Advances in the research and applications of orange fluorescent protein / 生物工程学报

Fluorescent proteins can be used as probes to investigate intercellular molecular interactions and trace the pathway of specific metabolites, thus providing a detailed and accurate description of various metabolic processes and cellular pathways in living cells. Nowadays, the existing fluorescent proteins cover almost all spectral bands from ultraviolet to far-red. These fluorescent proteins have been applied in many fields of bioscience with the help of high-resolution microscopy, making great contributions to the development of biology. It is generally agreed that orange fluorescent proteins refer to the fluorescent proteins at the spectral range of 540-570 nm. In recent years, researches on orange fluorescent proteins have made great progress, and they have been widely applied in the field of biology and medicine as reporter protein and fluorescence resonance energy transfer as fluorescent receptor. This paper reviews the studies in the field of orange fluorescent proteins over the last 15 years, with the special focus on the development and application of orange fluorescent proteins to provide the basis for the future studies.

On the necessity of an integrative approach to understand protein structural dynamics / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Proteins are dynamic, fluctuating between multiple conformational states. Protein dynamics, spanning orders of magnitude in time and space, allow proteins to perform specific functions. Moreover, under certain conditions, proteins can morph into a different set of conformations. Thus, a complete understanding of protein structural dynamics can provide mechanistic insights into protein function. Here, we review the latest developments in methods used to determine protein ensemble structures and to characterize protein dynamics. Techniques including X-ray crystallography, cryogenic electron microscopy, and small angle scattering can provide structural information on specific conformational states or on the averaged shape of the protein, whereas techniques including nuclear magnetic resonance, fluorescence resonance energy transfer (FRET), and chemical cross-linking coupled with mass spectrometry provide information on the fluctuation of the distances between protein domains, residues, and atoms for the multiple conformational states of the protein. In particular, FRET measurements at the single-molecule level allow rapid resolution of protein conformational states, where information is otherwise obscured in bulk measurements. Taken together, the different techniques complement each other and their integrated use can offer a clear picture of protein structure and dynamics.

Esophageal eosinophilia in pediatric patients with cerebral palsy / Eosinofilia esofágica em pacientes pediátricos com paralisia cerebral

ABSTRACT Objective: To describe the clinical picture, test results, and clinical evolution of patients with cerebral palsy associated with diagnosis of eosinophilic esophagitis, monitored at tertiary centre. Methods: Cross-sectional, retrospective and descriptive study that evaluated the medical records data of pediatric patients with diagnosis of cerebral palsy and eosinophilic esophagitis in a tertiary center of pediatric gastroenterology between August 2005 and August 2013. Results: Seven out of 131 patients with cerebral palsy had the diagnosis of eosinophilic esophagitis. The mean age at diagnosis of eosinophilic esophagitis was 52.3 months and the mean number of eosinophils in esophagus was 35 per high-power field. Symptoms more frequent were recurrent vomiting and disphagia. Endoscopic alterations found were mucosal thickening, vertical lines, mucosal opacificacion and white plaques. Conclusion: The frequency of eosinophilic esophagitis found was higher than in general pediatric population. The investigation of eosinophilic esophagitis should be done regularly in those patients, once this entity could overlap other gastrointestinal diseases. .

RESUMO Objetivo: Descrever quadro clínico, resultados dos exames e evolução clínica de pacientes com paralisia cerebral associada ao diagnóstico de esofagite eosinofílica, monitorados em um centro terciário. Métodos: Estudo transversal, retrospectivo e descritivo, que avaliou os prontuários médicos de pacientes pediátricos com diagnóstico de paralisia cerebral e esofagite eosinofílica, atendidos em um centro terciário de gastrenterologia pediátrica, entre agosto de 2005 e agosto de 2013. Resultados: Dos 131 pacientes com paralisia cerebral, 7 tiveram o diagnóstico de esofagite eosinofílica no período estudado. A idade média no momento do diagnóstico de esofagite eosinofílica foi 52,3 meses, e o número médio de eosinófilos no esôfago foi de 35 por campo de grande aumento. Os sintomas mais frequentes associados foram vômitos recorrentes e disfagia. As alterações endoscópicas encontradas foram espessamento da mucosa, linhas verticais, opacificação da mucosa e as placas esbranquiçadas. Conclusão: A frequência de esofagite eosinofílica encontrada foi maior que na população pediátrica em geral. A investigação de esofagite eosinofílica deve ser realizada regularmente nos pacientes com paralisia cerebral, pois pode haver uma sobreposição de sintomas de outras doenças gastrintestinais. .

Comparison of activity of OsDmc1A recombinase of rice (Oryza sativa) in presence of Ca2+ and Mg2+ ions.

Recombinases are known to play an important role in the homology search and strand exchange during meiosis as well as homologous recombination (HR)-mediated DNA repair specifically require Mg2+ ion for their activity. The Ca2+ has been shown to stimulate the strand exchange activity of hDmc1 and ScDmc1 by forming the extended filaments on DNA. Oryza sativa disrupted meiotic cDNA1A (OsDmc1A), a homologue of yeast and human Dmc1 from rice shows the hallmark functions of recombinase. Here, we report the effects of Ca2+ and Mg2+ on OsDmc1A activity from rice (Oryza sativa). OsDmc1A showed a concentration-dependent binding with both single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) substrates in presence of Mg2+ or Ca2+. The ssDNA and dsDNA binding activities, as well as renaturation activity of OsDmc1A were similar in the presence of Ca2+ or Mg2+. Increasing the Ca2+ or Mg2+ increased the DNA binding, renaturation and strand exchange of OsDmc1A. But, OsDmc1A showed only a slight stimulation of strand exchange activity in presence of Ca2+, when compared the activity in presence of Mg2+. Electron microscopy showed that OsDmc1A formed ring-like structures in presence of Mg2+ or Ca2+. However, OsDmc1A formed filament like structures with both ss and dsDNA in presence of Mg2+ or Ca2+. Taken together, Ca2+ did not affect OsDmc1A recombinase activity significantly.

Comparison of two scales for evaluation of smile and dental attractiveness

OBJECTIVE: To compare the visual analogue scale (VAS) and the simplified Q-sort method used to investigate the highest level of agreement among dentists, orthodontists and laypeople when assessing smile and dental attractiveness. MATERIAL AND METHODS: An album containing 258 photos of 86 individuals with their lips at rest, a slight and broad smile, was assessed by 25 dentists (general clinicians and various specialties), 23 orthodontists and 27 laypeople with regard to smile and dental attractiveness. To this end, both VAS and simplified Q-sort method were used. Agreements were calculated by intraclass correlation coefficient (ICC). RESULTS: For the single measurement between the VAS method and the simplified Q-sort method, all simplified Q-sort rates were higher in all groups. The simplified Q-sort method results ranged between 0.42 and 0.49 while those of the VAS method varied between 0.37 and 0.42. The simplified Q-sort method also presented higher mean measurement values (0.95 and 0.96) in comparison to VAS (0.94 and 0.95). CONCLUSIONS: Both scales may be considered reliable for evaluating smile and dental attractiveness; however, the simplified Q-Sort method presented slightly higher values than the VAS method. .

OBJETIVO: comparar a escala visual analógica (EVA) e o método Q-sort simplificado quanto à maior concordância nas avaliações entre cirurgiões-dentistas, ortodontistas e leigos em atratividade dentária e do sorriso. MÉTODOS: 258 fotografias, provenientes de 86 indivíduos, fotografados com os lábios em repouso, sorriso leve e sorriso amplo, foram avaliadas quanto à atratividade dentária e do sorriso por meio da EVA e do Q-sort simplificado por 25 cirurgiões-dentistas (clínicos gerais e especialidades diversas), 23 Ortodontistas e 27 leigos. As concordâncias foram calculadas pelo Coeficiente de Correlação Intraclasse (ICC). RESULTADOS: para medida única entre a EVA e o método Q-sort simplificado, todas as taxas do Q-sort simplificado foram maiores em todos os grupos. O resultado do Q-sort simplificado variou entre 0,42 e 0,49, e da EVA entre 0,37 e 0,42. O Q-sort simplificado também apresentou valores de medida média superiores (0,95 e 0,96) em relação à EVA (0,94 e 0,95). CONCLUSÃO: pode-se considerar que ambas as escalas são confiáveis para avaliação da atratividade dentária e do sorriso; porém, o método Q-sort simplificado apresentou valores ligeiramente maiores que os da EVA. .

Physical inactivity and anthropometric measures in schoolchildren from Paranavaí, Paraná, Brazil / Inatividade física e medidas antropométricas em escolares de Paranavaí, Paraná, Brasil

OBJECTIVE: To investigate the association between physical inactivity and anthropometric measures in schoolchildren from Paranavaí-Parana, Brazil. METHODS: Cross-sectional survey, carried out in July and August 2013. Sample of 566 students (287 boys and 279 girls) from 6th to 9th grade, aged 10 to 14 years, from public and private schools of Paranavaí - PR, Southern Brazil. The variables analyzed were: time of weekly physical activity through a questionnaire (physical inactivity <300 minutes/week), body mass index (BMI) and waist circumference (WC). In the statistical analysis, the U Mann-Whitney and Student's t tests were used for comparison between genders. To identify factors associated with insufficient levels of physical activity, univariate and multivariate logistic regression analysis was applied and expressed in Odds ratio (OR) and 95% confidence interval (95%CI). RESULTS: There was an association between physical inactivity and anthropometric measurements for BMI (p<0.001) and WC (p<0.001), with a prevalence rate of 56.1% and 52.7% of inactive adolescents, respectively. In the multivariate analysis, there was significant association of physical inactivity and overweight (OR 1.8, 95%CI: 1.1-3.0) and with increased waist circumference (OR 2.8, 95%CI: 1.4-3.8). CONCLUSIONS: Inadequate levels of physical activity is a determining factor for overweight and abdominal adiposity. Accordingly, preventive measures should be taken, especially in schools, emphasizing the importance of exercise for body composition control and weight reduction. .

OBJETIVO: Investigar a associação entre a inatividade física e medidas antropométricas em escolares de Paranavaí, Paraná, Brasil. MÉTODOS: Pesquisa com delineamento transversal, feita em julho e agosto de 2013. Amostra composta por 566 escolares (287 meninos e 278 meninas), de 10 a 14 anos, do 6° ao 9° ano da rede pública e privada de Paranavaí (PR). As variáveis analisadas foram: tempo de atividade física semanal, por meio de questionário (inatividade física: < 300 min/semanal), índice de massa corporal (IMC) e circunferência de cintura (CC). Na análise estatística foram usados os testes U de Mann-Whitney e t de Student para comparar os sexos. Para verificar os fatores associados ao nível insuficiente de atividade física aplicou-se o modelo de regressão logística binária univariada e multivariada, expressa em odds ratio (OR), e intervalo de confiança de 95% (IC95%). RESULTADOS: Houve associação entre inatividade física e as medidas antropométricas para IMC (p<0,001) e CC (p<0,001), com prevalências de 56,1% e 52,7% de inativos, respectivamente. Na análise multivariada, foram observadas associações significativas de inatividade física nos alunos que apresentaram excesso de peso (OR 1,8; IC95%: 1,1-3,0) e circunferência de cintura aumentada (OR 2,2; IC95%: 1,4-3,8). CONCLUSÕES: Nível inadequado de atividade física é fator determinante no excesso de peso e na adiposidade abdominal. Nesse sentido, medidas preventivas devem ser tomadas, principalmente nas escolas, e enfatizar-se a importância do exercício físico no controle da composição corporal e redução do pesoe. .

Predictors of Success in the Treatment of Obstructive Sleep Apnea Syndrome with Mandibular Repositioning Appliance: A Systematic Review

Introduction Obstructive sleep apnea syndrome affects up to 4% of middle-aged men and 2% of adult women. It is associated with obesity. Objective The objective of this article is to review the literature to determine which factors best correlate with treatment success in patients with obstructive sleep apnea syndrome treated with a mandibular repositioning appliance. Data Synthesis A search was performed of the PubMed, Cochrane, Lilacs, Scielo, and Web of Science databases of articles published from January 1988 to January 2012. Two review authors independently collected data and assessed trial quality. Sixty-nine articles were selected from PubMed and 1 from Cochrane library. Of these, 42 were excluded based on the title and abstract, and 27 were retrieved for complete reading. A total of 13 articles and 1 systematic review were considered eligible for further review and inclusion in this study: 6 studies evaluated anthropomorphic and physiologic factors, 3 articles addressed cephalometric and anatomic factors, and 4 studies evaluated variables related to mandibular repositioning appliance design and activation. All the studies evaluated had low to moderate methodologic quality and were not able to support evidence on prediction of treatment success. Conclusion Based on this systematic review on obstructive sleep apnea syndrome treatment, it remains unclear which predictive factors can be used with confidence to select patients suitable for treatment with a mandibular repositioning appliance. .

A more accurate and efficient fluorescent probe of Caspase-8 activity based on flow cytometric fluorescence resonance energy transfer / 药学学报

As a classic fluorescent detect technique, fluorescence resonance energy transfer (FRET) has been widely used in biological researches. Researchers have developed a series of fluorescence detect probes which were based on FRET. Caspase family plays an important role in apoptosis pathway, especially Caspase-8 which located, at the initial of death receptor mediated apoptosis pathway, whose its activation can trigger subsequent precaspases' activation and lead to apoptosis. So it is of great significance to detect the activation of Caspase-8 in apoptosis assay. In this study, a fluorescent probe based on FRET has been designed which can detect the activity change of Caspase-8 in cells. To identify the effectiveness and specificity of the probe, we measure the Caspase-8 activity under the Caspase-8 specifically activated apoptosis inducer RGD-TRAIL with the flow cytometry FRET detection platform. The results show that the probe can respond to the activity change of Caspase-8 in apoptotic cells, and the change can be quantified rapidly by flow cytometry. The study provides a more efficient and convenient detection method of Caspase-8 activity in living cells.

A Novel, Potent, Small Molecule AKT Inhibitor Exhibits Efficacy against Lung Cancer Cells In Vitro / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: Anomalies of Akt regulation, including overexpression in lung cancer, impart resistance to conventional chemotherapy and radiation, thereby implicating this kinase as a therapeutic intervention point. A novel scaffold of Akt inhibitors was developed through virtual screening of chemical databases available at Birla Institute of Technology and Science, Pilani, Hyderabad, based on docking studies using Maestro. A benzothienopyrimidine derivative (BIA-6) was identified as a potential lead molecule that inhibited Akt1 enzyme activity with an IC50 of 256 nM. MATERIALS AND METHODS: BIA-6 was tested for in vitro Akt1 inhibition using a fluorescence resonance energy transfer kit. Anti-proliferative activity was tested in NCI-H460, A549, NCI-H1975, and NCI-H2170 cell lines. The effect of the compound on p-Akt (S473) was estimated. RESULTS: BIA-6 allosterically caused a dose dependent reduction of growth of cell lines with a half maximal growth inhibition (GI50) range of 0.49 muM to 6.6 muM. Cell cycle analysis indicated that BIA-6 caused a G1 phase arrest at < 100 nM but led to apoptosis at higher doses. BIA-6 also exhibited synergism with standard chemotherapeutic agents. CONCLUSION: BIA-6 is a novel, allosteric Akt inhibitor with potent anti-cancer activity in lung cancer cell lines, that effectively blocks the phosphoinositide-3 kinase/Akt pathway with a high margin selectivity towards normal cells.

Development of sandwich-form biosensor to detect Mycobacterium tuberculosis complex in clinical sputum specimens

Mycobacterium tuberculosis, the causing agent of tuberculosis, comes second only after HIV on the list of infectious agents slaughtering many worldwide. Due to the limitations behind the conventional detection methods, it is therefore critical to develop new sensitive sensing systems capable of quick detection of the infectious agent. In the present study, the surface modified cadmium-telluride quantum dots and gold nanoparticles conjunct with two specific oligonucleotides against early secretory antigenic target 6 were used to develop a sandwich-form fluorescence resonance energy transfer-based biosensor to detect M. tuberculosis complex and differentiate M. tuberculosis and M. bovis Bacille Calmette–Guerin simultaneously. The sensitivity and specificity of the newly developed biosensor were 94.2% and 86.6%, respectively, while the sensitivity and specificity of polymerase chain reaction and nested polymerase chain reaction were considerably lower, 74.2%, 73.3% and 82.8%, 80%, respectively. The detection limits of the sandwich-form fluorescence resonance energy transfer-based biosensor were far lower (10 fg) than those of the polymerase chain reaction and nested polymerase chain reaction (100 fg). Although the cost of the developed nanobiosensor was slightly higher than those of the polymerase chain reaction-based techniques, its unique advantages in terms of turnaround time, higher sensitivity and specificity, as well as a 10-fold lower detection limit would clearly recommend this test as a more appropriate and cost-effective tool for large scale operations.

Study of TGF-β/Smad3 signal pathway using the technology of flurorescence resonance energy transfer / 生物医学工程学杂志

The transforming growth factor-β1 (TGF-β1)/Smad3 signal pathway is related to mutiple physiological and pathological generation mechanism of human being. Up to date, however, the spacial and time information on the phosphorylated Smad3 is still unclear. In this study, the process of Smad3 phosphorylation was observed under the physiological state in the living cells. Firstly, the ECFP-Smad3-Citrine (Smad3 biosensor) fusion protein expression vector was constructed and identified. Then the Smad3 biosensor was transfected into 293T cells. The transfection efficiency and the expressions of fusion proteins were observed in 24 hours. Thirdly, Smad3 biosensor flurorescence resonance energy transfer (FRET) was observed with the inversion fluorescence microscope and measured by the MetaFlour FRET 4. 6 software. Smad3 biosensor transfection efficiency was nearly 40% and the fusion protein was seen under the fluorescence microscope. The FRET ratio of Smad3 biosensor in living 293T cells was decreased after 10 minutes incubation with the ligand of TGF-β1. The period of decreasing CFP and enhancing Citrine signals was about 300 seconds. With the technology of FRET, the TGF-β1/Smad3 signal pathway could be real time monitored dynamically under the physiological condition in living cells.

Research methods in protein-protein and protein-nucleic acid interactions and application in the study of human enterovirus A71 / 病毒学报

Methods for analyses of protein-protein interactions include: yeast two hybrid (Y2H), phage dis- play (PD), co-immunoprecipitation (Co-IP), glutathione S-transferase pull-down (GST pull-down), cellular co-localization, far-western blotting, virus overlay protein binding assay (VOPBA), surface plasmon resonance (SPR), and fluorescence resonance energy transfer (FRET). Technologies for the detection of protein-nucleic acid interactions include: yeast one hybrid (Y1H), chromatin immunoprecipitation (ChIP), electrophoretic mobility shift assay (EMSA), Southwestern blotting, reporter gene, Co-IP, GST pull-down, and PD. These methods are often used in the study of the human enterovirus A71 (EV-A71) by our research team. Reviews in the Chinese literature in this field are lacking, so we reviewed applications of these methods in the study of EV-A71. This review may impart important knowledge in the research of other viruses with regard to protein-protein and protein-nucleic acid interactions.

Applications of FRET technology in the study of mechanotransduction / 生物医学工程学杂志

Mechanical force has essential effects on cellular behaviors such as proliferation, migration and differentiation, and the mechanism of mechanotransduction is still one of the hot spots in mechanobiology study. Traditional methods could not provide accurate evaluation of the protein activation signal upon mechanical stress application. The development of fluorescence protein technology greatly promoted the understanding of mechanotransduction. In particular, genetically-encoded biosensors based on fluorescence resonance energy transfer (FRET) technique has achieved a real-time dynamic observation of living cell signal protein activity, which provides a powerful tool for the in-depth study of biomechanics. In this paper, we provide a summary on recent progress of FRET application in biomechanics. Firstly we introduce the FRET technology, and then we summarize three methods to integrate the mechanical stimulation with the FRET imaging system on cell experiments. After that, the important progress of biomechanical research on signal pathway made by FRET technology, such as cytoskeleton, Rho family, calcium and cellular physical stress visualization, are also discussed. Finally, we point out the bottleneck of the future development in FRET technology, and also make the prospect of the application of FRET in mechanotransduction. In summary, FRET technology provides a powerful tool for the studies of mechanotransduction, which will advance our systematic understanding on the molecular mechanisms about how cells respond to mechanical stimulation.

Plasma membrane calcium ATPase 4b inhibits nitric oxide generation through calcium-induced dynamic interaction with neuronal nitric oxide synthase

The activation and deactivation of Ca(2+)- and calmodulindependent neuronal nitric oxide synthase (nNOS) in the central nervous system must be tightly controlled to prevent excessive nitric oxide (NO) generation. Considering plasma membrane calcium ATPase (PMCA) is a key deactivator of nNOS, the present investigation aims to determine the key events involved in nNOS deactivation of by PMCA in living cells to maintain its cellular context. Using time-resolved Förster resonance energy transfer (FRET), we determined the occurrence of Ca(2+)-induced protein-protein interactions between plasma membrane calcium ATPase 4b (PMCA4b) and nNOS in living cells. PMCA activation significantly decreased the intracellular Ca(2+) concentrations ([Ca(2+)]i), which deactivates nNOS and slowdowns NO synthesis. Under the basal [Ca(2+)]i caused by PMCA activation, no protein-protein interactions were observed between PMCA4b and nNOS. Furthermore, both the PDZ domain of nNOS and the PDZ-binding motif of PMCA4b were essential for the protein-protein interaction. The involvement of lipid raft microdomains on the activity of PMCA4b and nNOS was also investigated. Unlike other PMCA isoforms, PMCA4 was relatively more concentrated in the raft fractions. Disruption of lipid rafts altered the intracellular localization of PMCA4b and affected the interaction between PMCA4b and nNOS, which suggest that the unique lipid raft distribution of PMCA4 may be responsible for its regulation of nNOS activity. In summary, lipid rafts may act as platforms for the PMCA4b regulation of nNOS activity and the transient tethering of nNOS to PMCA4b is responsible for rapid nNOS deactivation.

An open conformation determined by a structural switch for 2A protease from coxsackievirus A16

Coxsackievirus A16 belongs to the family Picornaviridae, and is a major agent of hand-foot-and-mouth disease that infects mostly children, and to date no vaccines or antiviral therapies are available. 2A protease of enterovirus is a nonstructural protein and possesses both self-cleavage activity and the ability to cleave the eukaryotic translation initiation factor 4G. Here we present the crystal structure of coxsackievirus A16 2A protease, which interestingly forms hexamers in crystal as well as in solution. This structure shows an open conformation, with its active site accessible, ready for substrate binding and cleavage activity. In conjunction with a previously reported "closed" state structure of human rhinovirus 2, we were able to develop a detailed hypothesis for the conformational conversion triggered by two "switcher" residues Glu88 and Tyr89 located within the bll2-cII loop. Substrate recognition assays revealed that amino acid residues P1', P2 and P4 are essential for substrate specificity, which was verified by our substrate binding model. In addition, we compared the in vitro cleavage efficiency of 2A proteases from coxsackievirus A16 and enterovirus 71 upon the same substrates by fluorescence resonance energy transfer (FRET), and observed higher protease activity of enterovirus 71 compared to that of coxsackievirus A16. In conclusion, our study shows an open conformation of coxsackievirus A16 2A protease and the underlying mechanisms for conformational conversion and substrate specificity. These new insights should facilitate the future rational design of efficient 2A protease inhibitors.

Realgar-induced apoptosis of cervical cancer cell line Siha via cytochrome c release and caspase-3 and caspase-9 activation / 中国结合医学杂志

<p><b>OBJECTIVE</b>To explore the molecular mechanism of realgar-induced apoptosis of cervical cancer cells.</p><p><b>METHODS</b>The cervical cancer cell line Siha was used to determine the cell viability and apoptosis after treatment with realgar using MTT assay and flow cytometry. The activities of caspase-3, -8, and -9 were detected by fluorescence resonance energy transfer technology and colorimetric assay, while the levels of Bcl-2, cytochrome c, and Bax were detected by Western blot method.</p><p><b>RESULTS</b>Induction of apoptosis by realgar was detected in Siha cell line in a dose-dependent manner. The apoptosis was accompanied by a significant increase in cytochrome c release and activation of caspase-3 and caspase-9 but not caspase-8. Further, the realgar-induced apoptosis was inhibited by a broad-spectrum caspase inhibitor, a caspase-3 inhibitor, and a caspase-9 inhibitor but not by a caspase-8 inhibitor. Bcl-2 and Bax protein expressions were not changed by realgar.</p><p><b>CONCLUSION</b>The induction of apoptosis by realgar is mediated through a cytochrome c-dependent pathway, which sequentially activates caspase-9 and caspase-3.</p>

Structural insights into the assembly of human translesion polymerase complexes

In addition to DNA repair pathways, cells utilize translesion DNA synthesis (TLS) to bypass DNA lesions during replication. During TLS, Y-family DNA polymerase (Polη, Polκ, Polı and Rev1) inserts specific nucleotide opposite preferred DNA lesions, and then Polζ consisting of two subunits, Rev3 and Rev7, carries out primer extension. Here, we report the complex structures of Rev3-Rev7-Rev1(CTD) and Rev3-Rev7-Rev1(CTD)-Polκ(RIR). These two structures demonstrate that Rev1(CTD) contains separate binding sites for Polκ and Rev7. Our BIAcore experiments provide additional support for the notion that the interaction between Rev3 and Rev7 increases the affinity of Rev7 and Rev1. We also verified through FRET experiment that Rev1, Rev3, Rev7 and Polκ form a stable quaternary complex in vivo, thereby suggesting an efficient switching mechanism where the "inserter" polymerase can be immediately replaced by an "extender" polymerase within the same quaternary complex.

Molecular detection of Schistosoma japonicum in infected snails and mouse faeces using a real-time PCR assay with FRET hybridisation probes

A real-time polymerase chain reaction (PCR) assay with fluorescence resonance energy transfer (FRET) hybridisation probes combined with melting curve analysis was developed to detect Schistosoma japonicum in experimentally infected snails and in faecal samples of infected mice. This procedure is based on melting curve analysis of a hybrid between an amplicon from the S. japonicum internal transcribed spacer region 2 sequence, which is a 192-bp S. japonicum-specific sequence, and fluorophore-labelled specific probes. Real-time FRET PCR could detect as little as a single cercaria artificially introduced into a pool of 10 non-infected snails and a single egg inoculated in 100 mg of non-infected mouse faeces. All S. japonicum-infected snails and all faecal samples from infected mice were positive. Non-infected snails, non-infected mouse faeces and genomic DNA from other parasites were negative. This assay is rapid and has potential for epidemiological S. japonicum surveys in snails, intermediate hosts and faecal samples of final hosts.

Establishment and application of high throughput screening model for hepatitis C virus NS3-4A protease inhibitors in vitro / 中国医学科学院学报

<p><b>OBJECTIVE</b>To establish fluorescence resonance energy transfer (FRET) assay method of detecting proteolytic activity of non-structural protein 3-4A (NS3-4A) serine protease of hepatitis C virus (HCV) for high throughput screening inhibitors against HCV in vitro.</p><p><b>METHODS</b>HCV recombinant plasmid pMAL~c2/NS3-4A was transformed into the E.coli strain K12TB1. Maltose-binding-protein (MBP) NS3-4A fusion protein expression was induced by adding isopropyl-β-D-thiogalacto-pyranoside (IPTG) and purified by affinity chromatography. The proteolytic activity of MBP-NS3-4A protease was analyzed by FRET with the special protease substrate. The reaction system in this model was optimized, and the reliability of the model was evaluated.</p><p><b>RESULTS</b>High throughput screening model for HCV NS3-4A protease inhibitors was established, and the best concentrations of enzyme and substrate were optimized. In the model, the Km value of protease was 4.74 μmol/L, Z factor was up to 0.80, and coefficient of variation (CV) was 1.91%. BILN 2061, one of the known HCV protease inhibitors, was measured with the Ki of 0.30 nmol/L.</p><p><b>CONCLUSION</b>The assay model using FRET method for HCV NS3 4A serine protease is stable and reliable, and the model is suitable for high throughput screening for HCV NS3 4A protease inhibitors.</p>