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https://www.readbyqxmd.com/read/27858158/structure-of-centromere-chromatin-from-nucleosome-to-chromosomal-architecture
#1
REVIEW
Thomas Schalch, Florian A Steiner
The centromere is essential for the segregation of chromosomes, as it serves as attachment site for microtubules to mediate chromosome segregation during mitosis and meiosis. In most organisms, the centromere is restricted to one chromosomal region that appears as primary constriction on the condensed chromosome and is partitioned into two chromatin domains: The centromere core is characterized by the centromere-specific histone H3 variant CENP-A (also called cenH3) and is required for specifying the centromere and for building the kinetochore complex during mitosis...
November 17, 2016: Chromosoma
https://www.readbyqxmd.com/read/27837282/the-chromosomal-basis-of-meiotic-acentrosomal-spindle-assembly-and-function-in-oocytes
#2
REVIEW
Sarah J Radford, Alexandra L Nguyen, Karen Schindler, Kim S McKim
Several aspects of meiosis are impacted by the absence of centrosomes in oocytes. Here, we review four aspects of meiosis I that are significantly affected by the absence of centrosomes in oocyte spindles. One, microtubules tend to assemble around the chromosomes. Two, the organization of these microtubules into a bipolar spindle is directed by the chromosomes. Three, chromosome bi-orientation and attachment to microtubules from the correct pole require modification of the mechanisms used in mitotic cells. Four, chromosome movement to the poles at anaphase cannot rely on polar anchoring of spindle microtubules by centrosomes...
November 11, 2016: Chromosoma
https://www.readbyqxmd.com/read/27826839/structure-and-mechanism-of-plant-dna-methyltransferases
#3
Jiamu Du
DNA methylation is an important epigenetic mark that functions in eukaryotes from fungi to animals and plants, where it plays a crucial role in the regulation of epigenetic silencing. Once the methylation mark is established by the de novo DNA methyltransferase (MTase), it requires specific regulatory mechanisms to maintain the methylation state during chromatin replication, both during meiosis and mitosis. Plants have distinct DNA methylation patterns that are both established and maintained by unique DNA MTases and are regulated by plant-specific pathways...
2016: Advances in Experimental Medicine and Biology
https://www.readbyqxmd.com/read/27826797/the-cohesion-stabilizer-sororin-favors-dna-repair-and-chromosome-segregation-during-mouse-oocyte-meiosis
#4
Chun-Jie Huang, Yi-Feng Yuan, Di Wu, Faheem Ahmed Khan, Xiao-Fei Jiao, Li-Jun Huo
Maintenance and timely termination of cohesion on chromosomes ensures accurate chromosome segregation to guard against aneuploidy in mammalian oocytes and subsequent chromosomally abnormal pregnancies. Sororin, a cohesion stabilizer whose relevance in antagonizing the anti-cohesive property of Wings-apart like protein (Wapl), has been characterized in mitosis; however, the role of Sororin remains unclear during mammalian oocyte meiosis. Here, we show that Sororin is required for DNA damage repair and cohesion maintenance on chromosomes, and consequently, for mouse oocyte meiotic program...
November 8, 2016: In Vitro Cellular & Developmental Biology. Animal
https://www.readbyqxmd.com/read/27818689/epigenetic-remodeling-in-male-germline-development
#5
REVIEW
Na Li, Qiaoyan Shen, Jinlian Hua
In mammals, germ cells guarantee the inheritance of genetic and epigenetic information across generations and are the origin of a new organism. During embryo development, the blastocyst is formed in the early stage, is comprised of an inner cell mass which is pluripotent, and could give rise to the embryonic stem cells (ESCs). The inner cell mass undergoes demethylation processes and will reestablish a methylated state that is similar to that of somatic cells later in epiblast stage. Primordial germ cells (PGCs) will be formed very soon and accompanied by the process of genome-wide demethylation...
2016: Stem Cells International
https://www.readbyqxmd.com/read/27816818/the-spindle-checkpoint-in-plants-a-green-variation-over-a-conserved-theme
#6
REVIEW
Shinichiro Komaki, Arp Schnittger
The spindle checkpoint, also called spindle assembly checkpoint (SAC), is a crucial control instance in animals and yeast that surveys the correct attachment of chromosomes to the spindle assuring their equal distribution in mitosis and meiosis. The presence of homologs of all core SAC components in plants indicates that these regulators have an ancient function. However, the fact that mutants of SAC components in plants are usually fully viable together with the observation that plants can be readily made polyploid raises the question whether plants have an efficient SAC...
October 27, 2016: Current Opinion in Plant Biology
https://www.readbyqxmd.com/read/27803161/molecular-basis-for-cohesin-acetylation-by-establishment-of-sister-chromatid-cohesion-n-acetyltransferase-esco1
#7
Yadilette Rivera-Colón, Andrew Maguire, Glen P Liszczak, Adam S Olia, Ronen Marmorstein
Protein acetylation is a prevalent posttranslational modification that is regulated by diverse acetyltransferase enzymes. While histone acetyltransferases (HATs) have been well characterized both structurally and mechanistically, far less is known about non-histone acetyltransferase enzymes. The human ESCO1 and ESCO2 paralogs acetylate the cohesin complex subunit SMC3 to regulate the separation of sister chromatids during mitosis and meiosis. Missense mutations within the acetyltransferase domain of these proteins correlate with diseases, including endometrial cancers and Roberts Syndrome...
November 1, 2016: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/27797084/a-protocol-for-measuring-mitotic-chromosome-condensation-quantitatively-in-fission-yeast-cells
#8
Christoph Schiklenk, Boryana Petrova, Christian H Haering
Even though the formation of compact cylindrical chromosomes early during mitosis or meiosis is a prerequisite for the successful segregation of eukaryotic genomes, little is known about the molecular basis of this chromosome condensation process. Here, we describe in detail the protocol for a quantitative chromosome condensation assay in fission yeast cells, which is based on precise time-resolved measurements of the distances between two fluorescently labeled positions on the same chromosome. In combination with an automated computational analysis pipeline, this assay enables the study of various candidate proteins for their roles in regulating genome topology during cell divisions...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/27794100/starch-turnover-and-metabolism-during-flower-and-early-embryo-development
#9
Afif Hedhly, Hannes Vogler, Marc W Schmid, Diana Pazmino, Valeria Gagliardini, Diana Santelia, Ueli Grossniklaus
The accumulation of starch within photosynthetic tissues and within dedicated storage organs has been characterized extensively in many species, and a function in buffering carbon availability or in fueling later growth phases, respectively, has been proposed. However, developmentally regulated starch turnover within heterotrophic tissues other than dedicated storage organs is poorly characterized, and its function is not well understood. Here, we report on the characterization of starch turnover during flower, early embryo, and silique development in Arabidopsis (Arabidopsis thaliana) using a combined clearing-staining technique on whole-mount tissue...
December 2016: Plant Physiology
https://www.readbyqxmd.com/read/27767093/turning-rice-meiosis-into-mitosis
#10
Delphine Mieulet, Sylvie Jolivet, Maud Rivard, Laurence Cromer, Aurore Vernet, Pauline Mayonove, Lucie Pereira, Gaëtan Droc, Brigitte Courtois, Emmanuel Guiderdoni, Raphael Mercier
Introduction of clonal reproduction through seeds (apomixis) in crops has the potential to revolutionize agriculture by allowing self-propagation of any elite variety, in particular F1 hybrids. In the sexual model plant Arabidopsis thaliana synthetic clonal reproduction through seeds can be artificially implemented by (i) combining three mutations to turn meiosis into mitosis (MiMe) and (ii) crossing the obtained clonal gametes with a line expressing modified CENH3 and whose genome is eliminated in the zygote...
October 21, 2016: Cell Research
https://www.readbyqxmd.com/read/27759153/the-master-greatwall-kinase-a-critical-regulator-of-mitosis-and-meiosis
#11
Suzanne Vigneron, Perle Robert, Khaled Hached, Lena Sundermann, Sophie Charrasse, Jean-Claude Labbé, Anna Castro, Thierry Lorca
Entry into mitosis requires the coordinated activation of various protein kinases and phosphatases that together activate sequential signaling pathways allowing entry, progression and exit of mitosis. The limiting step is thought to be the activation of the mitotic Cdk1-cyclin B kinase. However, this model has recently evolved with new data showing that in addition to the Cdk1-cyclin B complex, Greatwall (Gwl) kinase is also required to enter into and maintain mitosis. This new concept proposes that entry into mitosis is now based on the combined activation of both kinases Cdk1-cyclin B and Gwl, the former promoting massive phosphorylation of mitotic substrates and the latter inhibiting PP2A-B55 phosphatase responsible for dephosphorylation of these substrates...
2016: International Journal of Developmental Biology
https://www.readbyqxmd.com/read/27757782/identification-of-candidate-biomarkers-and-analysis-of-prognostic-values-in-ovarian-cancer-by-integrated-bioinformatics-analysis
#12
Zhanzhan Xu, Yu Zhou, Yexuan Cao, Thi Lan Anh Dinh, Jing Wan, Min Zhao
Ovarian cancer is the first leading cause of mortality in gynecological malignancies. To identify key genes and microRNAs in ovarian cancer, mRNA microarray dataset GSE36668, GSE18520, GSE14407 and microRNA dataset GSE47841 were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) and microRNAs (DEMs) were obtained using GEO2R. Functional and pathway enrichment analysis were performed for DEGs using DAVID database. Protein-protein interaction (PPI) network was established by STRING and visualized by Cytoscape...
November 2016: Medical Oncology
https://www.readbyqxmd.com/read/27729423/maternal-memi-promotes-female-meiosis-ii-in-response-to-fertilization-in-caenorhabditis-elegans
#13
Maryam Ataeian, Justus Tegha-Dunghu, Donna G Curtis, Ellen M E Sykes, Ashkan Nozohourmehrabad, Megha Bajaj, Karen Cheung, Martin Srayko
In most animals, female meiosis completes only after fertilization. Sperm entry has been implicated in providing a signal for the initiation of the final meiotic processes, however, a maternal component required for this process has not been previously identified. We report the characterization of a novel family of three highly similar paralogs (memi-1, memi-2, memi-3) that encode oocyte-specific proteins. A hypermorphic mutation memi-1(sb41) results in failure to exit female meiosis II properly, however, loss of all three paralogs results in a "skipped meiosis II" phenotype...
October 11, 2016: Genetics
https://www.readbyqxmd.com/read/27715428/highlight-on-the-dynamic-organisation-of-the-nucleus
#14
Stephen D Thorpe, Myriam Charpentier
The last decade has seen rapid advances in our understanding of the proteins of the nuclear envelope, which have multiple roles including positioning the nucleus, maintaining its structural organisation, and in events ranging from mitosis and meiosis to chromatin positioning and gene expression. Diverse new and stimulating results relating to nuclear organisation and genome function from across kingdoms were presented in a session stream entitled "Dynamic Organisation of the Nucleus" at this year's Society of Experimental Biology (SEB) meeting in Brighton, UK (July 2016)...
October 7, 2016: Nucleus
https://www.readbyqxmd.com/read/27707787/the-identification-of-a-novel-mutant-allele-of-topoisomerase-ii-in-caenorhabditis-elegans-reveals-a-unique-role-in-chromosome-segregation-during-spermatogenesis
#15
Aimee Jaramillo-Lambert, Amy S Fabritius, Tyler J Hansen, Harold E Smith, Andy Golden
Topoisomerase II alleviates DNA entanglements that are generated during mitotic DNA replication, transcription, and sister chromatid separation. In contrast to mitosis, meiosis has two rounds of chromosome segregation following one round of DNA replication. In meiosis II, sister chromatids segregate from each other similar to mitosis. Meiosis I, on the other hand, segregates homologs, which requires pairing, synapsis, and recombination. The exact role that topoisomerase II plays during meiosis is unknown. In a screen re-examining Caenorhabditis elegant legacy mutants isolated thirty years ago, we identified a novel allele of the gene encoding topoisomerase II, top-2(it7) In this study, we demonstrate that top-2(it7) males produce dead embryos, even when fertilizing wild-type oocytes...
October 5, 2016: Genetics
https://www.readbyqxmd.com/read/27693251/inhibition-of-cdk7-bypasses-spindle-assembly-checkpoint-via-premature-cyclin-b-degradation-during-oocyte-meiosis
#16
HaiYang Wang, Yu-Jin Jo, Tian-Yi Sun, Suk Namgoong, Xiang-Shun Cui, Jeong Su Oh, Nam-Hyung Kim
To ensure accurate chromosome segregation, the spindle assembly checkpoint (SAC) delays anaphase onset by preventing the premature activation of anaphase-promoting complex/cyclosome (APC/C) until all kinetochores are attached to the spindle. Although an escape from mitosis in the presence of unsatisfied SAC has been shown in several cancer cells, it has not been reported in oocyte meiosis. Here, we show that CDK7 activity is required to prevent a bypass of SAC during meiosis I in mouse oocytes. Inhibition of CDK7 using THZ1 accelerated the first meiosis, leading to chromosome misalignment, lag of chromosomes during chromosome segregation, and a high incidence of aneuploidy...
December 2016: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/27678504/cullin9-protects-mouse-eggs-from-aneuploidy-by-controlling-microtubule-dynamics-via-survivin
#17
Xiaoxin Dai, Mianqun Zhang, Yajuan Lu, Yilong Miao, Changyin Zhou, Bo Xiong
The Cullin9 gene encodes a putative E3 ligase that serves a wide variety of biological functions in mitosis, whereas its roles in meiosis have not yet clearly defined. Here, we report that Cullin9 accumulates on the spindle apparatus and colocalizes with the microtubule fibers during mouse oocyte meiotic maturation. Depletion of Cullin9 by morpholino microinjection results in a remarkably higher rate of disorganized spindles and misaligned chromosomes in oocytes, which is coupled with the impaired kinetochore-microtubule attachments...
December 2016: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/27677401/the-role-of-rad51-in-safeguarding-mitochondrial-activity-during-the-meiotic-cell-cycle-in-mammalian-oocytes
#18
Kyeoung-Hwa Kim, Ji-Hoon Park, Eun-Young Kim, Jung-Jae Ko, Kyung-Soon Park, Kyung-Ah Lee
Rad51 is a conserved eukaryotic protein that mediates the homologous recombination repair of DNA double-strand breaks that occur during mitosis and meiosis. In addition, Rad51 promotes mitochondrial DNA synthesis when replication stress is increased. Rad51 also regulates cell cycle progression by preserving the G2/M transition in embryonic stem cells. In this study, we report a novel function of Rad51 in regulating mitochondrial activity during in vitro maturation of mouse oocytes. Suppression of Rad51 by injection of Rad51 dsRNA into germinal vesicle-stage oocytes resulted in arrest of meiosis in metaphase I...
September 28, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27672111/a-simplified-strategy-for-introducing-genetic-variants-into-drosophila-compound-autosome-stocks
#19
William D Gilliland, Dennis P May, Eileen M Colwell, James A Kennison
Drosophila stocks bearing compound chromosomes, single molecules of DNA that carry the genomic complement of two chromosomes, are useful tools for studying meiosis and mitosis. However, these stocks cannot easily be crossed to stocks with regular chromosomes, due to the lethality of the resulting whole-chromosome aneuploidy. This prevents the examination of interesting genetic variants in a compound chromosome background. Methods to circumvent this difficulty have included the use of triploid females or nondisjunction (caused by either cold-induced microtubule depolymerization or meiotic mutants...
September 26, 2016: G3: Genes—Genomes—Genetics
https://www.readbyqxmd.com/read/27669152/functional-snps-of-incenp-affect-semen-quality-by-alternative-splicing-mode-and-binding-affinity-with-the-target-bta-mir-378-in-chinese-holstein-bulls
#20
Juan Liu, Yan Sun, Chunhong Yang, Yan Zhang, Qiang Jiang, Jinming Huang, Zhihua Ju, Xiuge Wang, Jifeng Zhong, Changfa Wang
Inner centromere protein (INCENP) plays an important role in mitosis and meiosis as the main member of chromosomal passenger protein complex (CPC). To investigate the functional markers of the INCENP gene associated with semen quality, the single nucleotide polymorphisms (SNPs) g.19970 A>G and g.34078 T>G were identified and analyzed. The new splice variant INCENP-TV is characterized by the deletion of exon 12. The g.19970 A>G in the exonic splicing enhancer (ESE) motif region results in an aberrant splice variant by constructing two minigene expression vectors using the pSPL3 exon capturing vector and transfecting vectors into MLTC-1 cells...
2016: PloS One
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