The self-incompatibility ( S) loci from the Solanaceae, Rosaceae and Scrophulariaceae encode a class of ribonucleases, known as S RNases, which have been shown to control the pistil expression of self-incompatible rea...The self-incompatibility ( S) loci from the Solanaceae, Rosaceae and Scrophulariaceae encode a class of ribonucleases, known as S RNases, which have been shown to control the pistil expression of self-incompatible reaction. In the former two families, the S loci have been shown to be located near centromere. However, the chromosomal location of the S locus in Antirrhinum, a species of the Scrophulariaceae, is not known. To determine its chromosomal location and genomic organization, an S-2 RNase gene and its corresponding 63 kb BAC clone were separately used for fluorescence in situ hybridization (FISH) of mitotic metaphase chromosomes of a self-incompatible Antirrhinum line Of S2S5. The results showed that the S-2 RNase detected a doublet signal near the centromere of the smallest chromosome (2n = 16). Two separate doublet signals of the tested BAC sequence were shown on both sides of the centromeres of all eight pairs of the chromosomes, suggesting that the Antirrhinum S locus is located in a pericentromeric region. Furthermore, a retrotransposon, named RIS1 (retrotransposon in the S locus), which has not been identified yet in. Antirrhinum, was found next to S-2 RNase. Taken together, the centromeric location of the S locus from the three S-RNase-based self-incompatible families provides a further support on a common origin of their evolution as well as suppressed recombination.展开更多
Mitosin/CENP-F is a human nuclear protein transiently associated with the outer kinetochore plate in M phase and is involved in M phase progression. LEK1 and CMF1, which are its murine and chicken orthologs, however, ...Mitosin/CENP-F is a human nuclear protein transiently associated with the outer kinetochore plate in M phase and is involved in M phase progression. LEK1 and CMF1, which are its murine and chicken orthologs, however, are implicated in muscle differentiation and reportedly not distributed at kinetochores.We therefore conducted several assays to clarify this issue. The typical centromere staining patterns were observed in mitotic cells from both human primary culture and murine, canine, and mink cell lines. A C-terminal portion of LEK1 also conferred centromere localization. Our analysis further suggests conserved kinetochore localization of mammalian mitosin orthologs. Moreover, mitosin was associated preferentially with kinetochores of unaligned chromosomes. It was also constantly transported from kinetochores to spindle poles by cytoplasmic dynein. These properties resemble those of other kinetochore proteins important for the spindle checkpoint, thus implying a role of mitosin in this checkpoint. Therefore, mitosin family may serve as multifunctional proteins involved in both mitosis and differentiation.展开更多
For proper chromosome segregation, all kinetochores must achieve bipolar microtubule （MT） attachment and subsequently align at the spindle equator before anaphase onset. The MT minus end-directed motor dynein/dynact...For proper chromosome segregation, all kinetochores must achieve bipolar microtubule （MT） attachment and subsequently align at the spindle equator before anaphase onset. The MT minus end-directed motor dynein/dynactin binds kinetoehores in prometaphase and has long been implicated in chromosome congression. Unfortunately, inactivation of dynein usually disturbs spindle organization, thus hampering evaluation of its kinetochore roles. Here we specifically eliminated kinetochore dynein/dynactin by RNAi-mediated depletion of ZW10, a protein essential for kinetochore localization of the motor. Time-lapse microscopy indicated markedly-reduced congression efficiency, though congressing chromosomes displayed similar velocities as in control cells. Moreover, cells frequently failed to achieve full chromosome alignment, despite their normal spindles. Confocal microcopy revealed that the misaligned kinetochores were monooriented or unattached and mostly lying outside the spindle, suggesting a difficulty to capture MTs from the opposite pole. Kinetoehores on monoastral spindles were dispersed farther away from the pole and exhibited only mild oscillation. Furthermore, inactivating dynein by other means generated similar phenotypes. Therefore, kinetochore dynein produces on monooriented kinetochores a poleward pulling force, which may contribute to efficient bipolar attachment by facilitating their proper microtubule captures to promote congression as well as full chromosome alignment.展开更多
Chromosome segregation in mitosis is orchestrated by the interaction of the kinetochore with spindle microtubules. Our recent study shows that NEK2A interacts with MAD 1 at the kinetochore and possibly functions as a ...Chromosome segregation in mitosis is orchestrated by the interaction of the kinetochore with spindle microtubules. Our recent study shows that NEK2A interacts with MAD 1 at the kinetochore and possibly functions as a novel integrator of spindle checkpoint signaling. However, it is unclear how NEK2A regulates kinetochore-microtubule attachment in mitosis. Here we show that NEK2A phosphorylates human Sgo 1 and such phosphorylation is essential for faithful chromosome congression in mitosis. NEK2A binds directly to HsSgol in vitro and co-distributes with HsSgol to the kinetochore of mitotic cells. Our in vitro phosphorylation experiment demonstrated that HsSgo 1 is a substrate of NEK2A and the phosphorylation sites were mapped to Ser^14 and Ser^507 as judged by the incorporation of 32^P. Although such phosphorylation is not required for assembly of HsSgo 1 to the kinetochore, expression of non-phosphorylatable mutant HsSgo 1 perturbed chromosome congression and resulted in a dramatic increase in microtubule attachment errors, including syntelic and monotelic attachments. These findings reveal a key role for the NEK2A-mediated phosphorylation ofHsSgo 1 in orchestrating dynamic kinetochore-microtubule interaction. We propose that NEK2A-mediated phosphorylation of human Sgo 1 provides a link between centromeric cohesion and spindle microtubule attachment at the kinetochores.展开更多
Cyclin B1 is a key regulatory protein controlling cell cycle progression in vertebrates. Cyclin B1 binds CDK1, a cy-clin-dependent kinase catalytic subunit, forming a complex that orchestrates mitosis through phosphor...Cyclin B1 is a key regulatory protein controlling cell cycle progression in vertebrates. Cyclin B1 binds CDK1, a cy-clin-dependent kinase catalytic subunit, forming a complex that orchestrates mitosis through phosphorylation of key proteins. Cyclin B1 regulates both the activation of CDK1 and its subcellular localization, which may be critical for substrate selection. Here, we demonstrate that cyclin B1 is concentrated on the outer plate of the kinetochore during prometaphase. This localization requires the cyclin box region of the protein. Cyclin B1 is displaced from individual kinetochores to the spindle poles by microtubule attachment to the kinetochores, and this displacement is dependent on the dynein/dynactin complex. Depletion of cyclin B1 by vector-based siRNA causes inefficient attachment between kinetochores and microtubules, and chromosome alignment defects, and delays the onset of anaphase. We conclude that cyclin B1 accumulates at kinetochores during prometaphase, where it contributes to the correct attachment of mi- crotubules to kinetochores and efficient alignment of the chromosomes, most likely through localized phosphorylation of specific substrates by cyclin B1-CDK1. Cyclin B1 is then transported from each kinetochore as microtubule attachment is completed, and this relocalization may redirect the activity of cyclin B1-CDK1 and contribute to inactivation of the spindle assembly checkpoint.展开更多
Let G be a simple graph and f be a proper total kcoloring of G. The color set of each vertex v of G is the set of colors appearing on v and the edges incident to v. The coloring f is said to be an adjacent vertex-dist...Let G be a simple graph and f be a proper total kcoloring of G. The color set of each vertex v of G is the set of colors appearing on v and the edges incident to v. The coloring f is said to be an adjacent vertex-distinguishing total coloring if the color sets of any two adjacent vertices are distinct. The minimum k for which such a coloring of G exists is called the adjacent vertex-distinguishing total chromatic number of G. The join graph of two vertex-disjoint graphs is the graph union of these two graphs together with all the edges that connect the vertices of one graph with the vertices of the other. The adjacent vertex-distinguishing total chromatic numbers of the join graphs of an empty graph of order s and a complete graph of order t are determined.展开更多
L(d, 1)-labeling is a kind of graph coloring problem from frequency assignment in radio networks, in which adjacent nodes must receive colors that are at least d apart while nodes at distance two from each other must ...L(d, 1)-labeling is a kind of graph coloring problem from frequency assignment in radio networks, in which adjacent nodes must receive colors that are at least d apart while nodes at distance two from each other must receive different colors. We focus on L(d, 1)-labeling of regular tilings for d≥3 since the cases d=0, 1 or 2 have been researched by Calamoneri and Petreschi. For all three kinds of regular tilings, we give their L (d, 1)-labeling numbers for any integer d≥3. Therefore, combined with the results given by Calamoneri and Petreschi, the L(d, 1)-labeling numbers of regular tilings for any nonnegative integer d may be determined completely.展开更多
The kinetochore composition of rat liver cells was studied by indirect immunofluorescence andimmunoblotting using human anti-kinetochore/centromere autoantibodies(ACAs).Besides threemajor antigens(50kD,42 kD and 34 kD...The kinetochore composition of rat liver cells was studied by indirect immunofluorescence andimmunoblotting using human anti-kinetochore/centromere autoantibodies(ACAs).Besides threemajor antigens(50kD,42 kD and 34 kD),ACAs used in this study could also identify those of 32-30 kD and 20 kD in newborn rat liver cells,90 kD in old rat liver cells,37 kD and 32-30 kD inregenerating liver cells.These results indicate that some kinetochore antigen(s)may be related to cellproliferation or specific for different stages of development.展开更多
文摘The self-incompatibility ( S) loci from the Solanaceae, Rosaceae and Scrophulariaceae encode a class of ribonucleases, known as S RNases, which have been shown to control the pistil expression of self-incompatible reaction. In the former two families, the S loci have been shown to be located near centromere. However, the chromosomal location of the S locus in Antirrhinum, a species of the Scrophulariaceae, is not known. To determine its chromosomal location and genomic organization, an S-2 RNase gene and its corresponding 63 kb BAC clone were separately used for fluorescence in situ hybridization (FISH) of mitotic metaphase chromosomes of a self-incompatible Antirrhinum line Of S2S5. The results showed that the S-2 RNase detected a doublet signal near the centromere of the smallest chromosome (2n = 16). Two separate doublet signals of the tested BAC sequence were shown on both sides of the centromeres of all eight pairs of the chromosomes, suggesting that the Antirrhinum S locus is located in a pericentromeric region. Furthermore, a retrotransposon, named RIS1 (retrotransposon in the S locus), which has not been identified yet in. Antirrhinum, was found next to S-2 RNase. Taken together, the centromeric location of the S locus from the three S-RNase-based self-incompatible families provides a further support on a common origin of their evolution as well as suppressed recombination.
基金supported by grants 97JC14006 from Shanghai Committee of Science and Technology(No.30025021,39970160,and 39500030)from the Natural Science Foundation of ChinaKSCX2-2-02 from Chinese Academy of Sciences.
文摘Mitosin/CENP-F is a human nuclear protein transiently associated with the outer kinetochore plate in M phase and is involved in M phase progression. LEK1 and CMF1, which are its murine and chicken orthologs, however, are implicated in muscle differentiation and reportedly not distributed at kinetochores.We therefore conducted several assays to clarify this issue. The typical centromere staining patterns were observed in mitotic cells from both human primary culture and murine, canine, and mink cell lines. A C-terminal portion of LEK1 also conferred centromere localization. Our analysis further suggests conserved kinetochore localization of mammalian mitosin orthologs. Moreover, mitosin was associated preferentially with kinetochores of unaligned chromosomes. It was also constantly transported from kinetochores to spindle poles by cytoplasmic dynein. These properties resemble those of other kinetochore proteins important for the spindle checkpoint, thus implying a role of mitosin in this checkpoint. Therefore, mitosin family may serve as multifunctional proteins involved in both mitosis and differentiation.
基金Acknowledgments The authors thank Qiongping Huang, Lirong Liu, and Wei Bian for technical assistance. We are grateful to Drs G Chan （Cross Cancer Institute, University of Alberta, Edmonton Alberta, Canada） for antibodies to human ZW 10 and Rod, KH Choo （Murdoch Children＇s Research Institute, Royal Children＇s Hospital, Melbourne, Australia） for anti-CREST serum, and E Fuchs （Rockefeller University, USA） for mRFP cDNA. This work was supported by the National Science Foundation of China （30330330, 30421005, and 30623003）, Ministry of Science and Technology of China （2005CB522703 and 2007CB914501）, and the Shanghai Municipal Council for Science and Technology （S048014317, 06DZ22032, and 058014578）.
文摘For proper chromosome segregation, all kinetochores must achieve bipolar microtubule （MT） attachment and subsequently align at the spindle equator before anaphase onset. The MT minus end-directed motor dynein/dynactin binds kinetoehores in prometaphase and has long been implicated in chromosome congression. Unfortunately, inactivation of dynein usually disturbs spindle organization, thus hampering evaluation of its kinetochore roles. Here we specifically eliminated kinetochore dynein/dynactin by RNAi-mediated depletion of ZW10, a protein essential for kinetochore localization of the motor. Time-lapse microscopy indicated markedly-reduced congression efficiency, though congressing chromosomes displayed similar velocities as in control cells. Moreover, cells frequently failed to achieve full chromosome alignment, despite their normal spindles. Confocal microcopy revealed that the misaligned kinetochores were monooriented or unattached and mostly lying outside the spindle, suggesting a difficulty to capture MTs from the opposite pole. Kinetoehores on monoastral spindles were dispersed farther away from the pole and exhibited only mild oscillation. Furthermore, inactivating dynein by other means generated similar phenotypes. Therefore, kinetochore dynein produces on monooriented kinetochores a poleward pulling force, which may contribute to efficient bipolar attachment by facilitating their proper microtubule captures to promote congression as well as full chromosome alignment.
基金We thank members of our group for insightful discussion during the course of this study.This work was supported by grants from Chinese Academy of Science(KSCX1-YW-R65,KSCX2-YW-H10)National Basic Research Program of China(2002CB713700)+4 种基金Hi-Tech Research and Development Program of China(2001AA215331)Chinese Minister of Education(20020358051 to XY,PCSIRT0413 to XD)National Natural Science Foundation of China(39925018,30270293 to XY,30500183 to XD,30600222 to JY)National Institutes of Health(USA)(DK56292,CA92080)to XY(a Georgia Cancer Coalition Eminent Scholar)JY was supported by China Postdoctor(2005037560).
文摘Chromosome segregation in mitosis is orchestrated by the interaction of the kinetochore with spindle microtubules. Our recent study shows that NEK2A interacts with MAD 1 at the kinetochore and possibly functions as a novel integrator of spindle checkpoint signaling. However, it is unclear how NEK2A regulates kinetochore-microtubule attachment in mitosis. Here we show that NEK2A phosphorylates human Sgo 1 and such phosphorylation is essential for faithful chromosome congression in mitosis. NEK2A binds directly to HsSgol in vitro and co-distributes with HsSgol to the kinetochore of mitotic cells. Our in vitro phosphorylation experiment demonstrated that HsSgo 1 is a substrate of NEK2A and the phosphorylation sites were mapped to Ser^14 and Ser^507 as judged by the incorporation of 32^P. Although such phosphorylation is not required for assembly of HsSgo 1 to the kinetochore, expression of non-phosphorylatable mutant HsSgo 1 perturbed chromosome congression and resulted in a dramatic increase in microtubule attachment errors, including syntelic and monotelic attachments. These findings reveal a key role for the NEK2A-mediated phosphorylation ofHsSgo 1 in orchestrating dynamic kinetochore-microtubule interaction. We propose that NEK2A-mediated phosphorylation of human Sgo 1 provides a link between centromeric cohesion and spindle microtubule attachment at the kinetochores.
文摘Cyclin B1 is a key regulatory protein controlling cell cycle progression in vertebrates. Cyclin B1 binds CDK1, a cy-clin-dependent kinase catalytic subunit, forming a complex that orchestrates mitosis through phosphorylation of key proteins. Cyclin B1 regulates both the activation of CDK1 and its subcellular localization, which may be critical for substrate selection. Here, we demonstrate that cyclin B1 is concentrated on the outer plate of the kinetochore during prometaphase. This localization requires the cyclin box region of the protein. Cyclin B1 is displaced from individual kinetochores to the spindle poles by microtubule attachment to the kinetochores, and this displacement is dependent on the dynein/dynactin complex. Depletion of cyclin B1 by vector-based siRNA causes inefficient attachment between kinetochores and microtubules, and chromosome alignment defects, and delays the onset of anaphase. We conclude that cyclin B1 accumulates at kinetochores during prometaphase, where it contributes to the correct attachment of mi- crotubules to kinetochores and efficient alignment of the chromosomes, most likely through localized phosphorylation of specific substrates by cyclin B1-CDK1. Cyclin B1 is then transported from each kinetochore as microtubule attachment is completed, and this relocalization may redirect the activity of cyclin B1-CDK1 and contribute to inactivation of the spindle assembly checkpoint.
基金The Fundamental Research Funds for the Central Universities of China(No.3207013904)
文摘Let G be a simple graph and f be a proper total kcoloring of G. The color set of each vertex v of G is the set of colors appearing on v and the edges incident to v. The coloring f is said to be an adjacent vertex-distinguishing total coloring if the color sets of any two adjacent vertices are distinct. The minimum k for which such a coloring of G exists is called the adjacent vertex-distinguishing total chromatic number of G. The join graph of two vertex-disjoint graphs is the graph union of these two graphs together with all the edges that connect the vertices of one graph with the vertices of the other. The adjacent vertex-distinguishing total chromatic numbers of the join graphs of an empty graph of order s and a complete graph of order t are determined.
文摘L(d, 1)-labeling is a kind of graph coloring problem from frequency assignment in radio networks, in which adjacent nodes must receive colors that are at least d apart while nodes at distance two from each other must receive different colors. We focus on L(d, 1)-labeling of regular tilings for d≥3 since the cases d=0, 1 or 2 have been researched by Calamoneri and Petreschi. For all three kinds of regular tilings, we give their L (d, 1)-labeling numbers for any integer d≥3. Therefore, combined with the results given by Calamoneri and Petreschi, the L(d, 1)-labeling numbers of regular tilings for any nonnegative integer d may be determined completely.
基金This work was supported by the National Natural Science Foundation of China
文摘The kinetochore composition of rat liver cells was studied by indirect immunofluorescence andimmunoblotting using human anti-kinetochore/centromere autoantibodies(ACAs).Besides threemajor antigens(50kD,42 kD and 34 kD),ACAs used in this study could also identify those of 32-30 kD and 20 kD in newborn rat liver cells,90 kD in old rat liver cells,37 kD and 32-30 kD inregenerating liver cells.These results indicate that some kinetochore antigen(s)may be related to cellproliferation or specific for different stages of development.
