Human immunodeficiency virus type 1 （HIV-1） Vpr induces cell death in mammalian and fssion yeast cells, suggesting that Vpr may affect a conserved cellular process. It is unclear, however, whether Vpr-induced yeast ...Human immunodeficiency virus type 1 （HIV-1） Vpr induces cell death in mammalian and fssion yeast cells, suggesting that Vpr may affect a conserved cellular process. It is unclear, however, whether Vpr-induced yeast cell death mimics Vpr-mediated apoptosis in mammalian cells. We have recently identified a number of Vpr suppressors that not only suppress Vpr-induced cell death in fission yeast, but also block Vpr-induced apoptosis in mammalian cells. These findings suggest that Vpr-induced cell death in yeast may resemble some of the apoptotic processes of mammalian cells. The goal of this study was to develop and validate a fission yeast model system for future studies of apoptosis. Similar to Vpr-induced apoptosis in mammalian cells, we show here that Vpr in fission yeast promotes phosphatidylserine externalization and induces hyperpolarization of mitochondria, leading to changes of mitochondrial membrane potential. Moreover, Vpr triggers production of reactive oxygen species （ROS）, indicating that the apoptotic-like cell death might be mediated by ROS. Interestingly, Vpr induces unique morphologic changes in mitochondria that may provide a simple marker for measuring the apoptotic-like process in fission yeast. To verify this possibility, we tested two Vpr suppressors （EF2 and Hspl6） that suppress Vpr-induced apoptosis in mammalian cells in addition to a newly identified Vpr suppressor （Skpl）. All three proteins abolished cell death mediated by Vpr and restored normal mitochondrial morphology in the yeast cells. In conclusion, Vpr-induced cell death in fission yeast resembles the mammalian apoptotic process. Fission yeast may thus potentially be used as a simple model organism for the future study of the apoptotic-like process induced by Vpr and other proapoptotic agents.展开更多
Gaining a full understanding of the mechanisms of action of natural products as therapeutic agents includes observing the effects of natural products on cellular morphology,because abnormal cellular morphology is an i...Gaining a full understanding of the mechanisms of action of natural products as therapeutic agents includes observing the effects of natural products on cellular morphology,because abnormal cellular morphology is an important aspect of cellular transformations that occur as part of disease states.In this study a set of natural products was examined in search of small molecules that influence the cylindrical morphology of fission yeast Schizosaccharomyces pombe.Imaging flow cytometry of large populations of S.pombe exposed to natural products captured cell images and revealed changes in mean length and aspect ratio of cells.Several natural products were found to alter S.pombe’s morphology relative to control,in terms of elongating cells,shrinking them,or making them more round.These results may facilitate future investigations into methods by which cells establish and maintain specific shapes.展开更多
Objective: To analyze potential activation of oxidative stress tolerance systems by SAB E-41 bacterial extract in promoting the life span of yeast Schizosaccharomyces pombe. Methods: In vitro analysis was done to asse...Objective: To analyze potential activation of oxidative stress tolerance systems by SAB E-41 bacterial extract in promoting the life span of yeast Schizosaccharomyces pombe. Methods: In vitro analysis was done to assess antioxidant activity of SAB E-41 bacterial extract. Antiaging property of the particular extract was then assayed through spot test and chronological life span assays. Furthermore, sty1 mitogen-activated protein kinase, pap1 transcriptional factor of oxidative stress response and its downstream genes, ctt1 were evaluated via real time PCR. The protein level of ctt1 was then observed via Western Blot analysis. In addition, accumulation of reactive oxygen species and mitochondrial activity were conducted to understand the effect of SAB E-41 upon oxidative stress response systems in vivo. Results: The IC50 values of corresponding extract for antioxidant(DPPH; ABTS) and antiglycation were 402.40, 358.13 and 683.55 μg/mL, respectively. In addition, SAB E-41 extract(750 μg/mL) exhibited antiaging properties, which could be attributed to significant up-regulation of oxidative stress response genes, sty1, pap1 and ctt1. Interestingly, SAB E-41 extract could enhance stress tolerance phenotype of Schizosaccharomyces pombe against H2 O2-induced oxidative stress. These results were supported by increasing mitochondrial activity and reactive oxygen species intracellular levels. Conclusions: SAB E-41 extract could promote yeast life span likely via up-regulation of oxidative stress responses in yeast. Our results suggest that adaptive response via up-regulation of oxidative stress transcriptional factors, and its downstream gene, ctt1, as well as mitochondrial activity contributes in combating oxidative stress thus promoting yeast life span.展开更多
A new copper(Ⅱ) complex of CuLCl_2, where L = N^1-(1-pyrazin-2-yl-ethylidene)-ethane-1,2-diamine, a tridentate Schiff base derived from 2-acetylpyrazine has been prepared. The complex has been characterized by FT-IR,...A new copper(Ⅱ) complex of CuLCl_2, where L = N^1-(1-pyrazin-2-yl-ethylidene)-ethane-1,2-diamine, a tridentate Schiff base derived from 2-acetylpyrazine has been prepared. The complex has been characterized by FT-IR, elemental analysis and single-crystal X-ray diffraction studies. Structural studies reveal that CuLCl_2 is a mononuclear copper(Ⅱ) complex with distorted square pyramidal geometry. Antifungal activity of CuLCl_2 was investigated by use of microcalorimetric measurement system and evaluated against S. pombe. It has high antifungal activity with IC_(50) = 213 μg/mL.展开更多
[ Objective] This study aimed to investigate the effect in cell cycle caused by overexpression of SpTrz2p in Schizosaccharomyces pombe. [ Method] The trz2 ~ gene from S. pombe was cloned into pREPgx plasmid to constru...[ Objective] This study aimed to investigate the effect in cell cycle caused by overexpression of SpTrz2p in Schizosaccharomyces pombe. [ Method] The trz2 ~ gene from S. pombe was cloned into pREPgx plasmid to construct an overexpression vector of SpTrz2p, which was then transformed into wild-type S. pombe ceils. The cell cycle was determined with flow cytometry. [ Result ] Overexpression of SpTrz2p in yeast caused changes in cell morphology and cell cycle. The majority of the cells were arrested at G1 phase, indicating that overexpression of SpTrz2p indeed affected the cell cycle. [ Conclusion] This study suggested that overexpression of SpTrz2p is lethal to the cells by affecting the cell cycle.展开更多
The roles of nucleotide excision repair (NER) proteins in removing UV-induced lesions are well defined. There are two distinct NER pathways: global genome NER (GG-NER) and transcription-coupled NER. In human GG-NER, t...The roles of nucleotide excision repair (NER) proteins in removing UV-induced lesions are well defined. There are two distinct NER pathways: global genome NER (GG-NER) and transcription-coupled NER. In human GG-NER, two heteromeric protein complexes, DDB1-DDB2 and XPC-RAD23, are responsible for initial lesion recognition. Here, we examined the genetic interactions between GG-NER and base excision repair (BER) genes during abasic (AP) site repair of Schizosaccharomyces pombe. Mutants of rhp7 (rhp7-rhp16 are functional homologs of DDB1-DDB2) and rhp41 (XPC homolog) were moderately sensitive to methyl methanesulfonate and slightly to sodium bisulfite. Nth1p most actively cleaves the AP site in S. pombe. Deletion of rhp7 or rhp41 from nth1Δ cells greatly increased their sensitivity to alkylation and deamination, indicating that Rhp7p and Rhp41p are involved in repair of the AP sites generated by the action of DNA glycosylase. Induction of rhp7 and rhp16 genes by different types of DNA damage supports the ability of GG-NER to remove non-bulky lesions. Therefore, GG-NER activity not only targets bulky DNA helix-distorting lesions, but can also efficiently remove AP sites synergistically with BER.展开更多
Interaction between the HIV-1 Vif protein and the cellular host APOBEC3G protein is a promising target for inhibition of HIV-1 replication. Considering that human cells are a very complicated environment for the study...Interaction between the HIV-1 Vif protein and the cellular host APOBEC3G protein is a promising target for inhibition of HIV-1 replication. Considering that human cells are a very complicated environment for the study of protein interactions, the goal of this study was to check whether fission yeast could be used as a model cell for studying the Vif-APOBEC3G interaction. Vif and APOBEC3G were expressed in fusion with GFP protein in the S. pombe SP223 strain. Subcellular localizations of Vif and APOBEC3G were observed with fluorescent microscopy. Codon optimization was used to over express the Vif protein in S. pombe cells. The degradation of APOBEC3G mediated by Vif was tested through expressing Vif and GFP-APOBEC3G proteins in the same cell. Western Blot analysis was used to measure the corresponding protein levels under different experimental conditions. The results showed that the Vif protein was predominantly localized in the nucleus of S. pombe cells, APOBEC3G was localized in the cytoplasm and concentrated at punctate bodies that were often in close proximity to the nucleus but were not necessarily restricted from other regions in the cytoplasm. Vif protein expression levels were increased significantly by using codon optimization and APOBEC3G was degraded when Vif was over-expressed in the same S. pombe cells. These results indicate that fission yeast is a good model for studying the interaction between the Vif and APOBEC3G proteins.展开更多
The metabolic enzyme CTP synthase(CTPS) is able to compartmentalize into filaments,termed cytoophidia,in a variety of organisms including bacteria,budding yeast,fission yeast,fruit flies and mammals.A previous study i...The metabolic enzyme CTP synthase(CTPS) is able to compartmentalize into filaments,termed cytoophidia,in a variety of organisms including bacteria,budding yeast,fission yeast,fruit flies and mammals.A previous study in budding yeast shows that the filament-forming process of CTPS is not sensitive to temperature shift.Here we study CTPS filamentation in the fission yeast Schizosaccharomyces pombe.To our surprise,we find that both the length and the occurrence of cytoophidia in S.pombe decrease upon cold shock or heat shock.The temperature-dependent changes of cytoophidia are fast and reversible.Taking advantage of yeast genetics,we demonstrate that heat-shock proteins are required for cytoophidium assembly in S.pombe.Temperature sensitivity of cytoophidia makes S.pombe an attractive model system for future investigations of this novel membraneless organelle.展开更多
Progression of cells from G2 phase of the cell cycle to mitosis is a tightly regulated cellular process that requires activation of the Cdc2 kinase, which determines onset of mitosis in all eukaryotic cells. In both h...Progression of cells from G2 phase of the cell cycle to mitosis is a tightly regulated cellular process that requires activation of the Cdc2 kinase, which determines onset of mitosis in all eukaryotic cells. In both human and fission yeast (Schizosaccharomyces pombe) cells, the activity of Cdc2 is regulated in part by the phosphorylation status of tyrosine 15 (Tyr15) on Cdc2, which is phosphorylated by Wee1 kinase during late G2 and is rapidly dephosphorylated by the Cdc25 tyrosine phosphatase to trigger entry into mitosis. These Cdc2 regulators are the downstream targets of two well- characterized G2/M checkpoint pathways which prevent cells from entering mitosis when cellular DNA is damaged or when DNA replication is inhibited. Increasing evidence suggests that Cdc2 is also commonly targeted by viral proteins, which modulate host cell cycle machinery to benefit viral survival or replication. In this review, we describe the effect of viral protein R (Vpr) encoded by human immunodeficiency virus type 1 (HIV-1) on cell cycle G2/M regulation. Based on our current knowledge about this viral effect, we hypothesize that Vpr induces cell cycle G2 arrest through a mechanism that is to some extent different from the classic G2/M checkpoints. One the unique features distinguishing Vpr-induced G2 arrest from the classic checkpoints is the role of phosphatase 2A (PP2A) in Vpr-induced G2 arrest. Interestingly, PP2A is targeted by a number of other viral proteins including SV40 small T antigen, polyomavirus T antigen, HTLV Tax and adenovirus E4orf4. Thus an in-depth understanding of the molecular mechanisms underlying Vpr-induced G2 arrest will provide additional insights into the basic biology of cell cycle G2/M regulation and into the biological significance of this effect during host-pathogen interactions.展开更多
By using the method of reverse transcription at different dNTP concentrations, a novel methylated nucleoside, Am64, has been identified from Schizosaccharomyces pombe U6 snRNA, and a higher ordered structure repressin...By using the method of reverse transcription at different dNTP concentrations, a novel methylated nucleoside, Am64, has been identified from Schizosaccharomyces pombe U6 snRNA, and a higher ordered structure repressing the passage of reverse transcriptase at the 5’ end of U6 snRNA has been demonstrated.展开更多
This study was designed to identify and investigate bioactive natural product compounds that alter the cellular shape of the fission yeast Schizosaccharomyces pombe and induce a“rounded”or“small”cellular morpholog...This study was designed to identify and investigate bioactive natural product compounds that alter the cellular shape of the fission yeast Schizosaccharomyces pombe and induce a“rounded”or“small”cellular morphological phenotype.Bioassays using a range of antifungal agents against a multidrug-sensitive fission yeast strain,SAK950 showed that many induced a“rounded”phenotype.We then investigated whether 46 of the actinomycete strains identified in our previous study as inducing a similar phenotype produced antifungal agents of similar classes.We show that five of the strains produced streptothricin and that 26 strains produced polyenes,including fungichromin,filipin and candicidin,the last of which was produced by 24 strains.A taxonomic study of the strains indicated that the majority of the candicidin only producers were Streptomyces hydrogenans and S.albidoflavus whilst those that additionally produced streptothricin were related to S.enissocaesilis.A follow-up study to investigate the natural products made by related strains indicated that they followed a similar pattern.The identification of several compounds from the actinomycete strains similar to the antifungal agents initially tested confirm the validity of an approach using the S.pombe morphological phenotype and actinomycete taxonomy as a predictive tool for natural product identification.展开更多
In this paper, a novel bismuthoxide Schiff-base complex [Bi9O8（vanen）3（NO3）2（CH3OH）2（H2O）·3NO3· 5.5H2O]（abbreviated as Bivanen） was synthesized with Salen-like ligand Hzvanen[Hzvanen=N,N＇-ethylene...In this paper, a novel bismuthoxide Schiff-base complex [Bi9O8（vanen）3（NO3）2（CH3OH）2（H2O）·3NO3· 5.5H2O]（abbreviated as Bivanen） was synthesized with Salen-like ligand Hzvanen[Hzvanen=N,N＇-ethylene bis（3-methoxysalicylideneimine）] and bismuth（III） nitrate. Its structure was characterized by IR spectra, NMR spectra and X-ray diffraction. In particular, the biology activities of the ligand and the complex against Schizosaecharomyees pombe（S, pombe） were studied using biological mierocalorimetry. The metabolic thermogenic curves of S. pombe were measured at 32.00 ℃. Then, some quantitative thermokinetic parameters of growth metabolism of S. pombe including the rate constant（k）, inhibition ratio（I） and half inhibition concentration（IC50） were calculated. Experimental results showed that the k values of S. pombe decreased while I values of S. pombe increased with the increase of concentrations of the ligand and the complex. The IC50 of the ligand and the complex were found to be 0.067 and 0.037 mmol/L, respectively.展开更多
文摘Human immunodeficiency virus type 1 （HIV-1） Vpr induces cell death in mammalian and fssion yeast cells, suggesting that Vpr may affect a conserved cellular process. It is unclear, however, whether Vpr-induced yeast cell death mimics Vpr-mediated apoptosis in mammalian cells. We have recently identified a number of Vpr suppressors that not only suppress Vpr-induced cell death in fission yeast, but also block Vpr-induced apoptosis in mammalian cells. These findings suggest that Vpr-induced cell death in yeast may resemble some of the apoptotic processes of mammalian cells. The goal of this study was to develop and validate a fission yeast model system for future studies of apoptosis. Similar to Vpr-induced apoptosis in mammalian cells, we show here that Vpr in fission yeast promotes phosphatidylserine externalization and induces hyperpolarization of mitochondria, leading to changes of mitochondrial membrane potential. Moreover, Vpr triggers production of reactive oxygen species （ROS）, indicating that the apoptotic-like cell death might be mediated by ROS. Interestingly, Vpr induces unique morphologic changes in mitochondria that may provide a simple marker for measuring the apoptotic-like process in fission yeast. To verify this possibility, we tested two Vpr suppressors （EF2 and Hspl6） that suppress Vpr-induced apoptosis in mammalian cells in addition to a newly identified Vpr suppressor （Skpl）. All three proteins abolished cell death mediated by Vpr and restored normal mitochondrial morphology in the yeast cells. In conclusion, Vpr-induced cell death in fission yeast resembles the mammalian apoptotic process. Fission yeast may thus potentially be used as a simple model organism for the future study of the apoptotic-like process induced by Vpr and other proapoptotic agents.
基金financial support from the University of North Florida.
文摘Gaining a full understanding of the mechanisms of action of natural products as therapeutic agents includes observing the effects of natural products on cellular morphology,because abnormal cellular morphology is an important aspect of cellular transformations that occur as part of disease states.In this study a set of natural products was examined in search of small molecules that influence the cylindrical morphology of fission yeast Schizosaccharomyces pombe.Imaging flow cytometry of large populations of S.pombe exposed to natural products captured cell images and revealed changes in mean length and aspect ratio of cells.Several natural products were found to alter S.pombe’s morphology relative to control,in terms of elongating cells,shrinking them,or making them more round.These results may facilitate future investigations into methods by which cells establish and maintain specific shapes.
基金supported by Master program of Education Leading to Doctoral Degree for Excellent Graduate program 2017 from the Ministry of Research,Technology,and Higher Education of the Republic of Indonesia(No.136/SP2H/LT/DRPM/IV/2017)
文摘Objective: To analyze potential activation of oxidative stress tolerance systems by SAB E-41 bacterial extract in promoting the life span of yeast Schizosaccharomyces pombe. Methods: In vitro analysis was done to assess antioxidant activity of SAB E-41 bacterial extract. Antiaging property of the particular extract was then assayed through spot test and chronological life span assays. Furthermore, sty1 mitogen-activated protein kinase, pap1 transcriptional factor of oxidative stress response and its downstream genes, ctt1 were evaluated via real time PCR. The protein level of ctt1 was then observed via Western Blot analysis. In addition, accumulation of reactive oxygen species and mitochondrial activity were conducted to understand the effect of SAB E-41 upon oxidative stress response systems in vivo. Results: The IC50 values of corresponding extract for antioxidant(DPPH; ABTS) and antiglycation were 402.40, 358.13 and 683.55 μg/mL, respectively. In addition, SAB E-41 extract(750 μg/mL) exhibited antiaging properties, which could be attributed to significant up-regulation of oxidative stress response genes, sty1, pap1 and ctt1. Interestingly, SAB E-41 extract could enhance stress tolerance phenotype of Schizosaccharomyces pombe against H2 O2-induced oxidative stress. These results were supported by increasing mitochondrial activity and reactive oxygen species intracellular levels. Conclusions: SAB E-41 extract could promote yeast life span likely via up-regulation of oxidative stress responses in yeast. Our results suggest that adaptive response via up-regulation of oxidative stress transcriptional factors, and its downstream gene, ctt1, as well as mitochondrial activity contributes in combating oxidative stress thus promoting yeast life span.
基金supported by the National Natural Science Foundation of China(No.41701349)
文摘A new copper(Ⅱ) complex of CuLCl_2, where L = N^1-(1-pyrazin-2-yl-ethylidene)-ethane-1,2-diamine, a tridentate Schiff base derived from 2-acetylpyrazine has been prepared. The complex has been characterized by FT-IR, elemental analysis and single-crystal X-ray diffraction studies. Structural studies reveal that CuLCl_2 is a mononuclear copper(Ⅱ) complex with distorted square pyramidal geometry. Antifungal activity of CuLCl_2 was investigated by use of microcalorimetric measurement system and evaluated against S. pombe. It has high antifungal activity with IC_(50) = 213 μg/mL.
基金Supported by the National Natural Science Foundation of China(30771178)
文摘[ Objective] This study aimed to investigate the effect in cell cycle caused by overexpression of SpTrz2p in Schizosaccharomyces pombe. [ Method] The trz2 ~ gene from S. pombe was cloned into pREPgx plasmid to construct an overexpression vector of SpTrz2p, which was then transformed into wild-type S. pombe ceils. The cell cycle was determined with flow cytometry. [ Result ] Overexpression of SpTrz2p in yeast caused changes in cell morphology and cell cycle. The majority of the cells were arrested at G1 phase, indicating that overexpression of SpTrz2p indeed affected the cell cycle. [ Conclusion] This study suggested that overexpression of SpTrz2p is lethal to the cells by affecting the cell cycle.
文摘The roles of nucleotide excision repair (NER) proteins in removing UV-induced lesions are well defined. There are two distinct NER pathways: global genome NER (GG-NER) and transcription-coupled NER. In human GG-NER, two heteromeric protein complexes, DDB1-DDB2 and XPC-RAD23, are responsible for initial lesion recognition. Here, we examined the genetic interactions between GG-NER and base excision repair (BER) genes during abasic (AP) site repair of Schizosaccharomyces pombe. Mutants of rhp7 (rhp7-rhp16 are functional homologs of DDB1-DDB2) and rhp41 (XPC homolog) were moderately sensitive to methyl methanesulfonate and slightly to sodium bisulfite. Nth1p most actively cleaves the AP site in S. pombe. Deletion of rhp7 or rhp41 from nth1Δ cells greatly increased their sensitivity to alkylation and deamination, indicating that Rhp7p and Rhp41p are involved in repair of the AP sites generated by the action of DNA glycosylase. Induction of rhp7 and rhp16 genes by different types of DNA damage supports the ability of GG-NER to remove non-bulky lesions. Therefore, GG-NER activity not only targets bulky DNA helix-distorting lesions, but can also efficiently remove AP sites synergistically with BER.
基金National Grand Fundamental Research 973 Program of China (2006CB504206).
文摘Interaction between the HIV-1 Vif protein and the cellular host APOBEC3G protein is a promising target for inhibition of HIV-1 replication. Considering that human cells are a very complicated environment for the study of protein interactions, the goal of this study was to check whether fission yeast could be used as a model cell for studying the Vif-APOBEC3G interaction. Vif and APOBEC3G were expressed in fusion with GFP protein in the S. pombe SP223 strain. Subcellular localizations of Vif and APOBEC3G were observed with fluorescent microscopy. Codon optimization was used to over express the Vif protein in S. pombe cells. The degradation of APOBEC3G mediated by Vif was tested through expressing Vif and GFP-APOBEC3G proteins in the same cell. Western Blot analysis was used to measure the corresponding protein levels under different experimental conditions. The results showed that the Vif protein was predominantly localized in the nucleus of S. pombe cells, APOBEC3G was localized in the cytoplasm and concentrated at punctate bodies that were often in close proximity to the nucleus but were not necessarily restricted from other regions in the cytoplasm. Vif protein expression levels were increased significantly by using codon optimization and APOBEC3G was degraded when Vif was over-expressed in the same S. pombe cells. These results indicate that fission yeast is a good model for studying the interaction between the Vif and APOBEC3G proteins.
基金supported by the UK Medical Research Council(Grant No.MC_UU_12021/3 and MC_U137788471)University of OxfordShanghaiTech University
文摘The metabolic enzyme CTP synthase(CTPS) is able to compartmentalize into filaments,termed cytoophidia,in a variety of organisms including bacteria,budding yeast,fission yeast,fruit flies and mammals.A previous study in budding yeast shows that the filament-forming process of CTPS is not sensitive to temperature shift.Here we study CTPS filamentation in the fission yeast Schizosaccharomyces pombe.To our surprise,we find that both the length and the occurrence of cytoophidia in S.pombe decrease upon cold shock or heat shock.The temperature-dependent changes of cytoophidia are fast and reversible.Taking advantage of yeast genetics,we demonstrate that heat-shock proteins are required for cytoophidium assembly in S.pombe.Temperature sensitivity of cytoophidia makes S.pombe an attractive model system for future investigations of this novel membraneless organelle.
基金supported in part by grants from the National Institute of Health GM89630 and AI63080an endowed Research Scholar Chair by the Medical Research Institute Councilby an internal grant of the University of Maryland Medical Center(RYZ).
文摘Progression of cells from G2 phase of the cell cycle to mitosis is a tightly regulated cellular process that requires activation of the Cdc2 kinase, which determines onset of mitosis in all eukaryotic cells. In both human and fission yeast (Schizosaccharomyces pombe) cells, the activity of Cdc2 is regulated in part by the phosphorylation status of tyrosine 15 (Tyr15) on Cdc2, which is phosphorylated by Wee1 kinase during late G2 and is rapidly dephosphorylated by the Cdc25 tyrosine phosphatase to trigger entry into mitosis. These Cdc2 regulators are the downstream targets of two well- characterized G2/M checkpoint pathways which prevent cells from entering mitosis when cellular DNA is damaged or when DNA replication is inhibited. Increasing evidence suggests that Cdc2 is also commonly targeted by viral proteins, which modulate host cell cycle machinery to benefit viral survival or replication. In this review, we describe the effect of viral protein R (Vpr) encoded by human immunodeficiency virus type 1 (HIV-1) on cell cycle G2/M regulation. Based on our current knowledge about this viral effect, we hypothesize that Vpr induces cell cycle G2 arrest through a mechanism that is to some extent different from the classic G2/M checkpoints. One the unique features distinguishing Vpr-induced G2 arrest from the classic checkpoints is the role of phosphatase 2A (PP2A) in Vpr-induced G2 arrest. Interestingly, PP2A is targeted by a number of other viral proteins including SV40 small T antigen, polyomavirus T antigen, HTLV Tax and adenovirus E4orf4. Thus an in-depth understanding of the molecular mechanisms underlying Vpr-induced G2 arrest will provide additional insights into the basic biology of cell cycle G2/M regulation and into the biological significance of this effect during host-pathogen interactions.
文摘By using the method of reverse transcription at different dNTP concentrations, a novel methylated nucleoside, Am64, has been identified from Schizosaccharomyces pombe U6 snRNA, and a higher ordered structure repressing the passage of reverse transcriptase at the 5’ end of U6 snRNA has been demonstrated.
基金the Francis Crick Institute which receives its core funding from Cancer Research UK(FC001121)the UK Medical Research Council(FC001121)+2 种基金the Wellcome Trust(FC001121)In addition,this work was supported by a Wellcome Trust grant to P.N.(Grant Number 093917)Demuris Ltd.
文摘This study was designed to identify and investigate bioactive natural product compounds that alter the cellular shape of the fission yeast Schizosaccharomyces pombe and induce a“rounded”or“small”cellular morphological phenotype.Bioassays using a range of antifungal agents against a multidrug-sensitive fission yeast strain,SAK950 showed that many induced a“rounded”phenotype.We then investigated whether 46 of the actinomycete strains identified in our previous study as inducing a similar phenotype produced antifungal agents of similar classes.We show that five of the strains produced streptothricin and that 26 strains produced polyenes,including fungichromin,filipin and candicidin,the last of which was produced by 24 strains.A taxonomic study of the strains indicated that the majority of the candicidin only producers were Streptomyces hydrogenans and S.albidoflavus whilst those that additionally produced streptothricin were related to S.enissocaesilis.A follow-up study to investigate the natural products made by related strains indicated that they followed a similar pattern.The identification of several compounds from the actinomycete strains similar to the antifungal agents initially tested confirm the validity of an approach using the S.pombe morphological phenotype and actinomycete taxonomy as a predictive tool for natural product identification.
基金Supported by the National Natural Science Foundation of China（Nos.21273190, 20973145） and the Science and Technology Plan Projects of Hunan Province, China（Nos.2014F J3011, 2013F J3033, 2014TT2026）.
文摘In this paper, a novel bismuthoxide Schiff-base complex [Bi9O8（vanen）3（NO3）2（CH3OH）2（H2O）·3NO3· 5.5H2O]（abbreviated as Bivanen） was synthesized with Salen-like ligand Hzvanen[Hzvanen=N,N＇-ethylene bis（3-methoxysalicylideneimine）] and bismuth（III） nitrate. Its structure was characterized by IR spectra, NMR spectra and X-ray diffraction. In particular, the biology activities of the ligand and the complex against Schizosaecharomyees pombe（S, pombe） were studied using biological mierocalorimetry. The metabolic thermogenic curves of S. pombe were measured at 32.00 ℃. Then, some quantitative thermokinetic parameters of growth metabolism of S. pombe including the rate constant（k）, inhibition ratio（I） and half inhibition concentration（IC50） were calculated. Experimental results showed that the k values of S. pombe decreased while I values of S. pombe increased with the increase of concentrations of the ligand and the complex. The IC50 of the ligand and the complex were found to be 0.067 and 0.037 mmol/L, respectively.
