Components of the human spindle checkpoint control mechanism localize specifically to the active centromere on dicentric chromosomes

2000 ◽  
Vol 107 (4) ◽  
pp. 376-384 ◽  
Author(s):  
Richard Saffery ◽  
Danielle Irvine ◽  
Belinda Griffiths ◽  
Paul Kalitsis ◽  
K. Choo
Keyword(s):  
Control Mechanism ◽  
Spindle Checkpoint ◽  
Checkpoint Control ◽  
Dicentric Chromosomes ◽  
Active Centromere

HZwint-1, a novel human kinetochore component that interacts with HZW10

2000 ◽  
Vol 113 (11) ◽  
pp. 1939-1950 ◽  
Author(s):  
D.A. Starr ◽  
R. Saffery ◽  
Z. Li ◽  
A.E. Simpson ◽  
K.H. Choo ◽  
...  
Keyword(s):  
Hela Cells ◽  
Coiled Coil ◽  
Yeast Two Hybrid ◽  
Interacting Protein ◽  
Dicentric Chromosomes ◽  
Centromere Function ◽  
Coiled Coil Domain ◽  
Gfp Fluorescence ◽  
Two Hybrid ◽  
Active Centromere

HZwint-1 (Human ZW10 interacting protein-1) was identified in a yeast two hybrid screen for proteins that interact with HZW10. HZwint-1 cDNA encodes a 43 kDa protein predicted to contain an extended coiled-coil domain. Immunofluorescence studies with sera raised against HZwint-1 protein revealed strong kinetochore staining in nocodazole-arrested chromosome spreads. This signal co-localizes at the kinetochore with HZW10, at a position slightly outside of the central part of the centromere as revealed by staining with a CREST serum. The kinetochore localization of HZwint-1 has been confirmed by following GFP fluorescence in HeLa cells transiently transfected with a plasmid encoding a GFP/HZwint-1 fusion protein. In cycling HeLa cells, HZwint-1 localizes to the kinetochore of prophase HeLa cells prior to HZW10 localization, and remains at the kinetochore until late in anaphase. This localization pattern, combined with the two-hybrid results, suggests that HZwint-1 may play a role in targeting HZW10 to the kinetochore at prometaphase. HZwint-1 was also found to localize to neocentromeres and to the active centromere of dicentric chromosomes. HZwint-1 thus appears to associate with all active centromeres, implying that it plays an important role in correct centromere function.

scholarly journals DNA Replication Checkpoint Control Mediated by the Spindle Checkpoint Protein Mad2p in Fission Yeast

2004 ◽  
Vol 279 (45) ◽  
pp. 47372-47378 ◽  
Author(s):  
Izumi Sugimoto ◽  
Hiroshi Murakami ◽  
Yuko Tonami ◽  
Akihiko Moriyama ◽  
Makoto Nakanishi
Keyword(s):  
Dna Replication ◽  
Fission Yeast ◽  
Spindle Checkpoint ◽  
Checkpoint Control ◽  
Replication Checkpoint ◽  
Checkpoint Protein ◽  
Dna Replication Checkpoint

scholarly journals Human Papillomavirus Oncoproteins E6 and E7 Independently Abrogate the Mitotic Spindle Checkpoint

1998 ◽  
Vol 72 (2) ◽  
pp. 1131-1137 ◽  
Author(s):  
Jennifer T. Thomas ◽  
Laimonis A. Laimins
Keyword(s):  
Human Papillomavirus ◽  
High Risk ◽  
Mitotic Spindle ◽  
Spindle Checkpoint ◽  
Human Keratinocytes ◽  
Mitotic Checkpoint ◽  
Cell Cycle Checkpoint ◽  
Checkpoint Control ◽  
Mitotic Spindle Checkpoint ◽  
E6 And E7

ABSTRACT The E6 and E7 genes of the high-risk human papillomavirus (HPV) types encode oncoproteins, and both act by interfering with the activity of cellular tumor suppressor proteins. E7 proteins act by associating with members of the retinoblastoma family, while E6 increases the turnover of p53. p53 has been implicated as a regulator of both the G1/S cell cycle checkpoint and the mitotic spindle checkpoint. When fibroblasts from p53 knockout mice are treated with the spindle inhibitor nocodazole, a rereplication of DNA occurs without transit through mitosis. We investigated whether E6 or E7 could induce a similar loss of mitotic checkpoint activity in human keratinocytes. Recombinant retroviruses expressing high-risk E6 alone, E7 alone, and E6 in combination with E7 were used to infect normal human foreskin keratinocytes (HFKs). Established cell lines were treated with nocodazole, stained with propidium iodide, and analyzed for DNA content by flow cytometry. Cells infected with high-risk E6 were found to continue to replicate DNA and accumulated an octaploid (8N) population. Surprisingly, expression of E7 alone was also able to bypass this checkpoint. Cells expressing E7 alone exhibited increased levels of p53, while those expressing E6 had significantly reduced levels. The p53 present in the E7 cells was active, as increased levels of p21 were observed. This suggested that E7 bypassed the mitotic checkpoint by a p53-independent mechanism. The levels of MDM2, a cellular oncoprotein also implicated in control of the mitotic checkpoint, were significantly elevated in the E7 cells compared to the normal HFKs. In E6-expressing cells, the levels of MDM2 were undetectable. It is possible that abrogation of Rb function by E7 or increased expression of MDM2 contributes to the loss of mitotic spindle checkpoint control in the E7 cells. These findings suggest mechanisms by which both HPV oncoproteins contribute to genomic instability at the mitotic checkpoint.

scholarly journals A checkpoint control orchestrates the replication of the two chromosomes of Vibrio cholerae

2016 ◽  
Vol 2 (4) ◽  
pp. e1501914 ◽  
Author(s):  
Marie-Eve Val ◽  
Martial Marbouty ◽  
Francisco de Lemos Martins ◽  
Sean P. Kennedy ◽  
Harry Kemble ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Vibrio Cholerae ◽  
Control Mechanism ◽  
Bacterial Species ◽  
Chromosome Replication ◽  
Replication Initiation ◽  
Checkpoint Control ◽  
Initiation Mechanism ◽  
Functional Interactions ◽  
Circular Chromosomes

Bacteria with multiple chromosomes represent up to 10% of all bacterial species. Unlike eukaryotes, these bacteria use chromosome-specific initiators for their replication. In all cases investigated, the machineries for secondary chromosome replication initiation are of plasmid origin. One of the important differences between plasmids and chromosomes is that the latter replicate during a defined period of the cell cycle, ensuring a single round of replication per cell. Vibrio cholerae carries two circular chromosomes, Chr1 and Chr2, which are replicated in a well-orchestrated manner with the cell cycle and coordinated in such a way that replication termination occurs at the same time. However, the mechanism coordinating this synchrony remains speculative. We investigated this mechanism and revealed that initiation of Chr2 replication is triggered by the replication of a 150-bp locus positioned on Chr1, called crtS. This crtS replication–mediated Chr2 replication initiation mechanism explains how the two chromosomes communicate to coordinate their replication. Our study reveals a new checkpoint control mechanism in bacteria, and highlights possible functional interactions mediated by contacts between two chromosomes, an unprecedented observation in bacteria.

scholarly journals The APC/C recruits cyclin B1–Cdk1–Cks in prometaphase before D box recognition to control mitotic exit

2010 ◽  
Vol 190 (4) ◽  
pp. 587-602 ◽  
Author(s):  
Wouter van Zon ◽  
Janneke Ogink ◽  
Bas ter Riet ◽  
René H. Medema ◽  
Hein te Riele ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Spindle Checkpoint ◽  
Cyclin A ◽  
Cyclin B1 ◽  
Mitotic Exit ◽  
Dependent Manner ◽  
Anaphase Promoting Complex ◽  
Checkpoint Control ◽  
N Terminus ◽  
Mitotic Phosphorylation

The ubiquitin ligase anaphase-promoting complex/cyclosome (APC/C) is activated at prometaphase by mitotic phosphorylation and binding of its activator, Cdc20. This initiates cyclin A degradation, whereas cyclin B1 is stabilized by the spindle checkpoint. Upon checkpoint release, the RXXL destruction box (D box) was proposed to direct cyclin B1 to core APC/C or Cdc20. In this study, we report that endogenous cyclin B1–Cdk1 is recruited to checkpoint-inhibited, phosphorylated APC/C in prometaphase independently of Cdc20 or the cyclin B1 D box. Like cyclin A, cyclin B1 binds the APC/C by the Cdk cofactor Cks and the APC3 subunit. Prior binding to APC/CCdc20 makes cyclin B1 a better APC/C substrate in metaphase, driving mitotic exit and cytokinesis. We conclude that in prometaphase, the phosphorylated APC/C can recruit both cyclin A and cyclin B1 in a Cks-dependent manner. This suggests that the spindle checkpoint blocks D box recognition of APC/C-bound cyclin B1, whereas distinctive complexes between the N terminus of cyclin A and Cdc20 evade checkpoint control.

How oocytes try to get it right: spindle checkpoint control in meiosis

Chromosoma ◽  
2015 ◽  
Vol 125 (2) ◽  
pp. 321-335 ◽  
Author(s):  
Sandra A. Touati ◽  
Katja Wassmann
Keyword(s):  
Spindle Checkpoint ◽  
Checkpoint Control

scholarly journals Functional Redundancy in the Maize Meiotic Kinetochore

2000 ◽  
Vol 151 (1) ◽  
pp. 131-142 ◽  
Author(s):  
Hong-Guo Yu ◽  
R. Kelly Dawe
Keyword(s):  
Light Microscopy ◽  
Chromosome Segregation ◽  
Spindle Checkpoint ◽  
Functional Redundancy ◽  
Checkpoint Control ◽  
Checkpoint Proteins ◽  
Spindle Poles ◽  
Division 1 ◽  
Sister Kinetochore ◽  
Meiosis I

Kinetochores can be thought of as having three major functions in chromosome segregation: (a) moving plateward at prometaphase; (b) participating in spindle checkpoint control; and (c) moving poleward at anaphase. Normally, kinetochores cooperate with opposed sister kinetochores (mitosis, meiosis II) or paired homologous kinetochores (meiosis I) to carry out these functions. Here we exploit three- and four-dimensional light microscopy and the maize meiotic mutant absence of first division 1 (afd1) to investigate the properties of single kinetochores. As an outcome of premature sister kinetochore separation in afd1 meiocytes, all of the chromosomes at meiosis II carry single kinetochores. Approximately 60% of the single kinetochore chromosomes align at the spindle equator during prometaphase/metaphase II, whereas acentric fragments, also generated by afd1, fail to align at the equator. Immunocytochemistry suggests that the plateward movement occurs in part because the single kinetochores separate into half kinetochore units. Single kinetochores stain positive for spindle checkpoint proteins during prometaphase, but lose their staining as tension is applied to the half kinetochores. At anaphase, ∼6% of the kinetochores develop stable interactions with microtubules (kinetochore fibers) from both spindle poles. Our data indicate that maize meiotic kinetochores are plastic, redundant structures that can carry out each of their major functions in duplicate.

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