Membrane fusion is the last step in trafficking pathways during which membrane vesicles fuse with target organelles to deliver cargos. It is a central cellular reaction that plays important roles in signal transductio...Membrane fusion is the last step in trafficking pathways during which membrane vesicles fuse with target organelles to deliver cargos. It is a central cellular reaction that plays important roles in signal transduction, protein sorting and subcellular compartmentation. Recent progress in understanding the roles of ion transporters in vacuole fusion in yeast is summarized in this article. It is becoming increasingly evident that the vacuolar proton pump V-ATPase and vacuolar Na＋/H＋ antiporter ScNhxlp are key components of the vacuole fusion machinery in yeast. Yeast ScNhxlp regulates vacuole fusion by controlling the luminal pH. V-ATPases serve a dual role in vacuolar integrity in which they regulate both vacuole fusion and fission reactions in yeast. Fission defects are epistatic to fusion defects. Vacuole fission depends on the proton translocation activity of the V-ATPase; by contrast, the fusion reaction does not need the transport activity but requires the physical presence of the proton pump. V0, the membrane-integral sector of the V-ATPase, forms trans-complexes between the opposing vacuoles in the terminal phase of vacuole fusion where the V0 trans-complexes build a continuous proteolipid channel at the fusion site to mediate the bilayer fusion.展开更多
All Chinese born in the 1960's know the famous movie script "the function of a horse tail". Indeed, there is another famous "horse tail" in the field of basic biology, the premeiotic nucleus in...All Chinese born in the 1960's know the famous movie script "the function of a horse tail". Indeed, there is another famous "horse tail" in the field of basic biology, the premeiotic nucleus in the fission yeast Schizosaccharomyces pombe. It is not only because of its characteristic shape which looks like a horse tail, but also its dramatic oscillatory movement called "the horsetail movement". In the horsetail nucleus, all of the ends of chromosomes, the telomeres, are tightly clustering under spindle pole body (a centrosome equivalent in yeasts). Actually, this horsetail chromosome arrangement is an extreme form of so called "bouquet arrangement", a polarized chromosome arrangement with all the telomeres clustered in a confined area on the nuclear envelope. Bouquet arrangement is widely conserved meiotic prophase chromosomal phenomenon among eukaryotes. From study of the horsetail nucleus in fission yeast, many progresses have been made in the field of meiosis.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 GbKTN1 gene was isolated from 10 DPA fiber cells of Gossypium barbadense using 5′RACE/3′RACE.Full-length cDNA of this gene is 2006 bp, including a 113 bp of 5′untranslated region, a 1563 bp of an open reading f...The GbKTN1 gene was isolated from 10 DPA fiber cells of Gossypium barbadense using 5′RACE/3′RACE.Full-length cDNA of this gene is 2006 bp, including a 113 bp of 5′untranslated region, a 1563 bp of an open reading frame(ORF), and a 327 bp of 3′untranslated region (excluding the stop codon TAA). The ORF of GbKTN1 encodes a 521-amino acid protein with a predicted size of 55 kD. Near C-terminal of the deduced protein there is a putative ATP binding site between amino acid residues from 233 to 414. Southern blot analysis indicated that the GbKTN1 was a single copy gene in G barbadense. Combining semi-quantitative RT-PCR with Southern blot hybridization revealed that GbKTN1 expressed in all the organs detected such as roots, stems, leaves and fibers. However, the mRNA of GbKTN1 was the most abundant in fiber cells, while it was the lowest in leaves. The GbKTN1 cDNA was transformed into S. pombe to verify its function on cell elongation. Results showed that most yeast cells over expressing GbKTN1 gene were elongated dramatically with an average length increase of 2.18 times than that of the non-induced cells. Even the morphology of some yeast cells appeared irregularly. To the best of our knowledge this is the first evidence that KTN1 is correlated with cell elongation in vivo.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
Mitochondria in many fungi are inherited uniparentally during meiosis. It has remained unclear whether parental mitochondria in the fission yeast Schizosaccharomyces pombe are inherited uniparentally or biparentally. ...Mitochondria in many fungi are inherited uniparentally during meiosis. It has remained unclear whether parental mitochondria in the fission yeast Schizosaccharomyces pombe are inherited uniparentally or biparentally. Here, we assessed the mixing of parental mitochondria carefully by live-cell microscopy and developed an algorithm to determine the degree of mitochondrial mixing in a quantitative manner. We found that parental mitochondria in fission yeast cells were mixed progressively as meiosis progressed. Moreover, we established that mitochondrial fission and the size of the conjugation neck are the limiting factors in restricting the mixing of parental mitochondria. We further employed a combination of quantitative polymerase chain reaction, fluorescent live-cell microscopy, and transmission electron microscopy approaches to examine the mitochondrial inheritance of progeny cells derived from a cross between wild-type and Rho0 (mitochondrial DNA absent) cells. The results show that all progeny cells of the cross carry mitochondrial DNA. Hence, our data support the model in which parental mitochondria in the fission yeast S. pombe are inherited biparentally during meiosis.展开更多
Based on a deterministic cell cycle model of fission yeast, the effects of the finite cell size on the cell cycle regulation in wee1- cdc25△ double mutant type are numerically studied by using of the chemical Langevi...Based on a deterministic cell cycle model of fission yeast, the effects of the finite cell size on the cell cycle regulation in wee1- cdc25△ double mutant type are numerically studied by using of the chemical Langevin equations. It is found that at a certain region of cell size, our numerical results from the chemical Langevin equations are in good qualitative agreement with the experimental observations. The two resettings to the G2 phase from early stages of mitosis can be induced under the moderate cell size. The quantized cycle times can be observed during such a cell size region. Therefore, a coarse estimation of cell size is obtained from the mesoscopic stochastic cell cycle model.展开更多
Microtubules grow not only from the centrosome but also from various noncentrosomal microtubule-organizing centers(MTOCs),including the nuclear envelope(NE)and pre-existing microtubules.The evolutionarily conserved pr...Microtubules grow not only from the centrosome but also from various noncentrosomal microtubule-organizing centers(MTOCs),including the nuclear envelope(NE)and pre-existing microtubules.The evolutionarily conserved proteins Mtol/CDK5RAP2 and Alpl4/TOG/XMAP215 have been shown to be involved in promoting microtubule nucleation.However,it has remained elusive as to how the microtubule nucleation promoting factors are specified to various noncentrosomal MTOCs,particularly the NE,and how these proteins coordinate to organize microtubule assembly.Here,we demonstrate that in the fission yeast Schizosaccharomyces pombe,efficient interphase microtubule growth from the NE requires Alp7/TACC,Alpl4/TOG/XMAP215,and Mtol/CDK5RAP2.The absence of Alp7,A lp l4 t or Mtol compromises microtubule regrowth on the NE in cells undergoing microtubule repolymerization.We further demonstrate that Alp7 and Mtol interdependently localize to the NE in cells without microtubules and that A lp l4 localizes to the NE in an Alp7 and Mtol-dependent manner.Tethering Mtol to the NE in cells lacking Alp7 partially restores microtubule number and the efficiency of microtubule generation from the NE.Hence,our study delineates that Alp7,A lpl4,and Mtol work in concert to regulate interphase microtubule regrowth on the NE.展开更多
According to the recent investigation on cell cycle of fission yeast, a mathematical dynamic model is for-mulated. Four cyclins, e.g. Puc1, Cig1, Cig2 and Cdc13, are investigated here. The interacting networks between...According to the recent investigation on cell cycle of fission yeast, a mathematical dynamic model is for-mulated. Four cyclins, e.g. Puc1, Cig1, Cig2 and Cdc13, are investigated here. The interacting networks between the cy-clins and the process of cell cycle are mathematically de-scribed. The functions of these cyclins are particularly ana-lyzed. Comparison among different mutants indicates that the cyclins play an important role in cell cycle.展开更多
基金supported by a grant from the National Natural Science Foundation of China(No.31070222)
文摘Membrane fusion is the last step in trafficking pathways during which membrane vesicles fuse with target organelles to deliver cargos. It is a central cellular reaction that plays important roles in signal transduction, protein sorting and subcellular compartmentation. Recent progress in understanding the roles of ion transporters in vacuole fusion in yeast is summarized in this article. It is becoming increasingly evident that the vacuolar proton pump V-ATPase and vacuolar Na＋/H＋ antiporter ScNhxlp are key components of the vacuole fusion machinery in yeast. Yeast ScNhxlp regulates vacuole fusion by controlling the luminal pH. V-ATPases serve a dual role in vacuolar integrity in which they regulate both vacuole fusion and fission reactions in yeast. Fission defects are epistatic to fusion defects. Vacuole fission depends on the proton translocation activity of the V-ATPase; by contrast, the fusion reaction does not need the transport activity but requires the physical presence of the proton pump. V0, the membrane-integral sector of the V-ATPase, forms trans-complexes between the opposing vacuoles in the terminal phase of vacuole fusion where the V0 trans-complexes build a continuous proteolipid channel at the fusion site to mediate the bilayer fusion.
文摘All Chinese born in the 1960's know the famous movie script "the function of a horse tail". Indeed, there is another famous "horse tail" in the field of basic biology, the premeiotic nucleus in the fission yeast Schizosaccharomyces pombe. It is not only because of its characteristic shape which looks like a horse tail, but also its dramatic oscillatory movement called "the horsetail movement". In the horsetail nucleus, all of the ends of chromosomes, the telomeres, are tightly clustering under spindle pole body (a centrosome equivalent in yeasts). Actually, this horsetail chromosome arrangement is an extreme form of so called "bouquet arrangement", a polarized chromosome arrangement with all the telomeres clustered in a confined area on the nuclear envelope. Bouquet arrangement is widely conserved meiotic prophase chromosomal phenomenon among eukaryotes. From study of the horsetail nucleus in fission yeast, many progresses have been made in the field of meiosis.
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.
文摘The GbKTN1 gene was isolated from 10 DPA fiber cells of Gossypium barbadense using 5′RACE/3′RACE.Full-length cDNA of this gene is 2006 bp, including a 113 bp of 5′untranslated region, a 1563 bp of an open reading frame(ORF), and a 327 bp of 3′untranslated region (excluding the stop codon TAA). The ORF of GbKTN1 encodes a 521-amino acid protein with a predicted size of 55 kD. Near C-terminal of the deduced protein there is a putative ATP binding site between amino acid residues from 233 to 414. Southern blot analysis indicated that the GbKTN1 was a single copy gene in G barbadense. Combining semi-quantitative RT-PCR with Southern blot hybridization revealed that GbKTN1 expressed in all the organs detected such as roots, stems, leaves and fibers. However, the mRNA of GbKTN1 was the most abundant in fiber cells, while it was the lowest in leaves. The GbKTN1 cDNA was transformed into S. pombe to verify its function on cell elongation. Results showed that most yeast cells over expressing GbKTN1 gene were elongated dramatically with an average length increase of 2.18 times than that of the non-induced cells. Even the morphology of some yeast cells appeared irregularly. To the best of our knowledge this is the first evidence that KTN1 is correlated with cell elongation in vivo.
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.
基金supported by grants from the National Natural Science Foundation of China(91754106,31621002,31871350,and 32070707)the Natural Science Key Project of Anhui Institution of Higher Education(KJ2020A0441).
文摘Mitochondria in many fungi are inherited uniparentally during meiosis. It has remained unclear whether parental mitochondria in the fission yeast Schizosaccharomyces pombe are inherited uniparentally or biparentally. Here, we assessed the mixing of parental mitochondria carefully by live-cell microscopy and developed an algorithm to determine the degree of mitochondrial mixing in a quantitative manner. We found that parental mitochondria in fission yeast cells were mixed progressively as meiosis progressed. Moreover, we established that mitochondrial fission and the size of the conjugation neck are the limiting factors in restricting the mixing of parental mitochondria. We further employed a combination of quantitative polymerase chain reaction, fluorescent live-cell microscopy, and transmission electron microscopy approaches to examine the mitochondrial inheritance of progeny cells derived from a cross between wild-type and Rho0 (mitochondrial DNA absent) cells. The results show that all progeny cells of the cross carry mitochondrial DNA. Hence, our data support the model in which parental mitochondria in the fission yeast S. pombe are inherited biparentally during meiosis.
基金Supported by the National Natural Science Foundation of China under Grant No 10575041.
文摘Based on a deterministic cell cycle model of fission yeast, the effects of the finite cell size on the cell cycle regulation in wee1- cdc25△ double mutant type are numerically studied by using of the chemical Langevin equations. It is found that at a certain region of cell size, our numerical results from the chemical Langevin equations are in good qualitative agreement with the experimental observations. The two resettings to the G2 phase from early stages of mitosis can be induced under the moderate cell size. The quantized cycle times can be observed during such a cell size region. Therefore, a coarse estimation of cell size is obtained from the mesoscopic stochastic cell cycle model.
基金the National Key Research and Development Program of China(2017YFA0503600)the National Natural Science Foundation of China(91754106,31871350,31671406,31601095,and 31621002)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB19040101)the Major/lnnovative Program of Development Foundation of Hefei Center for Physical Science and Technology(2017FXCX008)China’s 1000 Young Talents Recruitment Program.
文摘Microtubules grow not only from the centrosome but also from various noncentrosomal microtubule-organizing centers(MTOCs),including the nuclear envelope(NE)and pre-existing microtubules.The evolutionarily conserved proteins Mtol/CDK5RAP2 and Alpl4/TOG/XMAP215 have been shown to be involved in promoting microtubule nucleation.However,it has remained elusive as to how the microtubule nucleation promoting factors are specified to various noncentrosomal MTOCs,particularly the NE,and how these proteins coordinate to organize microtubule assembly.Here,we demonstrate that in the fission yeast Schizosaccharomyces pombe,efficient interphase microtubule growth from the NE requires Alp7/TACC,Alpl4/TOG/XMAP215,and Mtol/CDK5RAP2.The absence of Alp7,A lp l4 t or Mtol compromises microtubule regrowth on the NE in cells undergoing microtubule repolymerization.We further demonstrate that Alp7 and Mtol interdependently localize to the NE in cells without microtubules and that A lp l4 localizes to the NE in an Alp7 and Mtol-dependent manner.Tethering Mtol to the NE in cells lacking Alp7 partially restores microtubule number and the efficiency of microtubule generation from the NE.Hence,our study delineates that Alp7,A lpl4,and Mtol work in concert to regulate interphase microtubule regrowth on the NE.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China(Grant No.20176005).
文摘According to the recent investigation on cell cycle of fission yeast, a mathematical dynamic model is for-mulated. Four cyclins, e.g. Puc1, Cig1, Cig2 and Cdc13, are investigated here. The interacting networks between the cy-clins and the process of cell cycle are mathematically de-scribed. The functions of these cyclins are particularly ana-lyzed. Comparison among different mutants indicates that the cyclins play an important role in cell cycle.
