Objective Bloom’s syndrome is an autosomal recessive disorder characterized by genomic instability and a predisposition to many cancers. Mutations of the BLM gene (encoding a BLM helicase) may form a structure of t...Objective Bloom’s syndrome is an autosomal recessive disorder characterized by genomic instability and a predisposition to many cancers. Mutations of the BLM gene (encoding a BLM helicase) may form a structure of the etiology of this disease. As a global pollutant, mercury poses a major threat to human health. The current study was conducted to elucidate the effects of Hg^2+ on the structure and activity of BLM642‐1290 recombinant helicase, and to further explore the molecular mechanisms of mercury toxicity to the DNA helicase. Methods The effects of Hg^2+ on biological activity and structure of BLM642‐1290 recombinant helicase were determined by fluorescence polarized, ultraviolet spectroscopic, and free‐phosphorus assay technologies, respectively. Results The helicase activity, the DNA‐binding activity, and the ATPase activity of BLM642‐1290 recombinant helicase were inhibited by Hg^2+ treatment. The LMCT (ligand‐to‐metal charge transition) peaks of the helicase were enhanced with the increase of the Hg^2+ level. The LMCT peaks of the same concentration of helicase gradually increased over time. Conclusions The biological activity of BLM642‐1290 recombinant helicase is inhibited by Hg^2+ treatment. The conformation of the helicase is significantly altered by Hg^2+ . There exist two binding sites between Hg^2+ and the helicase, which are located in the amino acid residues 1063‐1066 and 940‐944 of the helicase, respectively.展开更多
Objective To study the effect of fleroxacin (FLRX) on biological properties of Bloom (BLM) helicase catalytic core (BLM 642-2290 helicase) in vitro and the molecular mechanism of interaction between the two mol...Objective To study the effect of fleroxacin (FLRX) on biological properties of Bloom (BLM) helicase catalytic core (BLM 642-2290 helicase) in vitro and the molecular mechanism of interaction between the two molecules. Methods DNA-binding and unwinding activities of BLM 642-1290 helicase were assayed by fluorescence polarization and gel retardation assay under conditions that the helicase was subjected to different concentrations of FLRX. Effect of FLRX on helicase ATPase activity was analyzed by phosphorus-free assay based on a colorimetric estimation of ATP hydrolysis-produced inorganic phosphate. Molecular mechanism of interaction between the two molecules was assayed by ultraviolet and fluorescence spectra. Results The DNA unwinding and ATPase activities of BLM 642-1290 helicase were inhibited whereas the DNA-binding activity was promoted in vitro. A BLM-FLRX complex was formed through one binding site, electrostatic and hydrophobic interaction force. Moreover, the intrinsic fluorescence of the helicase was quenched by FLRX as a result of non-radioactive energy transfer. The biological activity of helicase was affected by FLRX, which may be through an allosteric mechanism and stabilization of enzyme conformation in low helicase activity state, disruption of the coupling of ATP hydrolysis to unwinding, and blocking helicase translocation on DNA strands. Conclusion FLRX may affect the biological activities and conformation of BLM 642-1290 helicase, and DNA helicase may be used as a promising drug target for some diseases.展开更多
Recently emerged SARS-CoV-2 caused a major outbreak of coronavirus disease 2019(COVID-19)and instigated a widespread fear,threatening global health safety.To date,no licensed antiviral drugs or vaccines are available ...Recently emerged SARS-CoV-2 caused a major outbreak of coronavirus disease 2019(COVID-19)and instigated a widespread fear,threatening global health safety.To date,no licensed antiviral drugs or vaccines are available against COVID-19 although several clinical trials are under way to test possible therapies.During this urgent situation,computational drug discovery methods provide an alternative to tiresome high-throughput screening,particularly in the hit-to-lead-optimization stage.Identification of small molecules that specifically target viral replication apparatus has indicated the highest potential towards antiviral drug discovery.In this work,we present potential compounds that specifically target SARS-CoV-2 vital proteins,including the main protease,Nsp12 RNA polymerase and Nsp13 helicase.An integrative virtual screening and molecular dynamics simulations approach has facilitated the identification of potential binding modes and favourable molecular interaction profile of corresponding compounds.Moreover,the identification of structurally important binding site residues in conserved motifs located inside the active site highlights relative importance of ligand binding based on residual energy decomposition analysis.Although the current study lacks experimental validation,the structural information obtained from this computational study has paved way for the design of targeted inhibitors to combat COVID-19 outbreak.展开更多
Objective:Hepatocellular carcinoma(HCC),the main type of liver cancer,has a high morbidity and mortality,and a poor prognosis.RNA helicase DDX5,which acts as a transcriptional co-regulator,is overexpressed in most mal...Objective:Hepatocellular carcinoma(HCC),the main type of liver cancer,has a high morbidity and mortality,and a poor prognosis.RNA helicase DDX5,which acts as a transcriptional co-regulator,is overexpressed in most malignant tumors and promotes cancer cell growth.Heat shock protein 90(HSP90)is an important molecular chaperone in the conformational maturation and stabilization of numerous proteins involved in cell growth or survival.Methods:DDX5 m RNA and protein expression in surgically resected HCC tissues from 24 Asian patients were detected by quantitative real-time PCR and Western blot,respectively.The interaction of DDX5-HSP90 was determined by molecular docking,immunoprecipitation,and laser scanning confocal microscopy.The autophagy signal was detected by Western blot.The cell functions and signaling pathways of DDX5 were determined in 2 HCC cell lines.Two different murine HCC xenograft models were used to determine the function of DDX5 and the therapeutic effect of an HSP90 inhibitor.Results:HSP90 interacted directly with DDX5 and inhibited DDX5 protein degradation in the AMPK/ULK1-regulated autophagy pathway.The subsequent accumulation of DDX5 protein induced the malignant phenotype of HCC by activating theβ-catenin signaling pathway.The silencing of DDX5 or treatment with HSP90 inhibitor both blocked in vivo tumor growth in a murine HCC xenograft model.High levels of HSP90 and DDX5 protein were associated with poor prognoses.Conclusions:HSP90 interacted with DDX5 protein and subsequently protected DDX5 protein from AMPK/ULK1-regulated autophagic degradation.DDX5 and HSP90 are therefore potential therapeutic targets for HCC.展开更多
P68 RNA helicase is a prototypical DEAD box RNA helicase. The protein plays a very important role in early organ development and maturation. Consistent with the function of the protein in transcriptional regulation an...P68 RNA helicase is a prototypical DEAD box RNA helicase. The protein plays a very important role in early organ development and maturation. Consistent with the function of the protein in transcriptional regulation and pre-mRNA splicing, p68 was found to predominately localize in the cell nucleus. However, recent experiments demon- strate a transient cytoplasmic localization of the protein. We report here that p68 shuttles between the nucleus and the cytoplasm. The nucleocytoplasmic shuttling of p68 is mediated by two nuclear localization signal and two nuclear exporting signal sequence elements. Our experiments reveal that p68 shuttles via a classical RanGTPase-dependent pathway.展开更多
The current therapeutic regimen to combat chronic hepatitis C is not optimal due to substantial side effects and the failure of a significant proportion of patients to achieve a sustained virological response. Recentl...The current therapeutic regimen to combat chronic hepatitis C is not optimal due to substantial side effects and the failure of a significant proportion of patients to achieve a sustained virological response. Recently developed direct-acting antivirals targeting hepatitis C virus (HCV) enzymes reportedly increase the virologic response to therapy but may lead to a selection of drug-resistant variants. Besides direct-acting antivirals, another promising class of HCV drugs in development include host targeting agents that are responsible for interfering with the host factors crucial for the viral life cycle. A family of host proteins known as DEAD-box RNA helicases, characterized by nine conserved motifs, is known to play an important role in RNA metabolism. Several members of this family such as DDX3, DDX5 and DDX6 have been shown to play a role in HCV replication and this review will summarize our current knowledge on their interaction with HCV. As chronic hepatitis C is one of the leading causes of hepatocellular carcinoma, the involvement of DEAD-box RNA helicases in the development of HCC will also be highlighted. Continuing research on the interaction of host DEAD-box proteins with HCV and the contribution to viral replication and pathogenesis could be the panacea for the development of novel therapeutics against HCV.展开更多
Flaviviruses are positive-sense RNA viruses, and many are important human pathogens. Nonstructural protein 2B and 3 of the flaviviruses(NS2BNS3) form an endoplasmic reticulum(ER) membrane-associated hetero-dimeric com...Flaviviruses are positive-sense RNA viruses, and many are important human pathogens. Nonstructural protein 2B and 3 of the flaviviruses(NS2BNS3) form an endoplasmic reticulum(ER) membrane-associated hetero-dimeric complex through the NS2B transmembrane region. The NS2BNS3 complex is multifunctional. The N-terminal region of NS3, and its cofactor NS2B fold into a protease that is responsible for viral polyprotein processing, and the C-terminal domain of NS3 possesses NTPase/RNA helicase activities and is involved in viral RNA replication and virus particle formation. In addition, NS2BNS3 complex has also been shown to modulate viral pathogenesis and the host immune response. Because of the essential functions that the NS2BNS3 complex plays in the flavivirus life cycle, it is an attractive target for antiviral development. This review focuses on the recent biochemical and structural advances of NS2BNS3 and provides a brief update on the current status of drug development targeting this viral protein complex.展开更多
RecQ is a highly conserved helicase necessary for maintaining genome stability in all organisms. Genome comparison showed that a homologue of RecQ in Deinococcus radiodurans designated as DR1289 is a member of RecQ fa...RecQ is a highly conserved helicase necessary for maintaining genome stability in all organisms. Genome comparison showed that a homologue of RecQ in Deinococcus radiodurans designated as DR1289 is a member of RecQ family with unusual domain arrangement: a helicase domain, an RecQ C-terminal domain, and surprisingly three HRDC domain repeats, whose func-tion, however, remains obscure currently. Using an insertion deletion, we discovered that the DRRecQ mutation causes an increase in gamma radiation, hydroxyurea and mitomycine C and UV sensitivity. Using the shuttle plasmid pRADK, we complemented various domains of the D. radiodurans RecQ (DRRecQ) to the mutant in vivo. Results suggested that both the helicase and helicase-and-RNase-D-C-terminal (HRDC) domains are essential for complementing several phenotypes. The complementation and biochemical function of DRRecQ variants with different domains truncated in vitro suggested that both the helicase and three HRDC domains are necessary for RecQ functions in D. radiodurans, while three HRDC domains have a synergistic effect on the whole function. Our finding leads to the hypothesis that the RecF recombination pathway is likely a primary path of double strand break repair in this well-known radioresistant organism.展开更多
Grapevine growing areas are increasingly affected by drought,which has greatly limited global wine production and quality.DEAD-box is one of the largest subfamilies of the RNA helicase family,and its members play key ...Grapevine growing areas are increasingly affected by drought,which has greatly limited global wine production and quality.DEAD-box is one of the largest subfamilies of the RNA helicase family,and its members play key roles in the growth and development of plants and their stress responses.Previous studies have shown the potential of DEAD-box genes in the drought stress responses of Arabidopsis and tomato,rice,and other crop species.However,information about DEAD-box genes in grapevine remains limited.In this report,a total of 40 DEAD-box genes were identified in grapevine and their protein sequence characteristics and gene structures were analyzed.By comparing the expression profiles of VviDEADRHs in response to drought stress in different grapevine varieties,nine candidate genes(VviDEADRH10c,-13,-22,-25a,-25b,-33,-34,-36,and-39)were screened based on expression profiling data.Combined with qRTPCR results,Vvi DEADRH25a was selected for functional verification.Heterologous overexpression of Vvi DEADRH25a in Arabidopsis showed the transgenic plants were more sensitive to drought stress than the control.Both electrolyte permeability and malondialdehyde content were significantly increased in transgenic plants,whereas the chlorophyll content and superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),and ascorbate peroxidase(APX)enzyme activities were significantly decreased.Furthermore,VviDEADRH25a-overexpressing plants showed down-regulated expression levels of several drought stress-related marker genes,namely At COR15a,At RD29A,At ERD15,and At P5CS1,which indicated that they participated in the drought stress response.In summary,this study provides new insights into the structure,evolution,and participation of DEAD-box RNA helicase genes in the response to drought stress in grapevines.展开更多
Pancreatic cancer is one of the deadliest cancers with a very poor prognosis. Recently, there has been a significant increase in research directed towards identifying potential biomarkers that can be used to diagnose ...Pancreatic cancer is one of the deadliest cancers with a very poor prognosis. Recently, there has been a significant increase in research directed towards identifying potential biomarkers that can be used to diagnose and provide prognostic information for pancreatic cancer. These markers can be used clinically to optimize and personalize therapy for individual patients. In this review, we focused on 3 biomarkers involved in the DNA damage response pathway and the necroptosis pathway: Chromodomainhelicase-DNA binding protein 5, chromodomain-helicaseDNA binding protein 7, and mixed lineage kinase domain-like protein. The aim of this article is to review present literature provided for these biomarkers and current studies in which their effectiveness as prognostic biomarkers are analyzed in order to determine their future use as biomarkers in clinical medicine. Based on the data presented, these biomarkers warrant further investigation,and should be validated in future studies.展开更多
OBJECTIVE To evaluate if RNA helicase DDX20,highly expressed in triple negative breast cancer(TNBC)cells,could serve as a surrogate marker for simvastatin treatment response.METHODS We first assessed correlation betwe...OBJECTIVE To evaluate if RNA helicase DDX20,highly expressed in triple negative breast cancer(TNBC)cells,could serve as a surrogate marker for simvastatin treatment response.METHODS We first assessed correlation between 17 mevalonate pathway-related genes and expression of DDX20 in a cohort of 1325 breast cancer tumors.TNBC cells,MDA-MB-231,were then treated with simvastatin and mevalonate pathway intermediates to assess the alteration in DDX20 expression.In the mouse model,MDA-MB-231 cells were injected to tail veins of mice,groups of 8mice each were injected intraperioneally with vehicle or simvastatin 25mg·kg-1 3times a week for 6weeks.The number of metastatic colonies formed was quantified and immunohistochemical(IHC)staining of DDX20 was carried out in the lung tissues.RESULTS Among the 17 genes evaluated,positive correlation with DDX20 expression was observed in eight of them,with HMGCR having the highest correlation.Our in vitro experiments show exposure of breast cancer cells to simvastatin lead to a Rho-dependent decrease in gene expression of DDX20,leading to decreased tumor proliferation in a mevalonate pathway-dependent manner.Conversely,ectopic overexpression of DDX20 significantly abrogated the anti-metastatic activity of simvastatin.A similar observation is seen in the mouse model,where simvastatin-injected mice show significantly fewer visible lung metastases compared to placebo-fed mice.IHC staining on these lung tissues showed decreased DDX20 expression in simvastatin-injected group,corroborating our observations in vitro.CONCLUSION DDX20 is a potential surrogate marker for simvastatin treatment response in breast cancer and a long term implication of our findings is the possibility of an effective combinatorial therapeutic intervention using statins(to suppress DDX20 gene expression)and a suitable firstline agent″for the kill″of invasive breast cancer.展开更多
RecQ5β is an essential DNA helicase in humans, playing important roles in DNA replication, repair, recombination and transcription. The unwinding activity and substrate specificity of RecQ5β is still elusive. Here, ...RecQ5β is an essential DNA helicase in humans, playing important roles in DNA replication, repair, recombination and transcription. The unwinding activity and substrate specificity of RecQ5β is still elusive. Here, we used stopped-flow kinetic method to measure the unwinding and dissociation kinetics of RecQ5β with several kinds of DNA substrates, and found that RecQ5β could well unwind ss/ds DNA, forked DNA and Holiday junction, but was compromised in unwinding blunt DNA and G-quadruplex. Rec5β has the preferred unwinding specificity for certain DNA substrates containing the junction point, which may improve the binding affinity and unwinding activity of RecQ5β. Moreover, from a comparison with the truncated RecQ5β~(1-467), we discovered that the C-terminal domain might strongly influence the unwinding activity and binding affinity of RecQ5β. These results may shed light on the physiological functions and working mechanisms of RecQ5β helicase.展开更多
Hepatitis C virus(HCV)helicase is a molecular motor that splits nucleic acid duplex structures during viral replication,therefore representing a promising target for antiviral treatment.Hence,a detailed understanding ...Hepatitis C virus(HCV)helicase is a molecular motor that splits nucleic acid duplex structures during viral replication,therefore representing a promising target for antiviral treatment.Hence,a detailed understanding of the mechanism by which it operates would facilitate the development of efficient drug-assisted therapies aiming to inhibit helicase activity.Despite extensive investigations performed in the past,a thorough understanding of the activity of this important protein was lacking since the underlying internal conformational motions could not be resolved.Here we review investigations that have been previously performed by us for HCV helicase.Using methods of structure-based computational modelling it became possible to follow entire operation cycles of this motor protein in structurally resolved simulations and uncover the mechanism by which it moves along the nucleic acid and accomplishes strand separation.We also discuss observations from that study in the light of recent experimental studies that confirm our findings.展开更多
猪肺炎支原体的持续性感染问题频发,同源重组介导的抗原变异扮演重要角色。解螺旋酶RuvA调节霍利迪连接体变构是参与同源重组的关键步骤。鉴于此,本研究旨在原核表达猪肺炎支原体解螺旋酶RuvA重组蛋白,鉴定其DNA结合活性并制备多克隆抗...猪肺炎支原体的持续性感染问题频发,同源重组介导的抗原变异扮演重要角色。解螺旋酶RuvA调节霍利迪连接体变构是参与同源重组的关键步骤。鉴于此,本研究旨在原核表达猪肺炎支原体解螺旋酶RuvA重组蛋白,鉴定其DNA结合活性并制备多克隆抗体。试验通过分子克隆构建原核表达质粒pET21a-RuvA,经诱导表达和纯化获得RuvA M hp重组蛋白;免疫家兔制备抗RuvA M hp多克隆抗体,再利用间接ELISA和Western blot试验进行效价测定和特异性验证;利用凝胶迁移试验结合表面等离子共振技术分析RuvA M hp的DNA结合活性;利用凝胶迁移试验结合Western blot试验鉴定RuvA M hp的寡聚特性。结果显示:原核表达的RuvA M hp重组蛋白约为26 ku;制备的抗RuvA M hp多克隆抗体效价为1∶256000,且具有良好的特异性;RuvA M hp具有较强的DNA结合活性,对霍利迪连接体的亲和力高达624.4 pmol·L^(-1)(K D),并且主要以八聚体形式与其形成稳定复合物。通过RuvA M hp的原核表达、多克隆抗体制备及活性鉴定,为后续探索RuvA调解同源重组介导猪肺炎支原体抗原变异的分子机制奠定了基础。展开更多
基金supported by the Natural Sciences Foundation of China (NSFC, No.30660043)the National Basic Research Program of China (2010CB534912)+1 种基金the Doctoral Program of the Ministry of Education of China (No.200806570003)the Governor Talents Foundation of Guizhou Province (No.200822)
文摘Objective Bloom’s syndrome is an autosomal recessive disorder characterized by genomic instability and a predisposition to many cancers. Mutations of the BLM gene (encoding a BLM helicase) may form a structure of the etiology of this disease. As a global pollutant, mercury poses a major threat to human health. The current study was conducted to elucidate the effects of Hg^2+ on the structure and activity of BLM642‐1290 recombinant helicase, and to further explore the molecular mechanisms of mercury toxicity to the DNA helicase. Methods The effects of Hg^2+ on biological activity and structure of BLM642‐1290 recombinant helicase were determined by fluorescence polarized, ultraviolet spectroscopic, and free‐phosphorus assay technologies, respectively. Results The helicase activity, the DNA‐binding activity, and the ATPase activity of BLM642‐1290 recombinant helicase were inhibited by Hg^2+ treatment. The LMCT (ligand‐to‐metal charge transition) peaks of the helicase were enhanced with the increase of the Hg^2+ level. The LMCT peaks of the same concentration of helicase gradually increased over time. Conclusions The biological activity of BLM642‐1290 recombinant helicase is inhibited by Hg^2+ treatment. The conformation of the helicase is significantly altered by Hg^2+ . There exist two binding sites between Hg^2+ and the helicase, which are located in the amino acid residues 1063‐1066 and 940‐944 of the helicase, respectively.
基金supported by the National Basic Research Program of China (No.2010CB534912)the Doctoral Program of the Ministry of Education (No.200806570003)+1 种基金the Governor of Guizhou Province Talents Fund (No.200822)Guizhou University innovation fundsfor graduate student (No. Nongke 2012027)
文摘Objective To study the effect of fleroxacin (FLRX) on biological properties of Bloom (BLM) helicase catalytic core (BLM 642-2290 helicase) in vitro and the molecular mechanism of interaction between the two molecules. Methods DNA-binding and unwinding activities of BLM 642-1290 helicase were assayed by fluorescence polarization and gel retardation assay under conditions that the helicase was subjected to different concentrations of FLRX. Effect of FLRX on helicase ATPase activity was analyzed by phosphorus-free assay based on a colorimetric estimation of ATP hydrolysis-produced inorganic phosphate. Molecular mechanism of interaction between the two molecules was assayed by ultraviolet and fluorescence spectra. Results The DNA unwinding and ATPase activities of BLM 642-1290 helicase were inhibited whereas the DNA-binding activity was promoted in vitro. A BLM-FLRX complex was formed through one binding site, electrostatic and hydrophobic interaction force. Moreover, the intrinsic fluorescence of the helicase was quenched by FLRX as a result of non-radioactive energy transfer. The biological activity of helicase was affected by FLRX, which may be through an allosteric mechanism and stabilization of enzyme conformation in low helicase activity state, disruption of the coupling of ATP hydrolysis to unwinding, and blocking helicase translocation on DNA strands. Conclusion FLRX may affect the biological activities and conformation of BLM 642-1290 helicase, and DNA helicase may be used as a promising drug target for some diseases.
基金This study was supported by IRO scholarship Ph.D.Grant.
文摘Recently emerged SARS-CoV-2 caused a major outbreak of coronavirus disease 2019(COVID-19)and instigated a widespread fear,threatening global health safety.To date,no licensed antiviral drugs or vaccines are available against COVID-19 although several clinical trials are under way to test possible therapies.During this urgent situation,computational drug discovery methods provide an alternative to tiresome high-throughput screening,particularly in the hit-to-lead-optimization stage.Identification of small molecules that specifically target viral replication apparatus has indicated the highest potential towards antiviral drug discovery.In this work,we present potential compounds that specifically target SARS-CoV-2 vital proteins,including the main protease,Nsp12 RNA polymerase and Nsp13 helicase.An integrative virtual screening and molecular dynamics simulations approach has facilitated the identification of potential binding modes and favourable molecular interaction profile of corresponding compounds.Moreover,the identification of structurally important binding site residues in conserved motifs located inside the active site highlights relative importance of ligand binding based on residual energy decomposition analysis.Although the current study lacks experimental validation,the structural information obtained from this computational study has paved way for the design of targeted inhibitors to combat COVID-19 outbreak.
基金funding support from the National Natural Science Foundation of China(Grant Nos.81672467,81702773,81702389,and 81672368)the Major National R&D Project(Grant Nos.2018ZX10723204,2018ZX10302205,and 2018ZX09J18107)the Natural Science Foundation of Beijing(Grant No.7172207)。
文摘Objective:Hepatocellular carcinoma(HCC),the main type of liver cancer,has a high morbidity and mortality,and a poor prognosis.RNA helicase DDX5,which acts as a transcriptional co-regulator,is overexpressed in most malignant tumors and promotes cancer cell growth.Heat shock protein 90(HSP90)is an important molecular chaperone in the conformational maturation and stabilization of numerous proteins involved in cell growth or survival.Methods:DDX5 m RNA and protein expression in surgically resected HCC tissues from 24 Asian patients were detected by quantitative real-time PCR and Western blot,respectively.The interaction of DDX5-HSP90 was determined by molecular docking,immunoprecipitation,and laser scanning confocal microscopy.The autophagy signal was detected by Western blot.The cell functions and signaling pathways of DDX5 were determined in 2 HCC cell lines.Two different murine HCC xenograft models were used to determine the function of DDX5 and the therapeutic effect of an HSP90 inhibitor.Results:HSP90 interacted directly with DDX5 and inhibited DDX5 protein degradation in the AMPK/ULK1-regulated autophagy pathway.The subsequent accumulation of DDX5 protein induced the malignant phenotype of HCC by activating theβ-catenin signaling pathway.The silencing of DDX5 or treatment with HSP90 inhibitor both blocked in vivo tumor growth in a murine HCC xenograft model.High levels of HSP90 and DDX5 protein were associated with poor prognoses.Conclusions:HSP90 interacted with DDX5 protein and subsequently protected DDX5 protein from AMPK/ULK1-regulated autophagic degradation.DDX5 and HSP90 are therefore potential therapeutic targets for HCC.
文摘P68 RNA helicase is a prototypical DEAD box RNA helicase. The protein plays a very important role in early organ development and maturation. Consistent with the function of the protein in transcriptional regulation and pre-mRNA splicing, p68 was found to predominately localize in the cell nucleus. However, recent experiments demon- strate a transient cytoplasmic localization of the protein. We report here that p68 shuttles between the nucleus and the cytoplasm. The nucleocytoplasmic shuttling of p68 is mediated by two nuclear localization signal and two nuclear exporting signal sequence elements. Our experiments reveal that p68 shuttles via a classical RanGTPase-dependent pathway.
基金Supported by Grants from the Ministry of Education of Singapore,Academic Research Fund Tier 1 Grant R-182-000-170-112
文摘The current therapeutic regimen to combat chronic hepatitis C is not optimal due to substantial side effects and the failure of a significant proportion of patients to achieve a sustained virological response. Recently developed direct-acting antivirals targeting hepatitis C virus (HCV) enzymes reportedly increase the virologic response to therapy but may lead to a selection of drug-resistant variants. Besides direct-acting antivirals, another promising class of HCV drugs in development include host targeting agents that are responsible for interfering with the host factors crucial for the viral life cycle. A family of host proteins known as DEAD-box RNA helicases, characterized by nine conserved motifs, is known to play an important role in RNA metabolism. Several members of this family such as DDX3, DDX5 and DDX6 have been shown to play a role in HCV replication and this review will summarize our current knowledge on their interaction with HCV. As chronic hepatitis C is one of the leading causes of hepatocellular carcinoma, the involvement of DEAD-box RNA helicases in the development of HCC will also be highlighted. Continuing research on the interaction of host DEAD-box proteins with HCV and the contribution to viral replication and pathogenesis could be the panacea for the development of novel therapeutics against HCV.
文摘Flaviviruses are positive-sense RNA viruses, and many are important human pathogens. Nonstructural protein 2B and 3 of the flaviviruses(NS2BNS3) form an endoplasmic reticulum(ER) membrane-associated hetero-dimeric complex through the NS2B transmembrane region. The NS2BNS3 complex is multifunctional. The N-terminal region of NS3, and its cofactor NS2B fold into a protease that is responsible for viral polyprotein processing, and the C-terminal domain of NS3 possesses NTPase/RNA helicase activities and is involved in viral RNA replication and virus particle formation. In addition, NS2BNS3 complex has also been shown to modulate viral pathogenesis and the host immune response. Because of the essential functions that the NS2BNS3 complex plays in the flavivirus life cycle, it is an attractive target for antiviral development. This review focuses on the recent biochemical and structural advances of NS2BNS3 and provides a brief update on the current status of drug development targeting this viral protein complex.
基金Project supported by the National Basic Research Program (973) of China (No. 2004CB19604), Distinguished Young Scientist of China (No. 30425038), and the National Natural Science Foundation of China (No. 30330020)
文摘RecQ is a highly conserved helicase necessary for maintaining genome stability in all organisms. Genome comparison showed that a homologue of RecQ in Deinococcus radiodurans designated as DR1289 is a member of RecQ family with unusual domain arrangement: a helicase domain, an RecQ C-terminal domain, and surprisingly three HRDC domain repeats, whose func-tion, however, remains obscure currently. Using an insertion deletion, we discovered that the DRRecQ mutation causes an increase in gamma radiation, hydroxyurea and mitomycine C and UV sensitivity. Using the shuttle plasmid pRADK, we complemented various domains of the D. radiodurans RecQ (DRRecQ) to the mutant in vivo. Results suggested that both the helicase and helicase-and-RNase-D-C-terminal (HRDC) domains are essential for complementing several phenotypes. The complementation and biochemical function of DRRecQ variants with different domains truncated in vitro suggested that both the helicase and three HRDC domains are necessary for RecQ functions in D. radiodurans, while three HRDC domains have a synergistic effect on the whole function. Our finding leads to the hypothesis that the RecF recombination pathway is likely a primary path of double strand break repair in this well-known radioresistant organism.
基金financially supported by grants from the National Natural Science Foundation of China(32072517)the National Key Research and Development Program of China(2018YFD1000105)+2 种基金the Program for Science&Technology Innovation Talents in Universities of Henan Province,China(21HASTIT035)the Program for Innovative Research Team(in Science and Technology)in University of Henan Province,China(21IRTSTHN021)the Science and Technology Planning Project of Luoyang City,China(2101102A)。
文摘Grapevine growing areas are increasingly affected by drought,which has greatly limited global wine production and quality.DEAD-box is one of the largest subfamilies of the RNA helicase family,and its members play key roles in the growth and development of plants and their stress responses.Previous studies have shown the potential of DEAD-box genes in the drought stress responses of Arabidopsis and tomato,rice,and other crop species.However,information about DEAD-box genes in grapevine remains limited.In this report,a total of 40 DEAD-box genes were identified in grapevine and their protein sequence characteristics and gene structures were analyzed.By comparing the expression profiles of VviDEADRHs in response to drought stress in different grapevine varieties,nine candidate genes(VviDEADRH10c,-13,-22,-25a,-25b,-33,-34,-36,and-39)were screened based on expression profiling data.Combined with qRTPCR results,Vvi DEADRH25a was selected for functional verification.Heterologous overexpression of Vvi DEADRH25a in Arabidopsis showed the transgenic plants were more sensitive to drought stress than the control.Both electrolyte permeability and malondialdehyde content were significantly increased in transgenic plants,whereas the chlorophyll content and superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),and ascorbate peroxidase(APX)enzyme activities were significantly decreased.Furthermore,VviDEADRH25a-overexpressing plants showed down-regulated expression levels of several drought stress-related marker genes,namely At COR15a,At RD29A,At ERD15,and At P5CS1,which indicated that they participated in the drought stress response.In summary,this study provides new insights into the structure,evolution,and participation of DEAD-box RNA helicase genes in the response to drought stress in grapevines.
基金Supported by The National Center for Advancing Translational Sciences of the National Institutes of Health under award numbers ULl TR000454 previously awarded to Dr.Colbert and Dr.Fisher and TLlT R000456 to Dr.ColbertPancreatic Cancer Action Network(Pan-CAN)&sol American Association for Cancer Research(AACR)award 16982+1 种基金Department of Defense(DOD)/Peer Reviewed Cancer Research Program(PRCRP)award CA110535Georgia Cancer Coalition award 11072,all to Dr.Yu
文摘Pancreatic cancer is one of the deadliest cancers with a very poor prognosis. Recently, there has been a significant increase in research directed towards identifying potential biomarkers that can be used to diagnose and provide prognostic information for pancreatic cancer. These markers can be used clinically to optimize and personalize therapy for individual patients. In this review, we focused on 3 biomarkers involved in the DNA damage response pathway and the necroptosis pathway: Chromodomainhelicase-DNA binding protein 5, chromodomain-helicaseDNA binding protein 7, and mixed lineage kinase domain-like protein. The aim of this article is to review present literature provided for these biomarkers and current studies in which their effectiveness as prognostic biomarkers are analyzed in order to determine their future use as biomarkers in clinical medicine. Based on the data presented, these biomarkers warrant further investigation,and should be validated in future studies.
基金The project supported by grants from the Academic Research Fund Tier 1(R-184-000-228-112)the Cancer Science Institute of Singapore,Experimental Therapeutics I Program(grant R-713-001-011-271)
文摘OBJECTIVE To evaluate if RNA helicase DDX20,highly expressed in triple negative breast cancer(TNBC)cells,could serve as a surrogate marker for simvastatin treatment response.METHODS We first assessed correlation between 17 mevalonate pathway-related genes and expression of DDX20 in a cohort of 1325 breast cancer tumors.TNBC cells,MDA-MB-231,were then treated with simvastatin and mevalonate pathway intermediates to assess the alteration in DDX20 expression.In the mouse model,MDA-MB-231 cells were injected to tail veins of mice,groups of 8mice each were injected intraperioneally with vehicle or simvastatin 25mg·kg-1 3times a week for 6weeks.The number of metastatic colonies formed was quantified and immunohistochemical(IHC)staining of DDX20 was carried out in the lung tissues.RESULTS Among the 17 genes evaluated,positive correlation with DDX20 expression was observed in eight of them,with HMGCR having the highest correlation.Our in vitro experiments show exposure of breast cancer cells to simvastatin lead to a Rho-dependent decrease in gene expression of DDX20,leading to decreased tumor proliferation in a mevalonate pathway-dependent manner.Conversely,ectopic overexpression of DDX20 significantly abrogated the anti-metastatic activity of simvastatin.A similar observation is seen in the mouse model,where simvastatin-injected mice show significantly fewer visible lung metastases compared to placebo-fed mice.IHC staining on these lung tissues showed decreased DDX20 expression in simvastatin-injected group,corroborating our observations in vitro.CONCLUSION DDX20 is a potential surrogate marker for simvastatin treatment response in breast cancer and a long term implication of our findings is the possibility of an effective combinatorial therapeutic intervention using statins(to suppress DDX20 gene expression)and a suitable firstline agent″for the kill″of invasive breast cancer.
基金supported by the National Natural Science Foundation of China(Grant Nos.11674383,11474346,and 11274374)the National Basic Research Program of China(Grant No.2013CB837200)the National Key Research and Development Program of China(Grant No.2016YFA0301500)
文摘RecQ5β is an essential DNA helicase in humans, playing important roles in DNA replication, repair, recombination and transcription. The unwinding activity and substrate specificity of RecQ5β is still elusive. Here, we used stopped-flow kinetic method to measure the unwinding and dissociation kinetics of RecQ5β with several kinds of DNA substrates, and found that RecQ5β could well unwind ss/ds DNA, forked DNA and Holiday junction, but was compromised in unwinding blunt DNA and G-quadruplex. Rec5β has the preferred unwinding specificity for certain DNA substrates containing the junction point, which may improve the binding affinity and unwinding activity of RecQ5β. Moreover, from a comparison with the truncated RecQ5β~(1-467), we discovered that the C-terminal domain might strongly influence the unwinding activity and binding affinity of RecQ5β. These results may shed light on the physiological functions and working mechanisms of RecQ5β helicase.
文摘Hepatitis C virus(HCV)helicase is a molecular motor that splits nucleic acid duplex structures during viral replication,therefore representing a promising target for antiviral treatment.Hence,a detailed understanding of the mechanism by which it operates would facilitate the development of efficient drug-assisted therapies aiming to inhibit helicase activity.Despite extensive investigations performed in the past,a thorough understanding of the activity of this important protein was lacking since the underlying internal conformational motions could not be resolved.Here we review investigations that have been previously performed by us for HCV helicase.Using methods of structure-based computational modelling it became possible to follow entire operation cycles of this motor protein in structurally resolved simulations and uncover the mechanism by which it moves along the nucleic acid and accomplishes strand separation.We also discuss observations from that study in the light of recent experimental studies that confirm our findings.
文摘猪肺炎支原体的持续性感染问题频发,同源重组介导的抗原变异扮演重要角色。解螺旋酶RuvA调节霍利迪连接体变构是参与同源重组的关键步骤。鉴于此,本研究旨在原核表达猪肺炎支原体解螺旋酶RuvA重组蛋白,鉴定其DNA结合活性并制备多克隆抗体。试验通过分子克隆构建原核表达质粒pET21a-RuvA,经诱导表达和纯化获得RuvA M hp重组蛋白;免疫家兔制备抗RuvA M hp多克隆抗体,再利用间接ELISA和Western blot试验进行效价测定和特异性验证;利用凝胶迁移试验结合表面等离子共振技术分析RuvA M hp的DNA结合活性;利用凝胶迁移试验结合Western blot试验鉴定RuvA M hp的寡聚特性。结果显示:原核表达的RuvA M hp重组蛋白约为26 ku;制备的抗RuvA M hp多克隆抗体效价为1∶256000,且具有良好的特异性;RuvA M hp具有较强的DNA结合活性,对霍利迪连接体的亲和力高达624.4 pmol·L^(-1)(K D),并且主要以八聚体形式与其形成稳定复合物。通过RuvA M hp的原核表达、多克隆抗体制备及活性鉴定,为后续探索RuvA调解同源重组介导猪肺炎支原体抗原变异的分子机制奠定了基础。