scholarly journals A New Role for Telomerase in Promoting Meiotic Homolog Pairing Fidelity

2019 ◽  
Author(s):  
Dana L. Smith ◽  
Ashwini Oke ◽  
Michael Pollard ◽  
Carol M. Anderson ◽  
Tangna Zhuge ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Envelope ◽  
High Velocity ◽  
Dramatic Decrease ◽  
Homologous Chromosomes ◽  
Homolog Pairing ◽  
Chromosome Motion

ABSTRACTCytoskeletal forces acting upon telomeres promote active chromosome motion needed to pair homologous chromosomes during meiosis. The necessary components that allow this force to be applied to telomeres is still unclear, as are the roles of this motion and whether motion is needed primarily for increasing collisions of homologous regions, testing homolog pairing fidelity, or some other role. Here, we show a novel role for telomerase, previously known to be responsible for telomeric end replication, in anchoring telomeres to the nuclear envelope (NE) to provide proper transmission of cytoskeletal forces during meiosis. Reduction in telomerase function in Saccharomyces cerevisiae results in a dramatic decrease in the frequency of high velocity “pulls” resulting in earlier homolog synapsis and increased recombination. These observations are consistent with a model in which telomeric cytoskeletal engagement ensures homolog pairing fidelity by pulling apart improperly associated regions whereas general chromosomal motion aids in increasing homologous contacts.

scholarly journals Live imaging and biophysical modeling support a button-based mechanism of somatic homolog pairing in Drosophila

2020 ◽  
Author(s):  
Myron Child ◽  
Jack R. Bateman ◽  
Amir Jahangiri ◽  
Armando Reimer ◽  
Nicholas C. Lammers ◽  
...  
Keyword(s):  
Spatial Configuration ◽  
Live Imaging ◽  
Biophysical Model ◽  
Structural Basis ◽  
Biophysical Modeling ◽  
Homologous Chromosomes ◽  
3D Genome ◽  
Homolog Pairing ◽  
Rna Labeling ◽  
Regulated Gene Expression

AbstractThe spatial configuration of the eukaryotic genome is organized and dynamic, providing the structural basis for regulated gene expression in living cells. In Drosophila melanogaster, 3D genome organization is characterized by somatic homolog pairing, where homologous chromosomes are intimately paired from end to end; however, the process by which homologs identify one another and pair has remained mysterious. A recent model proposed that specifically interacting “buttons” encoded along the lengths of homologous chromosomes drive somatic homolog pairing. Here, we turned this hypothesis into a precise biophysical model to demonstrate that a button-based mechanism can lead to chromosome-wide pairing. We tested our model and constrained its free parameters using live-imaging measurements of chromosomal loci tagged with the MS2 and PP7 nascent RNA labeling systems. Our analysis showed strong agreement between model predictions and experiments in the separation dynamics of tagged homologous loci as they transition from unpaired to paired states, and in the percentage of nuclei that become paired as embryonic development proceeds. In sum, as a result of this dialogue between theory and experiment, our data strongly support a button-based mechanism of somatic homolog pairing in Drosophila and provide a theoretical framework for revealing the molecular identity and regulation of buttons.

Maize meiotic spindles assemble around chromatin and do not require paired chromosomes

1998 ◽  
Vol 111 (23) ◽  
pp. 3507-3515 ◽  
Author(s):  
A. Chan ◽  
W.Z. Cande
Keyword(s):  
Nuclear Envelope ◽  
Higher Plants ◽  
Metaphase Plate ◽  
Meiotic Spindle ◽  
Wild Type ◽  
Homologous Chromosomes ◽  
Nuclear Envelope Breakdown ◽  
Meiotic Spindles ◽  
Meiotic Mutations ◽  
Bipolar Spindles

To understand how the meiotic spindle is formed and maintained in higher plants, we studied the organization of microtubule arrays in wild-type maize meiocytes and three maize meiotic mutants, desynaptic1 (dsy1), desynaptic2 (dsy2), and absence of first division (afd). All three meiotic mutations have abnormal chromosome pairing and produce univalents by diakinesis. Using these three mutants, we investigated how the absence of paired homologous chromosomes affects the assembly and maintenance of the meiotic spindle. Before nuclear envelope breakdown, in wild-type meiocytes, there were no bipolar microtubule arrays. Instead, these structures formed after nuclear envelope breakdown and were associated with the chromosomes. The presence of univalent chromosomes in dsy1, dsy2, and afd meiocytes and of unpaired sister chromatids in the afd meiocytes did not affect the formation of bipolar spindles. However, alignment of chromosomes on the metaphase plate and subsequent anaphase chromosome segregation were perturbed. We propose a model for spindle formation in maize meiocytes in which microtubules initially appear around the chromosomes during prometaphase and then the microtubules self-organize. However, this process does not require paired kinetochores to establish spindle bipolarity.

Assignment of cloned genes to the seven electrophoretically separated Candida albicans chromosomes

1988 ◽  
Vol 8 (11) ◽  
pp. 4721-4726
Author(s):  
B B Magee ◽  
Y Koltin ◽  
J A Gorman ◽  
P T Magee
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Candida Albicans ◽  
Unknown Function ◽  
Gel Electrophoresis ◽  
Homogeneous Field ◽  
Electrophoretic Karyotype ◽  
Chromosome Size ◽  
Homologous Chromosomes ◽  
Orthogonal Field ◽  
Chromosomal Bands

By using orthogonal-field alternating gel electrophoresis (OFAGE), field-inversion gel electrophoresis (FIGE), and contour-clamped homogeneous field gel electrophoresis (CHEF), we have clearly resolved 11 chromosomal bands from various Candida albicans strains. OFAGE resolves the smaller chromosomes better, while FIGE, which under our conditions causes the chromosomes to run in the reverse order of OFAGE, is more effective in separating the larger chromosomes. CHEF separates all chromosomes under some conditions, but these conditions do not often resolve homologs. The strains examined are highly polymorphic for chromosome size. Fourteen cloned Candida genes, isolated on the basis of conferral of new properties to or complementation of auxotrophic deficiencies in Saccharomyces cerevisiae, and three sequences of unknown function have been hybridized to Southern transfers of CHEF, FIGE, and OFAGE gels. Four sets of resolvable bands have been shown to be homologous chromosomes. On the basis of these data, we suggest that C. albicans has seven chromosomes. Genes have been assigned to the seven chromosomes. Two chromosomes identified genetically have been located on the electrophoretic karyotype.

scholarly journals Mutational Analysis of the Structure and Localization of the Nucleolus in the Yeast Saccharomyces cerevisiae

1998 ◽  
Vol 143 (1) ◽  
pp. 23-34 ◽  
Author(s):  
M. Oakes ◽  
J.P. Aris ◽  
J.S. Brockenbrough ◽  
H. Wai ◽  
L. Vu ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Envelope ◽  
Mutational Analysis ◽  
Fusion Gene ◽  
Nuclear Periphery ◽  
Rdna Locus ◽  
Coding Region ◽  
Yeast Saccharomyces Cerevisiae ◽  
Pol I ◽  
Rdna Expression

The nucleolus in Saccharomyces cerevisiae is a crescent-shaped structure that makes extensive contact with the nuclear envelope. In different chromosomal rDNA deletion mutants that we have analyzed, the nucleolus is not organized into a crescent structure, as determined by immunofluorescence microscopy, fluorescence in situ hybridization, and electron microscopy. A strain carrying a plasmid with a single rDNA repeat transcribed by RNA polymerase I (Pol I) contained a fragmented nucleolus distributed throughout the nucleus, primarily localized at the nuclear periphery. A strain carrying a plasmid with the 35S rRNA coding region fused to the GAL7 promoter and transcribed by Pol II contained a rounded nucleolus that often lacked extensive contact with the nuclear envelope. Ultrastructurally distinct domains were observed within the round nucleolus. A similar rounded nucleolar morphology was also observed in strains carrying the Pol I plasmid in combination with mutations that affect Pol I function. In a Pol I–defective mutant strain that carried copies of the GAL7-35S rDNA fusion gene integrated into the chromosomal rDNA locus, the nucleolus exhibited a round morphology, but was more closely associated with the nuclear envelope in the form of a bulge. Thus, both the organization of the rDNA genes and the type of polymerase involved in rDNA expression strongly influence the organization and localization of the nucleolus.

scholarly journals Three-dimensional Ultrastructure of Saccharomyces cerevisiae Meiotic Spindles

2005 ◽  
Vol 16 (3) ◽  
pp. 1178-1188 ◽  
Author(s):  
Mark Winey ◽  
Garry P. Morgan ◽  
Paul D. Straight ◽  
Thomas H. Giddings ◽  
David N. Mastronarde
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Meiotic Chromosome ◽  
Three Dimensional ◽  
Structural Basis ◽  
Mitotic Spindles ◽  
Yeast Saccharomyces Cerevisiae ◽  
Homologous Chromosomes ◽  
Sister Chromatids ◽  
Single Nucleus ◽  
Meiotic Spindles

Meiotic chromosome segregation leads to the production of haploid germ cells. During meiosis I (MI), the paired homologous chromosomes are separated. Meiosis II (MII) segregation leads to the separation of paired sister chromatids. In the budding yeast Saccharomyces cerevisiae, both of these divisions take place in a single nucleus, giving rise to the four-spored ascus. We have modeled the microtubules in 20 MI and 15 MII spindles by using reconstruction from electron micrographs of serially sectioned meiotic cells. Meiotic spindles contain more microtubules than their mitotic counterparts, with the highest number in MI spindles. It is possible to differentiate between MI versus MII spindles based on microtubule numbers and organization. Similar to mitotic spindles, kinetochores in either MI or MII are attached by a single microtubule. The models indicate that the kinetochores of paired homologous chromosomes in MI or sister chromatids in MII are separated at metaphase, similar to mitotic cells. Examination of both MI and MII spindles reveals that anaphase A likely occurs in addition to anaphase B and that these movements are concurrent. This analysis offers a structural basis for considering meiotic segregation in yeast and for the analysis of mutants defective in this process.

scholarly journals Yeast Nuclear Envelope Subdomains with Distinct Abilities to Resist Membrane Expansion

2006 ◽  
Vol 17 (4) ◽  
pp. 1768-1778 ◽  
Author(s):  
Joseph L. Campbell ◽  
Alexander Lorenz ◽  
Keren L. Witkin ◽  
Thomas Hays ◽  
Josef Loidl ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Nuclear Membrane ◽  
Budding Yeast ◽  
Phospholipid Biosynthesis ◽  
Yeast Saccharomyces Cerevisiae ◽  
Nuclear Compartment ◽  
Round Shape ◽  
Nuclear Protrusion

Little is known about what dictates the round shape of the yeast Saccharomyces cerevisiae nucleus. In spo7Δ mutants, the nucleus is misshapen, exhibiting a single protrusion. The Spo7 protein is part of a phosphatase complex that represses phospholipid biosynthesis. Here, we report that the nuclear protrusion of spo7Δ mutants colocalizes with the nucleolus, whereas the nuclear compartment containing the bulk of the DNA is unaffected. Using strains in which the nucleolus is not intimately associated with the nuclear envelope, we show that the single nuclear protrusion of spo7Δ mutants is not a result of nucleolar expansion, but rather a property of the nuclear membrane. We found that in spo7Δ mutants the peripheral endoplasmic reticulum (ER) membrane was also expanded. Because the nuclear membrane and the ER are contiguous, this finding indicates that in spo7Δ mutants all ER membranes, with the exception of the membrane surrounding the bulk of the DNA, undergo expansion. Our results suggest that the nuclear envelope has distinct domains that differ in their ability to resist membrane expansion in response to increased phospholipid biosynthesis. We further propose that in budding yeast there is a mechanism, or structure, that restricts nuclear membrane expansion around the bulk of the DNA.

scholarly journals Shugoshin Promotes Sister Kinetochore Biorientation in Saccharomyces cerevisiae

2008 ◽  
Vol 19 (3) ◽  
pp. 1199-1209 ◽  
Author(s):  
Brendan M. Kiburz ◽  
Angelika Amon ◽  
Adele L. Marston
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Chromosome Segregation ◽  
Minor Role ◽  
Meiotic Cell ◽  
Homologous Chromosomes ◽  
Cell Divisions ◽  
Sister Chromatids ◽  
Sister Kinetochore ◽  
A Minor ◽  
Meiosis I

Chromosome segregation must be executed accurately during both mitotic and meiotic cell divisions. Sgo1 plays a key role in ensuring faithful chromosome segregation in at least two ways. During meiosis this protein regulates the removal of cohesins, the proteins that hold sister chromatids together, from chromosomes. During mitosis, Sgo1 is required for sensing the absence of tension caused by sister kinetochores not being attached to microtubules emanating from opposite poles. Here we describe a differential requirement for Sgo1 in the segregation of homologous chromosomes and sister chromatids. Sgo1 plays only a minor role in segregating homologous chromosomes at meiosis I. In contrast, Sgo1 is important to bias sister kinetochores toward biorientation. We suggest that Sgo1 acts at sister kinetochores to promote their biorientation.

scholarly journals Physical Links Between the Nuclear Envelope Protein Mps3, Three Alternate Replication Factor C Complexes, and a Variant Histone in Saccharomyces cerevisiae

2012 ◽  
Vol 31 (6) ◽  
pp. 917-924 ◽  
Author(s):  
Jared Haas ◽  
Amanda Lemoncelli ◽  
Christina Morozov ◽  
Karl Franke ◽  
John Dominder ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Envelope ◽  
Envelope Protein ◽  
Replication Factor C ◽  
Replication Factor ◽  
Factor C

scholarly journals RAD10, an excision repair gene of Saccharomyces cerevisiae, is involved in the RAD1 pathway of mitotic recombination.

1990 ◽  
Vol 10 (6) ◽  
pp. 2485-2491 ◽  
Author(s):  
R H Schiestl ◽  
S Prakash
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Meiotic Recombination ◽  
Excision Repair ◽  
Mitotic Recombination ◽  
The Other ◽  
Gene Products ◽  
Repair Gene ◽  
Homologous Chromosomes ◽  
Intrachromosomal Recombination ◽  
Recombination Pathway

The RAD10 gene of Saccharomyces cerevisiae is required for the incision step of excision repair of UV-damaged DNA. We show that the RAD10 gene is also required for mitotic recombination. The rad10 delta mutation lowered the rate of intrachromosomal recombination of a his3 duplication in which one his3 allele has a deletion at the 3' end and the other his3 allele has a deletion at the 5' end (his3 delta 3' his3 delta 5'). The rate of formation of HIS3+ recombinants in the rad10 delta mutant was not affected by the rad1 delta mutation but decreased synergistically in the presence of the rad10 delta mutation in combination with the rad52 delta mutation. These observations indicate that the RAD1 and RAD10 genes function together in a mitotic recombination pathway that is distinct from the RAD52 recombination pathway. The rad10 delta mutation also lowered the efficiency of integration of linear DNA molecules and circular plasmids into homologous genomic sequences. We suggest that the RAD1 and RAD10 gene products act in recombination after the formation of the recombinogenic substrate. The rad1 delta and rad10 delta mutations did not affect meiotic intrachromosomal recombination of the his3 delta 3' his3 delta 5' duplication or mitotic and meiotic recombination of ade2 heteroalleles located on homologous chromosomes.

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