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BACKGROUND: Late vein graft failure is caused by intimal thickening resulting from endothelial cell (EC) damage and inflammation which promotes vascular smooth muscle cell (VSMC) dedifferentiation, migration, and proliferation. Nonphosphorylatable PRH (proline-rich homeodomain) S163C:S177C offers enhanced stability and sustained antimitotic effect. Therefore, we investigated whether adenovirus-delivered PRH S163C:S177C protein attenuates intimal thickening via VSMC phenotype modification without detrimental effects on ECs. METHODS: PRH S163C:S177C was expressed in vitro (human saphenous vein-VSMCs and human saphenous vein-ECs) and in vivo (ligated mouse carotid arteries) by adenoviruses. Proliferation, migration, and apoptosis were quantified and phenotype was assessed using Western blotting for contractile filament proteins and collagen gel contraction. EC inflammation was quantified using VCAM (vascular cell adhesion protein)-1, ICAM (intercellular adhesion molecule)-1, interleukin-6, and monocyte chemotactic factor-1 measurement and monocyte adhesion. Next Generation Sequencing was utilized to identify novel downstream mediators of PRH action and these and intimal thickening were investigated in vivo. RESULTS: PRH S163C:S177C inhibited proliferation, migration, and apoptosis and promoted contractile phenotype (enhanced contractile filament proteins and collagen gel contraction) compared with virus control in human saphenous vein-VSMCs. PRH S163C:S177C expression in human saphenous vein-ECs significantly reduced apoptosis, without affecting cell proliferation and migration, while reducing TNF (tumor necrosis factor)-α-induced VCAM-1 and ICAM-1 and monocyte adhesion and suppressing interleukin-6 and monocyte chemotactic factor-1 protein levels. PRH S163C:S177C expression in ligated murine carotid arteries significantly impaired carotid artery ligation-induced neointimal proliferation and thickening without reducing endothelial coverage. Next Generation Sequencing revealed STAT-1 (signal transducer and activator of transcription 1) and HDAC-9 (histone deacetylase 9) as mediators of PRH action and was supported by in vitro and in vivo analyses. CONCLUSIONS: We observed PRH S163C:S177C attenuated VSMC proliferation, and migration and enhanced VSMC differentiation at least in part via STAT-1 and HDAC-9 signaling while promoting endothelial repair and anti-inflammatory properties. These findings highlight the potential for PRH S163C:S177C to preserve endothelial function whilst suppressing intimal thickening, and reducing late vein graft failure.
Assuntos
Interleucina-6 , Túnica Íntima , Camundongos , Animais , Humanos , Interleucina-6/metabolismo , Túnica Íntima/patologia , Proliferação de Células , Neointima/patologia , Fatores Quimiotáticos/metabolismo , Fatores Quimiotáticos/farmacologia , Miócitos de Músculo Liso/metabolismo , Movimento CelularRESUMO
Urokinase-type plasminogen activator (uPA) regulates angiogenesis and vascular permeability through proteolytic degradation of extracellular matrix and intracellular signaling initiated upon its binding to uPAR/CD87 and other cell surface receptors. Here, we describe an additional mechanism by which uPA regulates angiogenesis. Ex vivo VEGF-induced vascular sprouting from Matrigel-embedded aortic rings isolated from uPA knock-out (uPA(-/-)) mice was impaired compared with vessels emanating from wild-type mice. Endothelial cells isolated from uPA(-/-) mice show less proliferation and migration in response to VEGF than their wild type counterparts or uPA(-/-) endothelial cells in which expression of wild type uPA had been restored. We reported previously that uPA is transported from cell surface receptors to nuclei through a mechanism that requires its kringle domain. Intranuclear uPA modulates gene transcription by binding to a subset of transcription factors. Here we report that wild type single-chain uPA, but not uPA variants incapable of nuclear transport, increases the expression of cell surface VEGF receptor 1 (VEGFR1) and VEGF receptor 2 (VEGFR2) by translocating to the nuclei of ECs. Intranuclear single-chain uPA binds directly to and interferes with the function of the transcription factor hematopoietically expressed homeodomain protein or proline-rich homeodomain protein (HHEX/PRH), which thereby lose their physiologic capacity to repress the activity of vehgr1 and vegfr2 gene promoters. These studies identify uPA-dependent de-repression of vegfr1 and vegfr2 gene transcription through binding to HHEX/PRH as a novel mechanism by which uPA mediates the pro-angiogenic effects of VEGF and identifies a potential new target for control of pathologic angiogenesis.
Assuntos
Proteínas de Homeodomínio/metabolismo , Neovascularização Fisiológica , Fatores de Transcrição/metabolismo , Ativador de Plasminogênio Tipo Uroquinase/metabolismo , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Animais , Movimento Celular/efeitos dos fármacos , Núcleo Celular/efeitos dos fármacos , Núcleo Celular/metabolismo , Proliferação de Células/efeitos dos fármacos , Células Endoteliais/citologia , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/metabolismo , Células HEK293 , Humanos , Células K562 , Camundongos Knockout , Neovascularização Fisiológica/efeitos dos fármacos , Regiões Promotoras Genéticas/genética , Ligação Proteica/efeitos dos fármacos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transdução de Sinais/efeitos dos fármacos , Fator A de Crescimento do Endotélio Vascular/farmacologia , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/genética , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/genéticaRESUMO
Protein kinase CK2 promotes cell survival and the activity of this kinase is elevated in several cancers including chronic myeloid leukaemia. We have shown previously that phosphorylation of the Proline-Rich Homeodomain protein (PRH/Hhex) by CK2 inhibits the DNA-binding activity of this transcription factor. Furthermore, PRH represses the transcription of multiple genes encoding components of the VEGF-signalling pathway and thereby influences cell survival. Here we show that the inhibitory effects of PRH on cell proliferation are abrogated by CK2 and that CK2 inhibits the binding of PRH at the Vegfr-1 promoter. Phosphorylation of PRH by CK2 also decreases the nuclear association of PRH and induces its cleavage by the proteasome. Moreover, cleavage of phosphorylated PRH produces a stable truncated cleavage product which we have termed PRHΔC (HhexΔC). PRHΔC acts as a transdominant negative regulator of full-length PRH by sequestering TLE proteins that function as PRH co-repressors. We show that this novel regulatory mechanism results in the alleviation of PRH-mediated repression of Vegfr-1. We suggest that the re-establishment of PRH function through inhibition of CK2 could be of value in treatment of myeloid leukaemias, as well as other tumour types in which PRH is inactivated by phosphorylation.
Assuntos
Caseína Quinase II/metabolismo , Proteínas de Homeodomínio/metabolismo , Fatores de Transcrição/metabolismo , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/genética , Proliferação de Células , Sobrevivência Celular , Proteínas de Homeodomínio/antagonistas & inibidores , Proteínas de Homeodomínio/genética , Humanos , Células K562 , Regiões Promotoras Genéticas , Estabilidade Proteica , Proteínas Repressoras/metabolismo , Deleção de Sequência , Transdução de Sinais/genética , Fatores de Transcrição/antagonistas & inibidores , Fatores de Transcrição/genética , Fator A de Crescimento do Endotélio Vascular/fisiologiaRESUMO
Quantum biological tunnelling for electron transfer is involved in controlling essential functions for life such as cellular respiration and homoeostasis. Understanding and controlling the quantum effects in biology has the potential to modulate biological functions. Here we merge wireless nano-electrochemical tools with cancer cells for control over electron transfer to trigger cancer cell death. Gold bipolar nanoelectrodes functionalized with redox-active cytochrome c and a redox mediator zinc porphyrin are developed as electric-field-stimulating bio-actuators, termed bio-nanoantennae. We show that a remote electrical input regulates electron transport between these redox molecules, which results in quantum biological tunnelling for electron transfer to trigger apoptosis in patient-derived cancer cells in a selective manner. Transcriptomics data show that the electric-field-induced bio-nanoantenna targets the cancer cells in a unique manner, representing electrically induced control of molecular signalling. The work shows the potential of quantum-based medical diagnostics and treatments.
Assuntos
Apoptose , Neoplasias , Humanos , Transporte de Elétrons , Oxirredução , Morte Celular , Ouro/químicaRESUMO
Protein self-organization is essential for the establishment and maintenance of nuclear architecture and for the regulation of gene expression. We have shown previously that the Proline-Rich Homeodomain protein (PRH/Hex) self-assembles to form oligomeric complexes that bind to arrays of PRH binding sites with high affinity and specificity. We have also shown that many PRH target genes contain suitably spaced arrays of PRH sites that allow this protein to bind and regulate transcription. Here, we use analytical ultracentrifugation and electron microscopy to further characterize PRH oligomers. We use the same techniques to show that PRH oligomers bound to long DNA fragments self-associate to form highly ordered assemblies. Electron microscopy and linear dichroism reveal that PRH oligomers can form protein-DNA fibres and that PRH is able to compact DNA in the absence of other proteins. Finally, we show that DNA compaction is not sufficient for the repression of PRH target genes in cells. We conclude that DNA compaction is a consequence of the binding of large PRH oligomers to arrays of binding sites and that PRH is functionally and structurally related to the Lrp/AsnC family of proteins from bacteria and archaea, a group of proteins formerly thought to be without eukaryotic equivalents.
Assuntos
DNA/química , Proteínas de Homeodomínio/química , Fatores de Transcrição/química , Sítios de Ligação , DNA/metabolismo , DNA/ultraestrutura , Proteínas de Homeodomínio/metabolismo , Proteínas de Homeodomínio/ultraestrutura , Humanos , Células K562 , Conformação de Ácido Nucleico , Multimerização Proteica , Fatores de Transcrição/metabolismo , Fatores de Transcrição/ultraestrutura , Transcrição GênicaRESUMO
Interactions between DNA and proteins are crucial for the regulation of gene expression. Chromatin immunoprecipitation (ChIP) is a powerful technique that allows the study of specific protein-DNA interactions in cultured cells and fresh or fixed tissue. Chromatin is isolated and sheared, and antibodies against the protein(s) of interest are used to isolate specific protein-DNA complexes. Subsequent analysis by real-time polymerase chain reaction (qPCR) or next-generation sequencing (NGS) allows identification and quantification of the co-purified DNA fragments, and NGS also gives insight into the genomic binding sites of a protein. Here we describe a cross-linking ChIP (X-ChIP) protocol, based around the example of a myc-tagged Proline-Rich Homeodomain (PRH) protein expressed in human umbilical vein endothelial cells. We also describe how to analyse specific known or suspected binding sites using quantitative PCR as well as how to analyse genome-wide binding from ChIP sequencing data.
Assuntos
Células Endoteliais , Fatores de Transcrição , Sítios de Ligação , Cromatina/genética , Imunoprecipitação da Cromatina/métodos , Células Endoteliais/metabolismo , Regulação da Expressão Gênica , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Authors would like to make a correction to the previous article [...].
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The proline-rich homeodomain protein (PRH/Hex) regulates transcription by binding to specific DNA sequences and regulates mRNA transport by binding to translation initiation factor eIF4E. Protein kinase CK2 plays multiple roles in the regulation of gene expression and cell proliferation. Here, we show that PRH interacts with the beta subunit of CK2 in vitro and in cells and that CK2 phosphorylates PRH. Phosphorylation of PRH by CK2 inhibits the DNA binding activity of this protein and dephosphorylation restores DNA binding indicating that this modification acts as a reversible switch. We show that phosphorylation of the homeodomain is sufficient to block DNA binding and we identify two amino acids within this the domain that are phosphorylated by CK2: S163 and S177. Site-directed mutagenesis demonstrates that mutation of either of these residues to glutamic acid partially mimics phosphorylation but is insufficient to completely block DNA binding whereas an S163E/S177E double mutation severely inhibits DNA binding. Significantly, the S163E and S177E mutations and the S163E/S177E double mutation all inhibit the ability of PRH to regulate transcription in cells. Since these amino acids are conserved between many homeodomain proteins, our results suggest that CK2 may regulate the activity of several homeodomain proteins in this manner.
Assuntos
Caseína Quinase II/metabolismo , Proteínas de Homeodomínio/metabolismo , Proteínas Repressoras/metabolismo , Fatores de Transcrição/metabolismo , Sequência de Aminoácidos , DNA/metabolismo , Proteínas de Homeodomínio/antagonistas & inibidores , Proteínas de Homeodomínio/química , Humanos , Células K562 , Dados de Sequência Molecular , Mutação , Fosfoproteínas/metabolismo , Fosforilação , Estrutura Terciária de Proteína , Proteínas Repressoras/antagonistas & inibidores , Proteínas Repressoras/química , Serina/metabolismo , Fatores de Transcrição/antagonistas & inibidores , Fatores de Transcrição/químicaRESUMO
Cholangiocarcinoma (CCA) is a disease with a very poor prognosis and limited treatment options. Although targeted therapies directed towards specific mutations found in CCA are becoming available and are showing great potential, many tumors do not carry actionable mutations and, in those that do, the emergence of drug resistance is a likely consequence of treatment. Therapeutic targeting of enzymes and other proteins that show elevated activity in CCA cells but which are not altered by mutation is a potential strategy for the treatment of target negative and drug-resistant disease. Protein kinase CK2 (CK2) is a ubiquitously expressed kinase that has increased expression and increased activity in a variety of cancer types including CCA. Several potent CK2 inhibitors are in pre-clinical development or under assessment in a variety of clinical trials often in combination with drugs that induce DNA damage. This review outlines the importance of CK2 in CCA and assesses the progress that has been made in the evaluation of CK2 inhibition as a treatment strategy in this disease. Targeting CK2 based on the expression levels or activity of this protein and/or in combination with drugs that induce DNA damage or inhibit cell cycle progression, could be a viable option for tumors that lack actionable mutations, or for tumors that develop resistance to targeted treatments.
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BACKGROUND: The incidence of cholangiocarcinoma (CCA) is increasing worldwide and current single chemotherapeutic drug treatments are ineffective. CX-4945 and cisplatin are currently in clinical trial for CCA treatment. MATERIALS AND METHODS: We assessed the effects of the sequence of administration of CX-4945 and cisplatin applied in combination treatments on their efficacy in CCA cells in vitro. CCA cell viability was examined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. Apoptosis was examined using flow cytometry. The percentage of cells positive for phosphorylated H2A histone family member X (γ-H2AX) were measured using both flow cytometry and immunofluorescence. RESULTS: CCA cell viability was reduced to 50% after 24 h of treatments with CX-4945 and cisplatin as single agents. Interestingly, treatment with cisplatin 6 h prior to CX-4945 treatment induced significantly more DNA damage and apoptosis than CX-4945 treatment followed by cisplatin. Unexpectedly, CX-4945 treatment followed by cisplatin was less effective than single treatment in RMCCA-1 CCA cells. In addition, a 1:1 ratio of each drug was the most effective combination in these cells. CONCLUSION: These data demonstrate that the combination of CX-4945 and cis platin acts additively when cisplatin is applied first, at least in part due to increased DNA damage and apoptosis. Furthermore, treatment with CX-4945 prior to cisplatin treatment reduces the efficacy of this drug combination in CCA cells.
Assuntos
Antineoplásicos/uso terapêutico , Colangiocarcinoma/tratamento farmacológico , Cisplatino/uso terapêutico , Naftiridinas/uso terapêutico , Fenazinas/uso terapêutico , Antineoplásicos/farmacologia , Proliferação de Células , Cisplatino/farmacologia , Combinação de Medicamentos , Sinergismo Farmacológico , Humanos , Naftiridinas/farmacologia , Fenazinas/farmacologiaRESUMO
The PRH (proline-rich homeodomain) [also known as Hex (haematopoietically expressed homeobox)] protein is a transcription factor that functions as an important regulator of vertebrate development and many other processes in the adult including haematopoiesis. The Groucho/TLE (transducin-like enhancer) family of co-repressor proteins also regulate development and modulate the activity of many DNA-binding transcription factors during a range of diverse cellular processes including haematopoiesis. We have shown previously that PRH is a repressor of transcription in haematopoietic cells and that an Eh-1 (Engrailed homology) motif present within the N-terminal transcription repression domain of PRH mediates binding to Groucho/TLE proteins and enables co-repression. In the present study we demonstrate that PRH regulates the nuclear retention of TLE proteins during cellular fractionation. We show that transcriptional repression and the nuclear retention of TLE proteins requires PRH to bind to both TLE and DNA. In addition, we characterize a trans-dominant-negative PRH protein that inhibits wild-type PRH activity by sequestering TLE proteins to specific subnuclear domains. These results demonstrate that transcriptional repression by PRH is dependent on TLE availability and suggest that subnuclear localization of TLE plays an important role in transcriptional repression by PRH.
Assuntos
Núcleo Celular/metabolismo , Proteínas de Homeodomínio/metabolismo , Proteínas Repressoras/metabolismo , Fatores de Transcrição/metabolismo , Western Blotting , Linhagem Celular Tumoral , Proteínas Correpressoras , DNA/metabolismo , Ensaio de Desvio de Mobilidade Eletroforética , Imunofluorescência , Proteínas de Homeodomínio/genética , Humanos , Imunoprecipitação , Mutação , Ligação Proteica , Fatores de Transcrição/genéticaRESUMO
Cancer cells go through a process known as epithelial-mesenchymal transition (EMT) during which they acquire the ability to migrate and invade extracellular matrix. Some cells also acquire the ability to move across a layer of endothelial cells to enter and exit the bloodstream; intra- and extravasation, respectively. The transcription factor PRH/HHEX (proline-rich homeodomain/haematopoietically expressed homeobox) controls cell proliferation and cell migration/invasion in a range of cell types. Our previous work showed that PRH activity is downregulated in prostate cancer cells owing to increased inhibitory PRH phosphorylation and that this increases cell proliferation and invasion. PRH inhibits migration and invasion by prostate and breast epithelial cells in part by activating the transcription of Endoglin, a transforming growth factor ß (TGFß) co-receptor. Here we show that depletion of PRH in immortalised prostate epithelial cells results in increased extravasation in vitro. We show that blood platelets stimulate extravasation of cells with depleted PRH and that inhibition of TGFß signalling blocks the effects of platelets on these cells. Moreover, TGFß induces changes characteristic of EMT including decreased E-Cadherin expression and increased Snail expression. We show that in prostate cells PRH regulates multiple genes involved in EMT and TGFß signalling. However, both platelets and TGFß increase PRH phosphorylation. In addition, TGFß increases binding of its effector pSMAD3 to the PRH/HHEX promoter and downregulates PRH protein and mRNA levels. Thus, TGFß signalling downregulates PRH activity by multiple mechanisms and induces an EMT that facilitates extravasation and sensitises cells to TGFß.
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Aberrant Notch and Wnt signaling are known drivers of cholangiocarcinoma (CCA), but the underlying factors that initiate and maintain these pathways are not known. Here, we show that the proline-rich homeodomain protein/hematopoietically expressed homeobox (PRH/HHEX) transcription factor forms a positive transcriptional feedback loop with Notch3 that is critical in CCA. PRH/HHEX expression is elevated in CCA, and depletion of PRH reduces CCA tumor growth in a xenograft model. Overexpression of PRH in primary human biliary epithelial cells is sufficient to increase cell proliferation and produce an invasive phenotype. Interrogation of the gene networks regulated by PRH and Notch3 reveals that unlike Notch3, PRH directly activates canonical Wnt signaling. These data indicate that hyperactivation of Notch and Wnt signaling is independent of the underlying mutational landscape and has a common origin in dysregulation of PRH. Moreover, they suggest new therapeutic options based on the dependence of specific Wnt, Notch, and CDK4/6 inhibitors on PRH activity. SIGNIFICANCE: The PRH/HHEX transcription factor is an oncogenic driver in cholangiocarcinoma that confers sensitivity to CDK4/6 inhibitors.
Assuntos
Antineoplásicos/farmacologia , Neoplasias dos Ductos Biliares/tratamento farmacológico , Colangiocarcinoma/tratamento farmacológico , Proteínas de Homeodomínio/metabolismo , Receptor Notch3/metabolismo , Fatores de Transcrição/metabolismo , Animais , Antineoplásicos/uso terapêutico , Neoplasias dos Ductos Biliares/genética , Neoplasias dos Ductos Biliares/patologia , Ductos Biliares Intra-Hepáticos/citologia , Ductos Biliares Intra-Hepáticos/patologia , Linhagem Celular Tumoral , Proliferação de Células/genética , Colangiocarcinoma/genética , Colangiocarcinoma/patologia , Quinase 4 Dependente de Ciclina/antagonistas & inibidores , Quinase 6 Dependente de Ciclina/antagonistas & inibidores , Resistencia a Medicamentos Antineoplásicos/genética , Células Epiteliais , Regulação Neoplásica da Expressão Gênica , Técnicas de Silenciamento de Genes , Redes Reguladoras de Genes , Proteínas de Homeodomínio/genética , Humanos , Células K562 , Masculino , Camundongos , Mutação , Invasividade Neoplásica/genética , Piperazinas/farmacologia , Piperazinas/uso terapêutico , Cultura Primária de Células , Regiões Promotoras Genéticas , Piridinas/farmacologia , Piridinas/uso terapêutico , RNA-Seq , Fatores de Transcrição/genética , Via de Sinalização Wnt/genética , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
The PRH (proline-rich homeodomain) [also known as Hex (haematopoietically expressed homeobox)] protein is a critical regulator of vertebrate development. PRH is able to regulate cell proliferation and differentiation and is required for the formation of the vertebrate body axis, the haematopoietic and vascular systems and the formation of many vital organs. PRH is a DNA-binding protein that can repress and activate the transcription of its target genes using multiple mechanisms. In addition, PRH can regulate the nuclear transport of specific mRNAs making PRH a member of a select group of proteins that control gene expression at the transcriptional and translational levels. Recent biophysical analysis of the PRH protein has shown that it forms homo-oligomeric complexes in vivo and in vitro and that the proline-rich region of PRH forms a novel dimerization interface. Here we will review the current literature on PRH and discuss the complex web of interactions centred on this multifunctional protein.
Assuntos
Proteínas de Homeodomínio/genética , Fatores de Transcrição/genética , Sequência de Aminoácidos , Animais , Proteínas Aviárias/genética , Proteínas Aviárias/metabolismo , Proliferação de Células , Dimerização , Proteínas de Homeodomínio/metabolismo , Humanos , Modelos Biológicos , Dados de Sequência Molecular , Estrutura Terciária de Proteína , Alinhamento de Sequência , Fatores de Transcrição/metabolismo , Transcrição GênicaRESUMO
Cholangiocarcinoma is a disease with a poor prognosis and increasing incidence and hence there is a pressing unmet clinical need for new adjuvant treatments. Protein kinase CK2 (previously casein kinase II) is a ubiquitously expressed protein kinase that is up-regulated in multiple cancer cell types. The inhibition of CK2 activity using CX-4945 (Silmitasertib) has been proposed as a novel treatment in multiple disease settings including cholangiocarcinoma. Here, we show that CX-4945 inhibited the proliferation of cholangiocarcinoma cell lines in vitro. Moreover, CX-4945 treatment induced the formation of cytosolic vacuoles in cholangiocarcinoma cell lines and other cancer cell lines. The vacuoles contained extracellular fluid and had neutral pH, features characteristic of methuosis. In contrast, simultaneous knockdown of both the α and α' catalytic subunits of protein kinase CK2 using small interfering RNA (siRNA) had little or no effect on the proliferation of cholangiocarcinoma cell lines and failed to induce the vacuole formation. Surprisingly, low doses of CX-4945 increased the invasive properties of cholangiocarcinoma cells due to an upregulation of matrix metallopeptidase 7 (MMP-7), while the knockdown of CK2 inhibited cell invasion. Our data suggest that CX-4945 inhibits cell proliferation and induces cell death via CK2-independent pathways. Moreover, the increase in cell invasion brought about by CX-4945 treatment suggests that this drug might increase tumor invasion in clinical settings.
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Formation of the lymphatic system requires the coordinated expression of several key regulators: vascular endothelial growth factor C (VEGFC), its receptor FLT4, and a key transcriptional effector, PROX1. Yet, how expression of these signaling components is regulated remains poorly understood. Here, using a combination of genetic and molecular approaches, we identify the transcription factor hematopoietically expressed homeobox (HHEX) as an upstream regulator of VEGFC, FLT4, and PROX1 during angiogenic sprouting and lymphatic formation in vertebrates. By analyzing zebrafish mutants, we found that hhex is necessary for sprouting angiogenesis from the posterior cardinal vein, a process required for lymphangiogenesis. Furthermore, studies of mammalian HHEX using tissue-specific genetic deletions in mouse and knockdowns in cultured human endothelial cells reveal its highly conserved function during vascular and lymphatic development. Our findings that HHEX is essential for the regulation of the VEGFC/FLT4/PROX1 axis provide insights into the molecular regulation of lymphangiogenesis.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Homeodomínio/genética , Linfangiogênese/genética , Proteínas Repressoras/genética , Proteínas Supressoras de Tumor/genética , Fator C de Crescimento do Endotélio Vascular/genética , Receptor 3 de Fatores de Crescimento do Endotélio Vascular/genética , Proteínas de Peixe-Zebra/genética , Animais , Animais Geneticamente Modificados , Sequência de Bases , Vasos Sanguíneos/citologia , Vasos Sanguíneos/crescimento & desenvolvimento , Vasos Sanguíneos/metabolismo , Linhagem Celular , Embrião de Mamíferos , Embrião não Mamífero , Células Endoteliais/citologia , Células Endoteliais/metabolismo , Proteínas de Homeodomínio/metabolismo , Humanos , Vasos Linfáticos/citologia , Vasos Linfáticos/metabolismo , Camundongos , Neovascularização Fisiológica/genética , Proteínas Repressoras/deficiência , Transdução de Sinais , Transcrição Gênica , Proteínas Supressoras de Tumor/metabolismo , Fator C de Crescimento do Endotélio Vascular/metabolismo , Receptor 3 de Fatores de Crescimento do Endotélio Vascular/metabolismo , Peixe-Zebra , Proteínas de Peixe-Zebra/deficiência , Proteínas de Peixe-Zebra/metabolismoRESUMO
Homeodomain proteins regulate multiple developmental pathways by altering gene expression temporally and in a tissue-specific fashion. The Proline Rich Homeodomain protein (PRH/Hex) is a transcription factor and an essential regulator of embryonic development and haematopoiesis. Recent discoveries have implicated self-association as an important feature of transcription factor function. Here, we show using a variety of techniques including gel-filtration, analytical ultracentrifugation, electron microscopy and in vitro cross-linking, that purified recombinant PRH is oligomeric and we use in vivo cross-linking to confirm that this protein exists as oligomers in cells. This is the first demonstration that a homeodomain protein can oligomerise in vivo. Consistent with these findings we show that a fraction of endogenous and exogenous PRH appears as discrete foci within the nucleus and at the nuclear periphery. The N-terminal domain of PRH is involved in the regulation of cell proliferation and transcriptional repression and can make multiple protein-protein interactions. We show that this region of PRH contains a novel proline-rich dimerisation domain that mediates oligomerisation. We propose a model that explains how PRH forms oligomers and we discuss how these oligomers might control transcription.
Assuntos
Proteínas de Homeodomínio/química , Fatores de Transcrição/química , Sequência de Aminoácidos , Animais , Sequência de Bases , Células COS , Linhagem Celular , Núcleo Celular/metabolismo , Fenômenos Químicos , Físico-Química , Chlorocebus aethiops , DNA/genética , DNA/metabolismo , Dimerização , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Humanos , Técnicas In Vitro , Células K562 , Microscopia Eletrônica , Modelos Moleculares , Dados de Sequência Molecular , Prolina/química , Estrutura Quaternária de Proteína , Estrutura Terciária de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Soluções , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição GênicaRESUMO
The Proline-Rich Homeodomain (PRH) protein is a regulator of transcription and translation and plays a key role in the control of cell proliferation and cell differentiation. PRH contains an N-terminal proline-rich domain that can repress transcription when expressed as a fusion protein with an unrelated DNA binding domain, a central homeodomain that binds to specific DNA sequences and an acidic C-terminal domain of no known function. In order to investigate the structure and functions of PRH we have purified the full-length protein and truncated proteins corresponding to different domains of PRH fused to histidine tags. Here we compare the effects of elution conditions and column volume on protein purification and we investigate the DNA binding activity of these proteins. We show that the PRH homeodomain co-purifies with nucleic acids even after nuclease treatment and that a high salt-wash is required to remove bound nucleic acids. In contrast with the full-length PRH protein, the PRH homeodomain binds to DNA with high affinity. We show that a truncated protein comprising the homeodomain and C-terminal domain also binds to DNA with high affinity and we conclude that the N-terminal domain of PRH inhibits the homeodomain-DNA interaction.
Assuntos
DNA/química , Proteínas de Homeodomínio/química , Proteínas de Homeodomínio/isolamento & purificação , Fatores de Transcrição/química , Fatores de Transcrição/isolamento & purificação , Sequência de Aminoácidos/genética , DNA/metabolismo , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Humanos , Ligação Proteica/genética , Estrutura Terciária de Proteína/genética , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/isolamento & purificação , Proteínas Recombinantes de Fusão/metabolismo , Deleção de Sequência/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
The proline rich homeodomain protein (PRH), also known as haematopoietically expressed homeobox (HHEX), is an essential transcription factor in embryonic development and in the adult. The PRH protein forms oligomeric complexes that bind to tandemly repeated PRH recognition sequences within or at a distance from PRH-target genes and recruit a variety of PRH-interacting proteins. PRH can also bind to other transcription factors and co-regulate specific target genes either directly through DNA binding, or indirectly through effects on the activity of its partner proteins. In addition, like some other homeodomain proteins, PRH can regulate the translation of specific mRNAs. Altered PRH expression and altered PRH intracellular localisation, are associated with breast cancer, liver cancer and thyroid cancer and some subtypes of leukaemia. This is consistent with the involvement of multiple PRH-interacting proteins, including the oncoprotein c-Myc, translation initiation factor 4E (eIF4E), and the promyelocytic leukaemia protein (PML), in the control of cell proliferation and cell survival. Similarly, multiple PRH target genes, including the genes encoding vascular endothelial growth factor (VEGF), VEGF receptors, Endoglin, and Goosecoid, are known to be important in the control of cell proliferation and cell survival and/or the regulation of cell migration and invasion. In this review, we summarise the evidence that implicates PRH in tumourigenesis and we review the data that suggests PRH levels could be useful in cancer prognosis and in the choice of treatment options.
RESUMO
PRH (proline-rich homeodomain protein)/Hex is important in the control of cell proliferation and differentiation. We have shown previously that PRH contains two domains that can bring about transcriptional repression independently; the PRH homeodomain represses transcription by binding to TATA box sequences, whereas the proline-rich N-terminal domain can repress transcription by interacting with members of the Groucho/TLE (transducin-like enhancer of split) family of co-repressor proteins. The proteasome is a multi-subunit protein complex involved in the processing and degradation of proteins. Some proteasome subunits have been suggested to play a role in the regulation of transcription. In the present study, we show that PRH interacts with the HC8 subunit of the proteasome in the context of both 20 and 26 S proteasomes. Moreover, we show that PRH is associated with the proteasome in haematopoietic cells and that the proline-rich PRH N-terminal domain is responsible for this interaction. Whereas PRH can be cleaved by the proteasome, it does not appear to be degraded rapidly in vitro or in vivo, and the proteolytic activity of the proteasome is not required for transcriptional repression by PRH. However, proteasomal digestion of PRH can liberate truncated PRH proteins that retain the ability to bind to DNA. We discuss these findings in terms of the biological role of PRH in gene regulation and the control of cell proliferation.