scholarly journals The Condensin Complex Is Essential for Amitotic Segregation of Bulk Chromosomes, but Not Nucleoli, in the Ciliate Tetrahymena thermophila

2006 ◽  
Vol 26 (12) ◽  
pp. 4690-4700 ◽  
Author(s):  
Marcella D. Cervantes ◽  
Robert S. Coyne ◽  
Xiaohui Xi ◽  
Meng-Chao Yao
Keyword(s):  
Nuclear Division ◽  
Tetrahymena Thermophila ◽  
Chromatin Condensation ◽  
Core Component ◽  
Normal Cells ◽  
Dna Segregation ◽  
Daughter Cells ◽  
Condensin Complex ◽  
Random Segregation ◽  
Nucleolar Segregation

ABSTRACT The macronucleus of the binucleate ciliate Tetrahymena thermophila contains fragmented and amplified chromosomes that do not have centromeres, eliminating the possibility of mitotic nuclear division. Instead, the macronucleus divides by amitosis with random segregation of these chromosomes without detectable chromatin condensation. This amitotic division provides a special opportunity for studying the roles of mitotic proteins in segregating acentric chromatin. The Smc4 protein is a core component of the condensin complex that plays a role in chromatin condensation and has also been associated with nucleolar segregation, DNA repair, and maintenance of the chromatin scaffold. Mutants of Tetrahymena SMC4 have remarkable characteristics during amitosis. They do not form microtubules inside the macronucleus as normal cells do, and there is little or no bulk DNA segregation during cell division. Nevertheless, segregation of nucleoli to daughter cells still occurs, indicating the independence of this process and bulk DNA segregation in ciliate amitosis.

scholarly journals A specialized condensin complex participates in somatic nuclear maturation in Tetrahymena thermophila

2019 ◽  
Vol 30 (11) ◽  
pp. 1326-1338 ◽  
Author(s):  
Rachel Howard-Till ◽  
Miao Tian ◽  
Josef Loidl
Keyword(s):  
Sexual Reproduction ◽  
Chromatin Remodeling ◽  
Nuclear Division ◽  
Tetrahymena Thermophila ◽  
Vegetative Cells ◽  
Nuclear Maturation ◽  
The Core ◽  
Condensin Complex ◽  
Chromatin Remodeling Complex ◽  
Putative Member

Condensins are highly conserved proteins that are important for chromosome maintenance in nearly all forms of life. Although many organisms employ two forms of the condensin complex, the condensin genes in Tetrahymena have expanded even further. Here we report a form of condensin that is specifically active during sexual reproduction. This complex, condensin D, is composed of the core condensin proteins, Smc2 and Smc4, and two unique subunits, the kleisin Cph5 and Cpd2. Cpd2 is also found in somatic nuclei in vegetative cells, but is dispensable for growth and nuclear division. Immunoprecipitation experiments show that condensin D interacts with a putative member of a chromatin-remodeling complex during development. Condensin D is required for sexual reproduction and for endoreplication and genome reduction of the progeny’s somatic nuclei. Altogether, Tetrahymena possesses at least four forms of condensin to fulfill the needs of maintaining chromosomes in two different nuclei containing the somatic and germline genomes.

scholarly journals The Exon Junction Complex Core Represses Cancer-Specific Mature mRNA Re-Splicing: A Potential Key Role in Terminating Splicing

2021 ◽  
Vol 22 (12) ◽  
pp. 6519
Author(s):  
Yuta Otani ◽  
Ken-ichi Fujita ◽  
Toshiki Kameyama ◽  
Akila Mayeda
Keyword(s):  
Cancer Cells ◽  
Control Factor ◽  
Exon Junction Complex ◽  
Core Component ◽  
Normal Cells ◽  
Knock Down ◽  
Exon Junction ◽  
Mature Mrna ◽  
Complex Core ◽  
Specific Mrna

Using TSG101 pre-mRNA, we previously discovered cancer-specific re-splicing of mature mRNA that generates aberrant transcripts/proteins. The fact that mRNA is aberrantly re-spliced in various cancer cells implies there must be an important mechanism to prevent deleterious re-splicing on the spliced mRNA in normal cells. We thus postulated that mRNA re-splicing is controlled by specific repressors, and we searched for repressor candidates by siRNA-based screening for mRNA re-splicing activity. We found that knock-down of EIF4A3, which is a core component of the exon junction complex (EJC), significantly promoted mRNA re-splicing. Remarkably, we could recapitulate cancer-specific mRNA re-splicing in normal cells by knock-down of any of the core EJC proteins, EIF4A3, MAGOH, or RBM8A (Y14), implicating the EJC core as the repressor of mRNA re-splicing often observed in cancer cells. We propose that the EJC core is a critical mRNA quality control factor to prevent over-splicing of mature mRNA.

Apoptin Induces Chromatin Condensation in Normal Cells

Virus Genes ◽  
2005 ◽  
Vol 31 (1) ◽  
pp. 49-55 ◽  
Author(s):  
Xiangjun He ◽  
Qi Zhang ◽  
Yujing Liu ◽  
Peiying He
Keyword(s):  
Chromatin Condensation ◽  
Normal Cells

scholarly journals Sex, amitosis, and evolvability in the ciliate Tetrahymena thermophila

2021 ◽  
Author(s):  
Jason A Tarkington ◽  
Hao Zhang ◽  
Ricardo Azevedo ◽  
Rebecca Zufall
Keyword(s):  
Genetic Variation ◽  
Experimental Evolution ◽  
Evolutionary Biology ◽  
Genetic Architecture ◽  
Nuclear Division ◽  
Tetrahymena Thermophila ◽  
Laboratory Populations ◽  
Evolutionary Success ◽  
Sexual Progeny ◽  
Open Question

Understanding the mechanisms that generate genetic variation, and thus contribute to the process of adaptation, is a major goal of evolutionary biology. Mutation and genetic exchange have been well studied as mechanisms to generate genetic variation. However, there are additional processes that may also generate substantial genetic variation in some populations and the extent to which these variation generating mechanisms are themselves shaped by natural selection is still an open question. Tetrahymena thermophila is a ciliate with an unusual mechanism of nuclear division, called amitosis, which can generate genetic variation among the asexual descendants of a newly produced sexual progeny. We hypothesize that amitosis thus increases the evolvability of newly produced sexual progeny relative to species that undergo mitosis. To test this hypothesis, we used experimental evolution and simulations to compare the rate of adaptation in T. thermophila populations founded by a single sexual progeny to parental populations that had not had sex in many generations. The populations founded by a sexual progeny adapted more quickly than parental populations in both laboratory populations and simulated populations. This suggests that the additional genetic variation generated by amitosis of a heterozygote can increase the rate of adaptation following sex and may help explain the evolutionary success of the unusual genetic architecture of Tetrahymena and ciliates more generally.

scholarly journals Is the effect of Decitabine limited to hypomethylation and DNMTs?

2019 ◽  
Author(s):  
Sina Dalvand ◽  
Amin Namdari ◽  
Ashraf Alemi ◽  
Mohammad Hassan Meshkibaf ◽  
Sam Setayesh ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mrna Expression ◽  
Histone Deacetylases ◽  
Dna Methyltransferase ◽  
Chromatin Condensation ◽  
Dna Demethylation ◽  
Histone Tails ◽  
Normal Cells ◽  
Before And After ◽  
Cancerous Cells

Abstract Background: Histone modifications play a crucial role in chromatin structure. Among enzymes, which regulate these processes, histone deacetylases (HDACs) can remove acetyl groups from histone tails, thus increasing their interaction with DNA and leading to chromatin condensation. 5-Aza-2′-deoxycytidine (AZad) or Decitabine is a potent hypomethylating agent that incorporates into DNA and traps DNA methyltransferase in the form of a covalent protein–DNA adduct. Azad, not only change the gene expression through demethylation of the gene's promoter, but it also can change gene expression independently from DNA demethylation. So, the present study was to distinguish whether AZad in addition to inhibitory effects on DNA methyltransferase, can change HDAC3 and HDAC7 mRNA expression in NALM-6, HL-60 cancer cell lines. Methods: HL-60, NALM-6 and normal cells were cultured, and the treatment dose of the AZad was obtained (1µM) by the MTT test. Finally, HDAC3 and HDAC7 mRNA expression were measured by Real Time PCR in HL-60 and NALM-6 cancerous cells before and after treatment. In addition, HDAC3 and HDAC7 mRNA expression in un-treated HL-60 and NALM-6 cancerous cells were compared to the normal cells. Results: Our result revealed that expression of HDAC3 and HDAC7, in HL-60 and NALM-6 cells increases as compared to normal cells. After treatment of HL-60 and NALM-6 cells with AZad, HDAC3 and HDAC7 mRNA expression were decreased significantly. Conclusions: Our data showed, the effects of AZad are not limited to direct hypomethylation of DNMTs but it can indirectly affect other epigenetic factors, such as HDACs activity, through converging pathways. Keywords: HDAC3 ; HDAC7 ; HL-60; NALM-6 ; Decitabine ; AZad

Effect of cytochalasin B on somatic cell hybrids between normal and transformed cells

1985 ◽  
Vol 78 (1) ◽  
pp. 87-96
Author(s):  
I. Hickey ◽  
C. McConville ◽  
M. McMenamin ◽  
R. Neill
Keyword(s):  
Dna Synthesis ◽  
Somatic Cell ◽  
Cytochalasin B ◽  
Nuclear Division ◽  
Transformed Cells ◽  
Somatic Cell Hybrids ◽  
Recessive Character ◽  
Normal Cells ◽  
Cell Hybrids ◽  
Transformed Cell Lines

Cytochalasin B (CB) prevents cytokinesis in animal cells. In normal cells nuclear division and DNA synthesis are also blocked and the cells, held in the G1 phase of the cell cycle, remain either mononucleate or binucleate. In transformed cell lines DNA synthesis and nuclear division continue and the cells become multinucleate. We have examined the response to CB in two sets of somatic cell hybrids made between cells that display multinucleation after CB treatment and cells that do not. In a cross between transformed mouse LMTK cells and normal rat embryo lung cells, very little multinucleation was observed after treatment with CB for 7 days. The ability of the LMTK cells to form clones in soft agar was also significantly reduced in these hybrids. Segregant sub-clones that re-expressed both of these transformation phenotypes were isolated. These had reduced chromosome numbers. A second cross was made between two variants of the BHK cell line, one of which displayed a high level of multinucleation in CB while the other did not. Again the hybrids showed a response similar to that of the non-multinucleating parent. From the results obtained with these two hybrids we conclude that the multinucleation induced in transformed cells by CB behaves as a recessive character in crosses with normal cells.

Hyperplasia: The spread of abnormal cells through a plane lattice

1971 ◽  
Vol 3 (2) ◽  
pp. 210-211 ◽  
Author(s):  
Trevor Williams ◽  
Rolf Bjerknes
Keyword(s):  
Basement Membrane ◽  
Basal Cell ◽  
Basal Layer ◽  
Normal Cells ◽  
Daughter Cells ◽  
Plane Lattice ◽  
Abnormal Cells ◽  
A Cell

When a basal cell divides, both daughter cells remain in the basal layer of the epithelium, with one of the neighbouring cells being pushed out to make room. This fact opens the possibility that a cell with a heritable advantage over the normal cells may gradually produce a clone covering more and more of the basal layer. The advantage in question may consist in a faster rate of division than normal, or a more tenacious hold on the basement membrane; we shall limit consideration to the former situation.

scholarly journals The Actin Gene ACT1 Is Required for Phagocytosis, Motility, and Cell Separation of Tetrahymena thermophila

2006 ◽  
Vol 5 (3) ◽  
pp. 555-567 ◽  
Author(s):  
Norman E. Williams ◽  
Che-Chia Tsao ◽  
Josephine Bowen ◽  
Gery L. Hehman ◽  
Ruth J. Williams ◽  
...  
Keyword(s):  
Cell Separation ◽  
Tetrahymena Thermophila ◽  
Cell Cortex ◽  
Actin Gene ◽  
Wild Type ◽  
Daughter Cells ◽  
Genetic Constructs ◽  
Mutant Cells ◽  
Phagocytic Uptake ◽  
Cell Cycle Length

ABSTRACT A previously identified Tetrahymena thermophila actin gene (C. G. Cupples and R. E. Pearlman, Proc. Natl. Acad. Sci. USA 83:5160-5164, 1986), here called ACT1, was disrupted by insertion of a neo3 cassette. Cells in which all expressed copies of this gene were disrupted exhibited intermittent and extremely slow motility and severely curtailed phagocytic uptake. Transformation of these cells with inducible genetic constructs that contained a normal ACT1 gene restored motility. Use of an epitope-tagged construct permitted visualization of Act1p in the isolated axonemes of these rescued cells. In ACT1Δ mutant cells, ultrastructural abnormalities of outer doublet microtubules were present in some of the axonemes. Nonetheless, these cells were still able to assemble cilia after deciliation. The nearly paralyzed ACT1Δ cells completed cleavage furrowing normally, but the presumptive daughter cells often failed to separate from one another and later became reintegrated. Clonal analysis revealed that the cell cycle length of the ACT1Δ cells was approximately double that of wild-type controls. Clones could nonetheless be maintained for up to 15 successive fissions, suggesting that the ACT1 gene is not essential for cell viability or growth. Examination of the cell cortex with monoclonal antibodies revealed that whereas elongation of ciliary rows and formation of oral structures were normal, the ciliary rows of reintegrated daughter cells became laterally displaced and sometimes rejoined indiscriminately across the former division furrow. We conclude that Act1p is required in Tetrahymena thermophila primarily for normal ciliary motility and for phagocytosis and secondarily for the final separation of daughter cells.

meiotin-1 gene expression in normal anthers and in anthers exhibiting prematurely condensed chromosomes

Genome ◽  
2000 ◽  
Vol 43 (4) ◽  
pp. 604-612 ◽  
Author(s):  
C A Hasenkampf ◽  
A A Taylor ◽  
N U Siddiqui ◽  
C D Riggs
Keyword(s):  
Gene Expression ◽  
Tapetal Cell ◽  
Chromatin Condensation ◽  
Anther Development ◽  
Normal Cells ◽  
Vegetative Tissues ◽  
Tapetal Cells ◽  
Low Levels ◽  
Temporal And Spatial ◽  
Transcriptional Induction

We have cloned and sequenced the promoter of a meiotin-1 gene, and have determined the precise temporal and spatial pattern of meiotin-1 gene expression. The expression of the meiotin-1 gene is controlled in two increments. The meiotin-1 gene is not expressed in any of the vegetative tissues examined. Early in microsporogenesis, low levels of meiotin-1 RNA can be detected. At the onset of meiosis, there is a dramatic increase in meiotin-1 RNA levels in both tapetal and meiotic cells. However, while meiotin-1 RNA is observed in both the nucleus and cytoplasm of meiotic cells, it is found only in the nucleus of the tapetal cells. We have also examined the expression of the meiotin-1 gene in aberrant meiotic nuclei that prematurely condense their chromosomes; these nuclei have reduced levels of the meiotin-1 protein. The aberrant nuclei have only the basal level of meiotin-1 RNA; they do not exhibit the transcriptional induction seen for normal cells at the onset of meiosis. Implications for the function of meiotin-1 in regulating chromatin condensation, and in coordinating meiotic and tapetal cell activities are discussed.Key words: anther development, chromatin, meiosis, meiotin-1, promoter.

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