desarrollo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Células Fotorreceptoras de Invertebrados/fisiología , Proteínas Serina-Treonina Quinasas/metabolismoRESUMEN
The Hippo pathway is a highly conserved signalling pathway that regulates multiple biological processes, including organ size control and cell fate. Since its discovery, genetic and biochemical studies have elucidated several key signalling steps important for pathway activation and deactivation. In recent years, technical advances in microscopy and genome modification have allowed new insights into Hippo signalling to be revealed. These studies have highlighted that the nuclear-cytoplasmic shuttling behaviour of the Hippo pathway transcriptional co-activators Yorkie, YAP and TAZ is far more dynamic than previously appreciated, and YAP and TAZ are also regulated by liquid-liquid phase separation. Here, we review our current understanding of Yorkie, YAP and TAZ regulation, with a focus on recent microscopy-based studies.
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Proteínas Adaptadoras Transductoras de Señales/metabolismo , Regulación del Desarrollo de la Expresión Génica , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de Señal , Transactivadores/metabolismo , Transporte Activo de Núcleo Celular , Animales , Núcleo Celular/metabolismo , Humanos , Proteínas Serina-Treonina Quinasas/química , Transducción de Señal/genética , Transactivadores/químicaRESUMEN
How biochemical and mechanical information are integrated during tissue development is a central question in morphogenesis. In many biological systems, the PIX-GIT complex localises to focal adhesions and integrates both physical and chemical information. We used Drosophila melanogaster egg chamber formation to study the function of PIX and GIT orthologues (dPix and Git, respectively), and discovered a central role for this complex in controlling myosin activity and epithelial monolayering. We found that Git's focal adhesion targeting domain mediates basal localisation of this complex to filament structures and the leading edge of migrating cells. In the absence of dpix and git, tissue disruption is driven by contractile forces, as reduction of myosin activators restores egg production and morphology. Further, dpix and git mutant eggs closely phenocopy defects previously reported in pak mutant epithelia. Together, these results indicate that the dPix-Git complex controls egg chamber morphogenesis by controlling myosin contractility and Pak kinase downstream of focal adhesions.
Asunto(s)
Transportadoras de Casetes de Unión a ATP/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Proteínas Activadoras de GTPasa/genética , Morfogénesis/genética , Miosinas/genética , Transportadoras de Casetes de Unión a ATP/metabolismo , Animales , Movimiento Celular , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citología , Drosophila melanogaster/crecimiento & desarrollo , Drosophila melanogaster/metabolismo , Células Epiteliales/citología , Células Epiteliales/metabolismo , Femenino , Adhesiones Focales/metabolismo , Adhesiones Focales/ultraestructura , Proteínas Activadoras de GTPasa/metabolismo , Perfilación de la Expresión Génica , Regulación del Desarrollo de la Expresión Génica , Mecanotransducción Celular , Miosinas/metabolismo , Cigoto/citología , Cigoto/crecimiento & desarrollo , Cigoto/metabolismo , Quinasas p21 Activadas/genética , Quinasas p21 Activadas/metabolismoRESUMEN
Dendritic arborization is highly regulated and requires tight control of dendritic growth, branching, cytoskeletal dynamics, and ion channel expression to ensure proper function. Abnormal dendritic development can result in altered network connectivity, which has been linked to neurodevelopmental disorders, including autism spectrum disorders (ASDs). How neuronal growth control programs tune dendritic arborization to ensure function is still not fully understood. Using Drosophila dendritic arborization (da) neurons as a model, we identified the conserved Ste20-like kinase Tao as a negative regulator of dendritic arborization. We show that Tao kinase activity regulates cytoskeletal dynamics and sensory channel localization required for proper sensory function in both male and female flies. We further provide evidence for functional conservation of Tao kinase, showing that its ASD-linked human ortholog, Tao kinase 2 (Taok2), could replace Drosophila Tao and rescue dendritic branching, dynamic microtubule alterations, and behavioral defects. However, several ASD-linked Taok2 variants displayed impaired rescue activity, suggesting that Tao/Taok2 mutations can disrupt sensory neuron development and function. Consistently, we show that Tao kinase activity is required in developing and as well as adult stages for maintaining normal dendritic arborization and sensory function to regulate escape and social behavior. Our data suggest an important role for Tao kinase signaling in cytoskeletal organization to maintain proper dendritic arborization and sensory function, providing a strong link between developmental sensory aberrations and behavioral abnormalities relevant for Taok2-dependent ASDs.SIGNIFICANCE STATEMENT Autism spectrum disorders (ASDs) are linked to abnormal dendritic arbors. However, the mechanisms of how dendritic arbors develop to promote functional and proper behavior are unclear. We identified Drosophila Tao kinase, the ortholog of the ASD risk gene Taok2, as a regulator of dendritic arborization in sensory neurons. We show that Tao kinase regulates cytoskeletal dynamics, controls sensory ion channel localization, and is required to maintain somatosensory function in vivo Interestingly, ASD-linked human Taok2 mutations rendered it nonfunctional, whereas its WT form could restore neuronal morphology and function in Drosophila lacking endogenous Tao. Our findings provide evidence for a conserved role of Tao kinase in dendritic development and function of sensory neurons, suggesting that aberrant sensory function might be a common feature of ASDs.
Asunto(s)
Citoesqueleto/fisiología , Dendritas/fisiología , Proteínas de Drosophila/genética , Proteínas de Drosophila/fisiología , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/fisiología , Sensación/fisiología , Actinas/metabolismo , Animales , Animales Modificados Genéticamente , Citoesqueleto/ultraestructura , Dendritas/ultraestructura , Drosophila , Reacción de Fuga , Femenino , Humanos , Masculino , Mecanorreceptores/fisiología , Mutación/genética , Conducta SocialRESUMEN
Metazoans have evolved several pathways to regulate the size of organs and ultimately that of organisms. One such pathway is known as Salvador-Warts-Hippo, or simply Hippo. Research on the Hippo pathway has grown exponentially during the past 8 years, revealing a complex signaling network. Intriguingly, within this complexity, there are levels of modularity. One level of modularity is represented by the unusually wide occurrence of the WW module in the Hippo core kinase cassette, the upstream regulatory components and the downstream nuclear proteins. We suggest that the prevalence of WW domain-mediated complexes in the Hippo pathway should facilitate its molecular analysis and aid prediction of new pathway components.
Asunto(s)
Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de Señal , Animales , Duplicación de Gen , HumanosRESUMEN
The Hippo pathway is an important regulator of organ growth and cell fate. The major mechanism by which Hippo is known to control transcription is by dictating the nucleo-cytoplasmic shuttling rate of Yorkie, a transcription co-activator, which promotes transcription with the DNA binding protein Scalloped. The nuclear biophysical behavior of Yorkie and Scalloped, and whether this is regulated by the Hippo pathway, remains unexplored. Using multiple live-imaging modalities on Drosophila tissues, we found that Scalloped interacts with DNA on a broad range of timescales, and enrichment of Scalloped at sites of active transcription is mediated by longer DNA dwell times. Further, Yorkie increased Scalloped's DNA dwell time, whereas the repressors Nervous fingers 1 (Nerfin-1) and Tondu-domain-containing growth inhibitor (Tgi) decreased it. Therefore, the Hippo pathway influences transcription not only by controlling nuclear abundance of Yorkie but also by modifying the DNA binding kinetics of the transcription factor Scalloped.
Asunto(s)
Cromatina , Proteínas de Drosophila , Drosophila melanogaster , Proteínas Serina-Treonina Quinasas , Transducción de Señal , Transactivadores , Transcripción Genética , Proteínas Señalizadoras YAP , Animales , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Cromatina/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Drosophila melanogaster/metabolismo , Drosophila melanogaster/genética , Proteínas Señalizadoras YAP/metabolismo , Transactivadores/metabolismo , Transactivadores/genética , Factores de Transcripción/metabolismo , Factores de Transcripción/genética , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Péptidos y Proteínas de Señalización Intracelular/genética , Proteínas Nucleares/metabolismo , Proteínas Nucleares/genética , Unión Proteica , Núcleo Celular/metabolismo , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , ADN/metabolismo , ADN/genéticaRESUMEN
Organ size is controlled by numerous factors including mechanical forces, which are mediated in part by the Hippo pathway. In growing Drosophila epithelial tissues, cytoskeletal tension influences Hippo signaling by modulating the localization of key pathway proteins to different apical domains. Here, we discovered a Hippo signaling hub at basal spot junctions, which form at the basal-most point of the lateral membranes and resemble adherens junctions in protein composition. Basal spot junctions recruit the central kinase Warts via Ajuba and E-cadherin, which prevent Warts activation by segregating it from upstream Hippo pathway proteins. Basal spot junctions are prominent when tissues undergo morphogenesis and are highly sensitive to fluctuations in cytoskeletal tension. They are distinct from focal adhesions, but the latter profoundly influences basal spot junction abundance by modulating the basal-medial actomyosin network and tension experienced by spot junctions. Thus, basal spot junctions couple morphogenetic forces to Hippo pathway activity and organ growth.
Asunto(s)
Proteínas de Drosophila , Verrugas , Animales , Drosophila/metabolismo , Vía de Señalización Hippo , Proteínas de Drosophila/metabolismo , Transducción de Señal , Uniones Adherentes/metabolismo , Verrugas/metabolismo , Morfogénesis/fisiologíaRESUMEN
Epithelial organs maintain their integrity and prevent tumor initiation by actively removing defective cells, such as those that have lost apicobasal polarity. Here, we identify how transcription factors of two key signaling pathways-Jun-N-terminal kinase (JNK) and Hippo-regulate epithelial integrity by controlling transcription of an overlapping set of target genes. Targeted DamID experiments reveal that, in proliferating cells of the Drosophila melanogaster eye, the AP-1 transcription factor Jun and the Hippo pathway transcription regulators Yorkie and Scalloped bind to a common suite of target genes that promote organ growth. In defective neoplastic cells, AP-1 transcription factors repress transcription of growth genes together with the C-terminal binding protein (CtBP) co-repressor. If gene repression by AP-1/CtBP fails, neoplastic tumor growth ensues, driven by Yorkie/Scalloped. Thus, AP-1/CtBP eliminates defective cells and prevents tumor initiation by acting in parallel to Yorkie/Scalloped to repress expression of a shared transcriptome. These findings shed new light on the maintenance of epithelial integrity and tumor suppression.
RESUMEN
Deregulation of the Hippo pathway is a driver for cancer progression and treatment resistance. In the context of gastric cancer, YAP1 is a biomarker for poor patient prognosis. Although genomic tumor profiling provides information of Hippo pathway activation, the present study demonstrates that inhibition of Yap1 activity has anti-tumor effects in gastric tumors driven by oncogenic mutations and inflammatory cytokines. We show that Yap1 is a key regulator of cell metabolism, proliferation, and immune responses in normal and neoplastic gastric epithelium. We propose that the Hippo pathway is targetable across gastric cancer subtypes and its therapeutic benefits are likely to be mediated by both cancer cell-intrinsic and -extrinsic mechanisms.
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Neoplasias Gástricas , Humanos , Neoplasias Gástricas/genética , Neoplasias Gástricas/metabolismo , Neoplasias Gástricas/patología , Microambiente Tumoral , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Vía de Señalización Hippo , Factor de Transcripción STAT3/metabolismoRESUMEN
The Salvador-Warts-Hippo (SWH) pathway contains multiple growth-inhibitory proteins that control organ size during development by limiting activity of the Yorkie oncoprotein. Increasing evidence indicates that these growth inhibitors act in a complex network upstream of Yorkie. This complexity is emphasised by the distinct phenotypes of tissue lacking different SWH pathway genes. For example, eye tissue lacking the core SWH pathway components salvador, warts or hippo is highly overgrown and resistant to developmental apoptosis, whereas tissue lacking fat or expanded is not. Here we explore the relative contribution of SWH pathway proteins to organ size control by determining their temporal activity profile throughout Drosophila melanogaster eye development. We show that eye tissue lacking fat, expanded or discs overgrown displays elevated Yorkie activity during the larval growth phase of development, but not in the pupal eye when apoptosis ensues. Fat and Expanded do possess Yorkie-repressive activity in the pupal eye, but loss of fat or expanded at this stage of development can be compensated for by Merlin. Fat appears to repress Yorkie independently of Dachs in the pupal eye, which would contrast with the mode of action of Fat during larval development. Fat is more likely to restrict Yorkie activity in the pupal eye together with Expanded, given that pupal eye tissue lacking both these genes resembles that of tissue lacking either gene. This study highlights the complexity employed by different SWH pathway proteins to control organ size at different stages of development.
Asunto(s)
Proteínas de Ciclo Celular/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/crecimiento & desarrollo , Péptidos y Proteínas de Señalización Intracelular/genética , Tamaño de los Órganos/genética , Proteínas Quinasas/genética , Proteínas Serina-Treonina Quinasas/genética , Animales , Animales Modificados Genéticamente , Moléculas de Adhesión Celular/genética , Moléculas de Adhesión Celular/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/fisiología , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/fisiología , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Ojo/crecimiento & desarrollo , Ojo/metabolismo , Regulación del Desarrollo de la Expresión Génica , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Péptidos y Proteínas de Señalización Intracelular/fisiología , Larva/genética , Larva/crecimiento & desarrollo , Larva/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Neurofibromina 2/genética , Neurofibromina 2/metabolismo , Proteínas Quinasas/metabolismo , Proteínas Quinasas/fisiología , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Serina-Treonina Quinasas/fisiología , Pupa/genética , Pupa/crecimiento & desarrollo , Pupa/metabolismo , Transducción de Señal/genética , Distribución TisularRESUMEN
The Hippo signaling pathway regulates developmental organ growth, regeneration, and cell fate decisions. Although the role of the Hippo pathway, and its transcriptional effectors YAP and TAZ, has been well documented in many cell types and species, only recently have the roles for this pathway come to light in vascular development and disease. Experiments in mice, zebrafish, and in vitro have uncovered roles for the Hippo pathway, YAP, and TAZ in vasculogenesis, angiogenesis, and lymphangiogenesis. In addition, the Hippo pathway has been implicated in vascular cancers and cardiovascular diseases, thus identifying it as a potential therapeutic target for the treatment of these conditions. However, despite recent advances, Hippo's role in the vasculature is still underappreciated compared with its role in epithelial tissues. In this review, we appraise our current understanding of the Hippo pathway in blood and lymphatic vessel development and highlight the current knowledge gaps and opportunities for further research.
Asunto(s)
Vía de Señalización Hippo , Transactivadores , Animales , Ratones , Transactivadores/metabolismo , Proteínas Señalizadoras YAP , Pez Cebra/metabolismo , LinfangiogénesisRESUMEN
The Germinal Center Kinase III (GckIII) pathway is a Hippo-like kinase module defined by sequential activation of Ste20 kinases Thousand and One (Tao) and GckIII, followed by nuclear dbf2-related (NDR) kinase Tricornered (Trc). We previously uncovered a role for the GckIII pathway in Drosophila melanogaster tracheal (respiratory) tube morphology. The trachea form a network of branched epithelial tubes essential for oxygen transport, and are structurally analogous to branched tubular organs in vertebrates, such as the vascular system. In the absence of GckIII pathway function, aberrant dilations form in tracheal tubes characterized by mislocalized junctional and apical proteins, suggesting that the pathway is important in maintaining tube integrity in development. Here, we observed a genetic interaction between trc and Cerebral cavernous malformations 3 (Ccm3), the Drosophila ortholog of a human vascular disease gene, supporting our hypothesis that the GckIII pathway functions downstream of Ccm3 in trachea, and potentially in the vertebrate cerebral vasculature. However, how GckIII pathway signaling is regulated and the mechanisms that underpin its function in tracheal development are unknown. We undertook biochemical and genetic approaches to identify proteins that interact with Trc, the most downstream GckIII pathway kinase. We found that known GckIII and NDR scaffold proteins are likely to control GckIII pathway signaling in tracheal development, consistent with their conserved roles in Hippo-like modules. Furthermore, we show genetic interactions between trc and multiple enzymes in glycolysis and oxidative phosphorylation, suggesting a potential function of the GckIII pathway in integrating cellular energy requirements with maintenance of tube integrity.
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Proteínas de Drosophila , Proteínas Serina-Treonina Quinasas , Animales , Humanos , Drosophila melanogaster/genética , Drosophila melanogaster/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Quinasas del Centro Germinal/genética , Quinasas del Centro Germinal/metabolismo , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de SeñalRESUMEN
During tissue regeneration, cell proliferation replaces missing structures to restore organ function. Regenerative potential differs greatly between organs and organisms; for example some amphibians can regrow entire limbs whereas mammals cannot. The process of regeneration relies on several signaling pathways that control developmental tissue growth, and implies the existence of organ size-control checkpoints that regulate both developmental, and regenerative, growth. Here we explore the role of one such checkpoint, the Salvador-Warts-Hippo pathway, in tissue regeneration. The Salvador-Warts-Hippo pathway limits tissue growth by repressing the Yorkie transcriptional co-activator. Several proteins serve as upstream modulators of this pathway including the atypical cadherins, Dachsous and Fat, whilst the atypical myosin, Dachs, functions downstream of Fat to activate Yorkie. Using Drosophila melanogaster imaginal discs we show that Salvador-Warts-Hippo pathway activity is repressed in regenerating tissue and that Yorkie is rate-limiting for regeneration of the developing wing. We show that regeneration is compromised in dachs mutant wing discs, but that proteins in addition to Fat and Dachs are likely to modulate Yorkie activity in regenerating cells. In conclusion our data reveal the importance of Yorkie hyperactivation for tissue regeneration and suggest that multiple upstream inputs, including Fat-Dachsous signaling, sense tissue damage and regulate Yorkie activity during regeneration of epithelial tissues.
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Proteínas de Ciclo Celular/fisiología , Proteínas de Drosophila/fisiología , Drosophila melanogaster/fisiología , Péptidos y Proteínas de Señalización Intracelular/fisiología , Proteínas Quinasas/fisiología , Proteínas Serina-Treonina Quinasas/fisiología , Regeneración , Transducción de Señal/fisiología , Animales , Apoptosis , Proteínas Nucleares/fisiología , Transactivadores/fisiología , Proteínas Señalizadoras YAPRESUMEN
The Hippo pathway is dysregulated in many different cancers, but point mutations in the pathway are rare. Transcriptional co-activator with PDZ-binding motif (TAZ) and Yes-associated protein (YAP) fusion proteins have emerged in almost all major cancer types and represent the most common genetic mechanism by which the two transcriptional co-activators are activated. Given that the N termini of TAZ or YAP are fused to the C terminus of another transcriptional regulator, the resultant fusion proteins hyperactivate a TEAD transcription factor-based transcriptome. Recent advances show that the C-terminal fusion partners confer oncogenic properties to TAZ/YAP fusion proteins by recruiting epigenetic modifiers that promote a hybrid TEAD-based transcriptome. Elucidating these cooperating epigenetic complexes represents a strategy to identify new therapeutic approaches for a pathway that has been recalcitrant to medical therapy.
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Neoplasias , Proteínas Señalizadoras YAP , Humanos , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Fosfoproteínas/genética , Fosfoproteínas/química , Fosfoproteínas/metabolismo , Péptidos y Proteínas de Señalización Intracelular , Transactivadores/genética , Transactivadores/metabolismo , Proteínas Serina-Treonina Quinasas , Transducción de Señal/genética , Proteínas Coactivadoras Transcripcionales con Motivo de Unión a PDZ , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Neoplasias/tratamiento farmacológico , Neoplasias/genéticaRESUMEN
The Apaf-1 protein is essential for cytochrome c-mediated caspase-9 activation in the intrinsic mammalian pathway of apoptosis. Although Apaf-1 is the only known mammalian homologue of the Caenorhabditis elegans CED-4 protein, the deficiency of apaf-1 in cells or in mice results in a limited cell survival phenotype, suggesting that alternative mechanisms of caspase activation and apoptosis exist in mammals. In Drosophila melanogaster, the only Apaf-1/CED-4 homologue, ARK, is required for the activation of the caspase-9/CED-3-like caspase DRONC. Using specific mutants that are deficient for ark function, we demonstrate that ARK is essential for most programmed cell death (PCD) during D. melanogaster development, as well as for radiation-induced apoptosis. ark mutant embryos have extra cells, and tissues such as brain lobes and wing discs are enlarged. These tissues from ark mutant larvae lack detectable PCD. During metamorphosis, larval salivary gland removal was severely delayed in ark mutants. However, PCD occurred normally in the larval midgut, suggesting that ARK-independent cell death pathways also exist in D. melanogaster.
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Apoptosis/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/embriología , Drosophila melanogaster/crecimiento & desarrollo , Regulación del Desarrollo de la Expresión Génica/genética , Animales , Apoptosis/efectos de la radiación , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Embrión no Mamífero/anomalías , Embrión no Mamífero/citología , Embrión no Mamífero/metabolismo , Evolución Molecular , Regulación del Desarrollo de la Expresión Génica/efectos de la radiación , Genes Letales/genética , Larva/genética , Larva/crecimiento & desarrollo , Larva/metabolismo , Metamorfosis Biológica/genética , Mutación/genética , Mutación/efectos de la radiación , Radiación Ionizante , Glándulas Salivales/citología , Glándulas Salivales/crecimiento & desarrollo , Glándulas Salivales/metabolismo , Transducción de Señal/genéticaRESUMEN
The Hippo pathway is a conserved signaling network that regulates organ growth and cell fate. One such cell fate decision is that of R8 photoreceptor cells in the Drosophila eye, where Hippo specifies whether cells sense blue or green light. We show that only a subset of proteins that control organ growth via the Hippo pathway also regulate R8 cell fate choice, including the STRIPAK complex, Tao, Pez, and 14-3-3 proteins. Furthermore, key Hippo pathway proteins were primarily cytoplasmic in R8 cells rather than localized to specific membrane domains, as in cells of growing epithelial organs. Additionally, Warts was the only Hippo pathway protein to be differentially expressed between R8 subtypes, while central Hippo pathway proteins were expressed at dramatically lower levels in adult and pupal eyes than in growing larval eyes. Therefore, we reveal several important differences in Hippo signaling in the contexts of organ growth and cell fate.
RESUMEN
Epithelioid hemangioendothelioma (EHE) is a vascular sarcoma that metastasizes early in its clinical course and lacks an effective medical therapy. The TAZ-CAMTA1 and YAP-TFE3 fusion proteins are chimeric transcription factors and initiating oncogenic drivers of EHE. A combined proteomic/genetic screen in human cell lines identified YEATS2 and ZZZ3, components of the Ada2a-containing histone acetyltransferase (ATAC) complex, as key interactors of both fusion proteins despite the dissimilarity of the C terminal fusion partners CAMTA1 and TFE3. Integrative next-generation sequencing approaches in human and murine cell lines showed that the fusion proteins drive a unique transcriptome by simultaneously hyperactivating a TEAD-based transcriptional program and modulating the chromatin environment via interaction with the ATAC complex. Interaction of the ATAC complex with both fusion proteins indicates that it is a key oncogenic driver and unifying enzymatic therapeutic target for this sarcoma. This study presents an approach to mechanistically dissect how chimeric transcription factors drive the formation of human cancers.
The proliferation of human cells is tightly regulated to ensure that enough cells are made to build and repair organs and tissues, while at the same time stopping cells from dividing uncontrollably and damaging the body. To get the right balance, cells rely on physical and chemical cues from their environment that trigger the biochemical signals that regulate two proteins called TAZ and YAP. These proteins control gene activity by regulating the rate at which genes are copied to produce proteins. If this process becomes dysregulated, cells can grow uncontrollably, causing cancer. In cancer cells, it is common to find TAZ and YAP fused to other proteins. In epithelioid hemangioendothelioma, a rare cancer that grows in the blood vessels, cancerous growth can be driven by a version of TAZ fused to the protein CAMTA1, or a version of YAP fused to the protein TFE3. While the role of TAZ and YAP in promoting gene activity is known, it is unclear how CAMTA1 and TFE3 contribute to cell growth becoming dysregulated. Merritt, Garcia et al. studied sarcoma cell lines to show that these two fusion proteins, TAZ-CAMTA1 and YAP-TFE3, change the pattern of gene activity seen in the cells compared to TAZ or YAP alone. An analysis of molecules that interact with the two fusion proteins identified a complex called ATAC as the cause of these changes. This complex adds chemical markers to DNA-packaging proteins, which control which genes are available for activation. The fusion proteins combine the ability of TAZ and YAP to control gene activity and the ability of CAMTA1 and TFE3 to make DNA more accessible, allowing the fusion proteins to drive uncontrolled cancerous growth. Similar TAZ and YAP fusion proteins have been found in other cancers, which can activate genes and potentially alter DNA packaging. Targeting drug development efforts at the proteins that complex with TAZ and YAP fusion proteins may lead to new therapies.