RESUMO
Centromeres are specialized chromosome loci that seed the kinetochore, a large protein complex that effects chromosome segregation. A 16-subunit complex, the constitutive centromere associated network (CCAN), connects between the specialized centromeric chromatin, marked by the histone H3 variant CENP-A, and the spindle-binding moiety of the kinetochore. Here, we report a cryo-electron microscopy structure of human CCAN. We highlight unique features such as the pseudo GTPase CENP-M and report how a crucial CENP-C motif binds the CENP-LN complex. The CCAN structure has implications for the mechanism of specific recognition of the CENP-A nucleosome. A model consistent with our structure depicts the CENP-C-bound nucleosome as connected to the CCAN through extended, flexible regions of CENP-C. An alternative model identifies both CENP-C and CENP-N as specificity determinants but requires CENP-N to bind CENP-A in a mode distinct from the classical nucleosome octamer.
Assuntos
Cinetocoros , Nucleossomos , Centrômero/metabolismo , Proteína Centromérica A/metabolismo , Microscopia Crioeletrônica , Humanos , Cinetocoros/metabolismo , Nucleossomos/genéticaRESUMO
The Epstein-Barr virus (EBV) transforms resting B cells and is involved in the development of B cell lymphomas. We report here that the viral noncoding RNA EBER2 accelerates B cell growth by potentiating expression of the UCHL1 deubiquitinase that itself increased expression of the Aurora kinases and of cyclin B1. Importantly, this effect was also visible in Burkitt's lymphoma cells that express none of the virus's known oncogenes. Mechanistically, EBER2 bound the UCHL1 messenger RNA (mRNA), thereby bringing a protein complex that includes PU.1, a UCHL1 transactivator, to the vicinity of its promoter. Although the EBV oncogene LMP1 has been suggested to induce UCHL1, we show here that EBER2 plays a much more important role to reach significant levels of the deubiquitinase in infected cells. However, some viruses that carried a polymorphic LMP1 had an increased ability to achieve full UCHL1 expression. This work identifies a direct cellular target of a viral noncoding RNA that is likely to be central to EBV's oncogenic properties.
Assuntos
Proliferação de Células/fisiologia , Enzimas Desubiquitinantes/genética , Herpesvirus Humano 4/fisiologia , RNA Viral/fisiologia , Ativação Transcricional/fisiologia , Linfócitos B/citologia , HumanosRESUMO
During prolonged mitotic arrest induced by antimicrotubule drugs, cell fate decision is determined by two alternative pathways, one leading to cell death and the other inducing premature escape from mitosis by mitotic slippage. FBWX7, a member of the F-box family of proteins and substrate-targeting subunit of the SKP1-CUL1-F-Box E3 ubiquitin ligase complex, promotes mitotic cell death and prevents mitotic slippage, but molecular details underlying these roles for FBWX7 are unclear. In this study, we report that WDR5 (WD-repeat containing protein 5), a component of the mixed lineage leukemia complex of histone 3 lysine 4 methyltransferases, is a substrate of FBXW7. We determined by coimmunoprecipitation experiments and in vitro binding assays that WDR5 interacts with FBXW7 in vivo and in vitro. SKP1-CUL1-F-Box-FBXW7 mediates ubiquitination of WDR5 and targets it for proteasomal degradation. Furthermore, we find that WDR5 depletion counteracts FBXW7 loss of function by reducing mitotic slippage and polyploidization. In conclusion, our data elucidate a new mechanism in mitotic cell fate regulation, which might contribute to prevent chemotherapy resistance in patients after antimicrotubule drug treatment.
Assuntos
Proteína 7 com Repetições F-Box-WD , Histona-Lisina N-Metiltransferase , Peptídeos e Proteínas de Sinalização Intracelular , Humanos , Proteínas de Ciclo Celular/metabolismo , Proteína 7 com Repetições F-Box-WD/metabolismo , Histona-Lisina N-Metiltransferase/metabolismo , Histonas/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Lisina/metabolismo , Proteínas Ligases SKP Culina F-Box/genética , Proteínas Ligases SKP Culina F-Box/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , UbiquitinaçãoRESUMO
INTRODUCTION: Recombinant coagulation factor VIII (FVIII) products are the standard of care for patients with haemophilia A. The development of modified FVIII products has provided benefit for patients but presented challenges for monitoring FVIII activity. AIM: This single-centre study evaluated the Roche FVIII one-stage clotting assay (OSA) in measuring FVIII activity in plasma samples spiked with seven FVIII products at clinically relevant concentrations. METHODS: FVIII-deficient plasma samples were spiked with two batches of recombinant FVIII products (octocog alfa, moroctocog alfa, simoctocog alfa, efmoroctocog alfa, damoctocog alfa pegol, rurioctocog alfa pegol, lonoctocog alfa) at 1-120 IU/dL FVIII activity, according to their labelled potency. Measurement was conducted on the cobas t 511/711 analysers using the Roche FVIII OSA and the Technoclone TECHNOCHROM FVIII:C chromogenic substrate assay (CSA). RESULTS: Using the OSA, FVIII activity was close to labelled potency for most analysed FVIII products including a recombinant FVIII Fc fusion protein. PEGylated FVIII product, damoctocog alfa pegol, was marginally above and single-chain product, lonoctocog alfa, below the predefined acceptance criteria: for FVIII activity < 25 IU/dL: ± 5 IU/dL; for FVIII activity ≥ 25 IU/dL: ± 20% (relative). The different principles of OSA and CSA led to discrepancies in the estimation of all analysed FVIII products. Additionally, in vitro recovery was increased at lower levels of FVIII activity using the OSA, whereas recovery was more consistent using the CSA. CONCLUSION: These data allow the interpretation of FVIII activity results for different FVIII products using the Roche FVIII OSA on the cobas t 511/711 analysers.
Assuntos
Hemofilia A , Hemostáticos , Testes de Coagulação Sanguínea , Fator VIII , Hemofilia A/tratamento farmacológico , HumanosRESUMO
Correct spindle orientation is achieved through signaling pathways that provide a molecular link between the cell cortex and spindle microtubules in an F-actin-dependent manner. A conserved cortical protein complex, composed of LGN (also known as GPSM2), NuMA (also known as NUMA1) and dynein-dynactin, plays a key role in establishing proper spindle orientation. It has also been shown that the actin-binding protein MISP and the ERM family, which are activated by lymphocyte-oriented kinase (LOK, also known as STK10) and Ste20-like kinase (SLK) (hereafter, SLK/LOK) in mitosis, regulate spindle orientation. Here, we report that MISP functions downstream of the ERM family member ezrin and upstream of NuMA to allow optimal spindle positioning. We show that MISP directly interacts with ezrin and that SLK/LOK-activated ezrin ensures appropriate cortical MISP levels in mitosis by competing with MISP for actin-binding sites at the cell cortex. Furthermore, we found that regulation of the correct cortical MISP levels, by preventing its excessive accumulation, is essential for crescent-like polarized NuMA localization at the cortex and, as a consequence, leads to highly dynamic astral microtubules. Our results uncover how appropriate MISP levels at the cortex are required for proper NuMA polarization and, therefore, an optimal placement of the mitotic spindle within the cell.This article has an associated First Person interview with the first author of the paper.
Assuntos
Antígenos Nucleares/metabolismo , Proteínas de Ciclo Celular/metabolismo , Proteínas do Citoesqueleto/metabolismo , Proteínas dos Microfilamentos/metabolismo , Proteínas Associadas à Matriz Nuclear/metabolismo , Fosfoproteínas/metabolismo , Fuso Acromático/metabolismo , Actinas/genética , Actinas/metabolismo , Antígenos Nucleares/genética , Proteínas de Ciclo Celular/genética , Proteínas do Citoesqueleto/genética , Complexo Dinactina/genética , Complexo Dinactina/metabolismo , Dineínas/genética , Dineínas/metabolismo , Células HeLa , Humanos , Proteínas dos Microfilamentos/genética , Proteínas Associadas à Matriz Nuclear/genética , Fosfoproteínas/genética , Ligação Proteica , Fuso Acromático/química , Fuso Acromático/genéticaRESUMO
Glyphosate (N-[phosphonomethyl]-glycine) is the most widely used herbicide worldwide. Due to health concerns about glyphosate exposure, its continued use is controversially discussed. Biomonitoring is an important tool in safety evaluation and this study aimed to determine exposure to glyphosate and its metabolite AMPA, in association with food consumption data, in participants of the cross-sectional KarMeN study (Germany). Glyphosate and AMPA levels were measured in 24-h urine samples from study participants (n = 301). For safety evaluation, the intake of glyphosate and AMPA was calculated based on urinary concentrations and checked against the EU acceptable daily intake (ADI) value for glyphosate. Urinary excretion of glyphosate and/or AMPA was correlated with food consumption data. 8.3% of the participants (n = 25) exhibited quantifiable concentrations (> 0.2 µg/L) of glyphosate and/or AMPA in their urine. In 66.5% of the samples, neither glyphosate (< 0.05 µg/L) nor AMPA (< 0.09 µg/L) was detected. The remaining subjects (n = 76) showed traces of glyphosate and/or AMPA. The calculated glyphosate and/or AMPA intake was far below the ADI of glyphosate. Significant, positive associations between urinary glyphosate excretion and consumption of pulses, or urinary AMPA excretion and mushroom intake were observed. Despite the widespread use of glyphosate, the exposure of the KarMeN population to glyphosate and AMPA was found to be very low. Based on the current risk assessment of glyphosate by EFSA, such exposure levels are not expected to pose any risk to human health. The detected associations with consuming certain foods are in line with reports on glyphosate and AMPA residues in food.
Assuntos
Exposição Dietética/estatística & dados numéricos , Glicina/análogos & derivados , Herbicidas/urina , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico/urina , Estudos Transversais , Dieta/estatística & dados numéricos , Monitoramento Ambiental , Alemanha , Glicina/urina , GlifosatoRESUMO
PURPOSE: Comparison of food consumption, nutrient intake and underreporting of diet history interviews, 24-h recalls and weighed food records to gain further insight into specific strength and limitations of each method and to support the choice of the adequate dietary assessment method. METHODS: For 677 participants (14-80 years) of the German National Nutrition Survey II confidence intervals for food consumption and nutrient intake were calculated on basis of bootstrapping samples, Cohen's d for the relevance of differences, and intraclass correlation coefficients for the degree of agreement of dietary assessment methods. Low energy reporters were identified with Goldberg cut-offs. RESULTS: In 7 of 18 food groups diet history interviews showed higher consumption means than 24-h recalls and weighed food records. Especially mean values of food groups perceived as socially desirable, such as fruit and vegetables, were highest for diet history interviews. For "raw" and "cooked vegetables", the diet history interviews showed a mean consumption of 144 and 109 g/day in comparison with 68 and 70 g/day in 24-h recalls and 76 and 75 g/day in weighed food records, respectively. For "fruit", diet history interviews showed a mean consumption of 256 g/day in comparison with 164 g/day in 24-h recalls and 147 g/day in weighed food records. No major differences regarding underreporting of energy intake were found between dietary assessment methods. CONCLUSIONS: With regard to estimating food consumption and nutrient intake, 24-h recalls and weighed food records showed smaller differences and better agreement than pairwise comparisons with diet history interviews.
Assuntos
Registros de Dieta , Dieta/métodos , Ingestão de Energia , Avaliação Nutricional , Inquéritos Nutricionais/métodos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Dieta/estatística & dados numéricos , Comportamento Alimentar , Feminino , Alemanha , Humanos , Masculino , Pessoa de Meia-Idade , Inquéritos Nutricionais/estatística & dados numéricos , Estado Nutricional , Adulto JovemRESUMO
Centrioles are core components of centrosomes, the major microtubule-organizing centers of animal cells, and act as basal bodies for cilia formation. Control of centriole number is therefore crucial for genome stability and embryogenesis. Centriole duplication requires the serine/threonine protein kinase Plk4. Here, we identify Cep78 as a human centrosomal protein and a new interaction partner of Plk4. Cep78 is mainly a centriolar protein that localizes to the centriolar wall. Furthermore, we find that Plk4 binds to Cep78 through its N-terminal domain but that Cep78 is not an in vitro Plk4 substrate. Cep78 colocalizes with Plk4 at centrioles and is required for Plk4-induced centriole overduplication. Interestingly, upon depletion of Cep78, newly synthesized Plk4 is not localized to centrosomes. Our results suggest that the interaction between Cep78 and the N-terminal catalytic domain of Plk4 is a new and important element in the centrosome overduplication process.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Centríolos/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Células HeLa , Humanos , Interfase , Ligação Proteica , Transporte ProteicoRESUMO
OBJECTIVE: To characterise German vitamin and mineral supplement users differentiated by their motives for supplement use. DESIGN: Data were obtained from the German National Nutrition Monitoring (2010/11) via two 24 h dietary recalls and a telephone interview. Motive-based subgroups of supplement users were identified by factor and cluster analysis. Sociodemographic, lifestyle, health and dietary characteristics and supplement use were examined. Differences were analysed using χ 2 tests, logistic and linear regression models. SETTING: Germany, nationwide. SUBJECTS: Individuals (n 1589) aged 18-80 years. RESULTS: Three motive-based subgroups were identified: a 'Prevention' subgroup (n 324), characterised by the motive to prevent nutrient deficiencies; a 'Prevention and additional benefits' subgroup (n 166), characterised by motives to prevent health problems and improve well-being and performance; and a 'Treatment' subgroup (n 136), characterised by motives to treat nutrient deficiencies or diseases. Members of the two prevention subgroups had a higher Healthy Eating Index score and tended to be more physically active than non-users. Those in the 'Prevention and additional benefits' subgroup supplemented with a greater number of micronutrients. Members of the 'Treatment' subgroup tended to be older and have a lower self-reported health status than non-users, and supplemented with a smaller number of micronutrients. CONCLUSIONS: The majority of supplement users take supplements for preventive purposes and they are more health conscious than non-users of supplements due to their concerns about developing health problems. Those supplementing for treatment purposes may have underlying health indications and may be more likely to benefit from supplementation than those supplementing for preventive purposes.
Assuntos
Inquéritos sobre Dietas , Suplementos Nutricionais , Micronutrientes/administração & dosagem , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Índice de Massa Corporal , Estudos Transversais , Dieta , Feminino , Alemanha , Nível de Saúde , Humanos , Estilo de Vida , Masculino , Micronutrientes/sangue , Micronutrientes/deficiência , Pessoa de Meia-Idade , Motivação , Adulto JovemRESUMO
The German National Nutrition Monitoring (NEMONIT) is a longitudinal and nationwide study to assess changes in food consumption and nutrient intake in Germany. A sample of 1840 participants (baseline age: 14-80 years) was drawn from the nationally representative German National Nutrition Survey (NVS) II (2005-2007). The participants have been interviewed by telephone annually since 2008. Food consumption was assessed by two 24-h recalls in the NVS II and the 4 years of NEMONIT (2008-2012/2013), respectively. Energy and nutrient intakes were calculated using the German Nutrient Database 3.02. Diet quality was evaluated using the Healthy Eating Index-NVS (HEI-NVS) II. Time trends were analysed by generalised estimating equation. Consumption of fruit/fruit products and fruit juice/nectar among men and women decreased, whereas consumption of water, soft drinks and coffee/tea increased over the 6-year period. Furthermore, increased consumption of confectionery and animal fats was observed among women. HEI-NVS II did not change since NVS II in both sexes. There were no changes in energy and protein intakes, but carbohydrate intake declined while fat intake increased over time. Regarding micronutrients, a decreasing intake of thiamin, riboflavin and vitamin B6 was observed in both sexes, but intake of Mg, Fe and niacin increased among women over time. In conclusion, food consumption and nutrient intake remained relatively stable between 2005-2007 and 2012/2013 within this German cohort. A few favourable and unfavourable changes were observed. Compared with national dietary guidelines, consumption of food of plant origin remained too low and consumption of meat/meat products remained too high in Germany.
Assuntos
Dieta/tendências , Inquéritos Nutricionais , Adolescente , Adulto , Idoso , Animais , Doces , Bebidas Gaseificadas , Café , Dieta Saudável/estatística & dados numéricos , Gorduras na Dieta/administração & dosagem , Ingestão de Energia , Comportamento Alimentar , Feminino , Alimentos , Preferências Alimentares , Frutas , Alemanha , Humanos , Estudos Longitudinais , Masculino , Carne , Micronutrientes/administração & dosagem , Pessoa de Meia-Idade , Política Nutricional , Valor Nutritivo , Fatores Sexuais , Chá , Adulto JovemRESUMO
The aim of this article is to demonstrate the complexity of nutritional behavior and to increase understanding of this complex phenomenon. We developed a cause-effect model based on current literature, expert consultation, and instruments dealing with complexity. It presents factors from all dimensions of nutrition and their direct causal relationships with specification of direction, strength, and type. Including the interplay of all relationships, the model reveals cause-effect chains, feedback loops, multicausalities, and side effects. Analyses based on the model can further enhance understanding of nutritional behavior and help identify starting points for measures to modify food consumption.
Assuntos
Envelhecimento , Regulação do Apetite , Dieta Saudável , Conhecimentos, Atitudes e Prática em Saúde , Estilo de Vida Saudável , Modelos Psicológicos , Socialização , Adolescente , Adulto , Idoso , Envelhecimento/etnologia , Regulação do Apetite/etnologia , Causalidade , Criança , Dieta Saudável/etnologia , Dieta Saudável/psicologia , Escolaridade , Exercício Físico , Família/etnologia , Feminino , Abastecimento de Alimentos , Alemanha , Conhecimentos, Atitudes e Prática em Saúde/etnologia , Humanos , Masculino , Meios de Comunicação de Massa , Influência dos Pares , Pesquisa QualitativaRESUMO
The second German National Nutrition Survey (NVS II) aimed to evaluate food consumption and other aspects of nutritional behaviour of a representative sample of the German population, using a modular design with three different dietary assessment methods. To assess usual food consumption, 15,371 German speaking subjects 14-80 years of age completed a diet history interview between November 2005 and November 2006. With reference to the guidelines of the German Nutrition Society (DGE), NVS II observed that the German population did not eat enough foods of plant origin, especially vegetables and consumed too much of meat and meat products. While generally similar food consumption is observed in other European countries, consumption of bread, fruit juices/nectars and beer is higher in Germany. On average, men consumed two times more meat and soft drinks as well as six times more beer than women did, whereas the consumption of vegetables, fruit as well as herbal/fruit tea was higher in women. Older participants showed a lower consumption of meat, fruit juice/nectars, soft drinks and spirits as well as a higher consumption of fish, vegetables, fruit, and herbal/fruit tea than adolescents and younger adults did. There are also differences in food consumption with regard to socio-economic status (SES). Persons with higher SES consumed more vegetables, fruit, fish, water, coffee/tea and wine, while persons with lower SES consumed more meat and meat products, soft drinks and beer. In general, the food consumption of women, the elderly and the higher SES group tends to be closer to the official dietary guidelines in Germany.
Assuntos
Dieta/efeitos adversos , Promoção da Saúde , Política Nutricional , Cooperação do Paciente , Adolescente , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Dieta/etnologia , Feminino , Alemanha , Humanos , Masculino , Pessoa de Meia-Idade , Inquéritos Nutricionais , Valor Nutritivo , Cooperação do Paciente/etnologia , Caracteres Sexuais , Sociedades Científicas , Fatores Socioeconômicos , Adulto JovemRESUMO
PURPOSE: Besides the adverse health effects of a low folate intake, the risks of high intakes of folic acid have moved into the focus. The aim of this study was to investigate the potential range of folate and folic acid intake of the German population under consideration of different fortification scenarios. METHODS: Food consumption data of 13,926 participants of the German National Nutrition Survey II (NVS II), collected with two 24-h recalls, were used to calculate the nutrient intake. The nutrient data are based on the German Nutrient Database (BLS), information from a market survey and analyses of multivitamin juices. The scenarios were modelled without, as well as with low and high fortification levels of folic acid. RESULTS: The median intake of dietary folate equivalents ranged from 191 µg/d (men) and 168 µg/d (women) without fortification to 425 µg/d (men) and 334 µg/d (women) in the highest fortification scenario. Thus, 12.4-68.2% (men) and 5.9-56.1% (women) met the 300 µg/d recommended by the nutrition societies of Germany, Austria and Switzerland. In the highest fortification scenario, 1.9% (men) and 0.8% (women) exceeded the tolerable upper intake level (UL) of 1,000 µg/d folic acid given by the European Food Safety Authority. For supplement users, this proportion was 5.2 and 5.4%. CONCLUSIONS: Only a high fortification of several foods leads to a marked increase of the proportion of population reaching the recommendation. Simultaneously, with a high fortification a higher proportion exceeds the UL, especially in combination with supplements.
Assuntos
Ácido Fólico/administração & dosagem , Alimentos Fortificados , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Áustria , Suplementos Nutricionais , Feminino , Alemanha , Humanos , Masculino , Rememoração Mental , Pessoa de Meia-Idade , Inquéritos Nutricionais , Recomendações Nutricionais , Suíça , Adulto JovemRESUMO
PURPOSE: To further characterise the performance of the diet history method and the 24-h recalls method, both in an updated version, a comparison was conducted. METHODS: The National Nutrition Survey II, representative for Germany, assessed food consumption with both methods. The comparison was conducted in a sample of 9,968 participants aged 14-80. Besides calculating mean differences, statistical agreement measurements encompass Spearman and intraclass correlation coefficients, ranking participants in quartiles and the Bland-Altman method. RESULTS: Mean consumption of 12 out of 18 food groups was higher assessed with the diet history method. Three of these 12 food groups had a medium to large effect size (e.g., raw vegetables) and seven showed at least a small strength while there was basically no difference for coffee/tea or ice cream. Intraclass correlations were strong only for beverages (>0.50) and revealed the least correlation for vegetables (<0.20). Quartile classification of participants exhibited more than two-thirds being ranked in the same or adjacent quartile assessed by both methods. For every food group, Bland-Altman plots showed that the agreement of both methods weakened with increasing consumption. CONCLUSIONS: The cognitive effort essential for the diet history method to remember consumption of the past 4 weeks may be a source of inaccurateness, especially for inhomogeneous food groups. Additionally, social desirability gains significance. There is no assessment method without errors and attention to specific food groups is a critical issue with every method. Altogether, the 24-h recalls method applied in the presented study, offers advantages approximating food consumption as compared to the diet history method.
Assuntos
Comportamento Alimentar , Avaliação Nutricional , Inquéritos Nutricionais , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Índice de Massa Corporal , Dieta , Registros de Dieta , Feminino , Alemanha , Humanos , Masculino , Rememoração Mental , Pessoa de Meia-Idade , Fatores Socioeconômicos , Adulto JovemRESUMO
Control of centrosome duplication is tightly linked with the progression of the cell cycle. Recent studies suggest that the fundamental process of centriole duplication is evolutionally conserved. Here, we identified centrosomal P4.1-associated protein (CPAP), a human homologue of SAS-4, as a substrate of PLK2 whose activity oscillates during the cell cycle. PLK2 phosphorylates the S589 and S595 residues of CPAP in vitro and in vivo. This phosphorylation is critical for procentriole formation during the centrosome cycle. PLK4 also phosphorylates S595 of CPAP, but PLK4 phosphorylation is not a critical step in the PLK4 function in procentriole assembly. CPAP is phosphorylated in a cell cycle stage-specific manner, so that its phosphorylation increases at the G1/S transition phase and decreases during the exit of mitosis. Phosphorylated CPAP is preferentially located at the procentriole. Furthermore, overexpression of a phospho-resistant CPAP mutant resulted in the failure to form elongated centrioles. On the basis of these results, we propose that phosphorylated CPAP is involved in procentriole assembly, possibly for centriole elongation. This work demonstrates an example of how procentriole formation is linked to the progression of the cell cycle.
Assuntos
Ciclo Celular/fisiologia , Centríolos/metabolismo , Centrossomo/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Animais , Linhagem Celular , Técnicas de Silenciamento de Genes , Humanos , Proteínas Associadas aos Microtúbulos/genética , Fosforilação , Proteínas Serina-Treonina Quinases/genéticaRESUMO
Polo-like kinases (Plks) perform crucial functions during mitosis, cytokinesis and centriole duplication. Plk2 is activated in early G1 phase and is involved in the reproduction of centrosomes. However, the mechanisms underlying Plk2-induced centriole duplication are incompletely understood. Here, we show that Plk2 directly targets the F-box protein F-box/WD repeat-containing protein 7 (Fbxw7), which is a regulator of the ubiquitin-mediated degradation of cyclin E. Plk2 phosphorylates Fbxw7 on serine 176 and the two proteins form a complex in vitro and in vivo. Phosphorylation of Fbxw7 by Plk2 induces destabilization of the F-box protein resulting in accumulation of cyclin E and increased potential for centriole reproduction. In addition, loss of Fbxw7 in human cells leads to uncontrolled centriole duplication, highlighting the importance of Fbxw7 regulation by Plk2. These findings define a previously unknown Plk2-dependent pathway involved at the onset of S phase and in centrosome duplication.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Centríolos/metabolismo , Proteínas F-Box/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Proteínas de Ciclo Celular/química , Linhagem Celular , Ciclina E/metabolismo , Proteínas F-Box/química , Proteína 7 com Repetições F-Box-WD , Humanos , Fosforilação , Fosfosserina/metabolismo , Ligação Proteica , Proteínas Quinases/metabolismo , Estabilidade Proteica , Ubiquitina-Proteína Ligases/química , UbiquitinaçãoRESUMO
Centriole duplication occurs once per cell cycle and requires Plk4, a member of the Polo-like kinase family. A key component of the centrosome is the γ-tubulin ring complex (γ-TuRC) that nucleates microtubules. GCP6 is a member of the γ-TuRC, but its role in human cells and the regulation of its functions remain unclear. Here we report that depletion of human GCP6 prevents assembly of the γ-TuRC and induces a high percentage of monopolar spindles. These spindles are characterized by a loss of centrosomal γ-tubulin and reduced centriole numbers. We found that GCP6 is localized in the pericentriolar material but also at distal portions of centrioles. In addition, GCP6 is required for centriole duplication and Plk4-induced centriole overduplication. GCP6 interacts with and is phosphorylated by Plk4. Moreover, we find that Plk4-dependent phosphorylation of GCP6 regulates centriole duplication. These data suggest that GCP6 is a target of Plk4 in centriole biogenesis.
Assuntos
Centríolos/fisiologia , Proteínas Associadas aos Microtúbulos/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Linhagem Celular , Centríolos/metabolismo , Centríolos/ultraestrutura , Humanos , Proteínas Associadas aos Microtúbulos/fisiologia , Fosforilação , Fuso Acromático/metabolismo , Tubulina (Proteína)/metabolismoRESUMO
Centrioles play important roles in the assembly of centrosomes and cilia. Centriole duplication occurs once per cell cycle and is dependent on polo-like kinase 4 (PLK4). To prevent centriole amplification, which is a hallmark of cancer, PLK4 protein levels need to be tightly regulated. Here, we show that the Cullin4A/B-DDB1-DCAF1, CRL4DCAF1, E3 ligase targets PLK4 for degradation in human cells. DCAF1 binds and ubiquitylates PLK4 in the G2 phase to prevent premature centriole duplication in mitosis. In contrast to the regulation of PLK4 by SCFß-TrCP, the interaction between PLK4 and DCAF1 is independent of PLK4 kinase activity and mediated by polo-boxes 1 and 2 of PLK4, suggesting that DCAF1 promotes PLK4 ubiquitylation independently of ß-TrCP. Thus, the SCFSlimb/ß-TrCP pathway, targeting PLK4 for ubiquitylation based on its phosphorylation state and CRL4DCAF1, which ubiquitylates PLK4 by binding to the conserved PB1-PB2 domain, appear to be complementary ways to control PLK4 abundance to prevent centriole overduplication.
Assuntos
Centríolos , Ubiquitina , Humanos , Centríolos/metabolismo , Ubiquitina/metabolismo , Proteínas Contendo Repetições de beta-Transducina/genética , Proteínas Contendo Repetições de beta-Transducina/metabolismo , Ciclo Celular , Ubiquitina-Proteína Ligases/genética , Ubiquitina-Proteína Ligases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismoRESUMO
Primary microcephaly is a rare condition in which brain size is substantially diminished without other syndromic abnormalities. Seven autosomal loci have been genetically mapped, and the underlying causal genes have been identified for MCPH1, MCPH3, MCPH5, MCPH6, and MCPH7 but not for MCPH2 or MCPH4. The known genes play roles in mitosis and cell division. We ascertained three families from an Eastern Canadian subpopulation, each with one microcephalic child. Homozygosity analysis in two families using genome-wide dense SNP genotyping supported linkage to the published MCPH4 locus on chromosome 15q21.1. Sequencing of coding exons of candidate genes in the interval identified a nonconservative amino acid change in a highly conserved residue of the centrosomal protein CEP152. The affected children in these two families were both homozygous for this missense variant. The third affected child was compound heterozygous for the missense mutation plus a second, premature-termination mutation truncating a third of the protein and preventing its localization to centrosomes in transfected cells. CEP152 is the putative mammalian ortholog of Drosphila asterless, mutations in which affect mitosis in the fly. Published data from zebrafish are also consistent with a role of CEP152 in centrosome function. By RT-PCR, CEP152 is expressed in the embryonic mouse brain, similar to other MCPH genes. Like some other MCPH genes, CEP152 shows signatures of positive selection in the human lineage. CEP152 is a strong candidate for the causal gene underlying MCPH4 and may be an important gene in the evolution of human brain size.
Assuntos
Proteínas de Ciclo Celular/genética , Microcefalia/genética , Sequência de Aminoácidos , Animais , Sequência de Bases , Biologia Computacional , Feminino , Estudos de Associação Genética , Loci Gênicos , Humanos , Camundongos , Dados de Sequência Molecular , Mutação , LinhagemRESUMO
Plant-based meat substitutes (PBMS) are becoming increasingly popular due to growing concerns about health, animal welfare, and environmental issues associated with animal-based foods. The aim of this study was to compare the declared energy and nutrient contents of PBMS with corresponding meat products and sausages available on the German market. Mandatory nutrition labelling data of 424 PBMS and 1026 meat products and sausages, surveyed in 2021 and 2020, respectively, as part of the German national monitoring of packaged food were used to test for differences in energy and nutrient contents. Principal component analysis (PCA) was used to describe characteristics in the energy and nutrient contents. The comparison showed that most of the PBMS subcategories had significantly lower contents of fat and saturated fat but higher contents of carbohydrate and sugar than corresponding meat subcategories. For salt, the only striking difference was that PBMS salamis had lower salt content than meat salamis. Overall, the PCA revealed protein as a main characteristic for most PBMS categories, with the protein content being equivalent to or, in most protein-based PBMS, even higher than in the corresponding meat products. The wide nutrient content ranges within subcategories, especially for salt, reveal the need and potential for reformulation.