Crosstalk of the Mitotic Spindle Assembly Checkpoint with P53 to Prevent Polyploidy
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Glossary - Cellbiology
1 Glossary - Cellbiology Blotting: (Blot Analysis) Widely used biochemical technique for detecting the presence of specific macromolecules (proteins, mRNAs, or DNA sequences) in a mixture. A sample first is separated on an agarose or polyacrylamide gel usually under denaturing conditions; the separated components are transferred (blotting) to a nitrocellulose sheet, which is exposed to a radiolabeled molecule that specifically binds to the macromolecule of interest, and then subjected to autoradiography. Northern B.: mRNAs are detected with a complementary DNA; Southern B.: DNA restriction fragments are detected with complementary nucleotide sequences; Western B.: Proteins are detected by specific antibodies. Cell: The fundamental unit of living organisms. Cells are bounded by a lipid-containing plasma membrane, containing the central nucleus, and the cytoplasm. Cells are generally capable of independent reproduction. More complex cells like Eukaryotes have various compartments (organelles) where special tasks essential for the survival of the cell take place. Cytoplasm: Viscous contents of a cell that are contained within the plasma membrane but, in eukaryotic cells, outside the nucleus. The part of the cytoplasm not contained in any organelle is called the Cytosol. Cytoskeleton: (Gk. ) Three dimensional network of fibrous elements, allowing precisely regulated movements of cell parts, transport organelles, and help to maintain a cell’s shape. • Actin filament: (Microfilaments) Ubiquitous eukaryotic cytoskeletal proteins (one end is attached to the cell-cortex) of two “twisted“ actin monomers; are important in the structural support and movement of cells. Each actin filament (F-actin) consists of two strands of globular subunits (G-Actin) wrapped around each other to form a polarized unit (high ionic cytoplasm lead to the formation of AF, whereas low ion-concentration disassembles AF). -
Meiotic Prophase Abnormalities and Metaphase Cell Death in MLH1-Deficient Mouse Spermatocytes: Insights Into Regulation of Spermatogenic Progress
Developmental Biology 249, 85–95 (2002) doi:10.1006/dbio.2002.0708 Meiotic Prophase Abnormalities and Metaphase Cell Death in MLH1-Deficient Mouse Spermatocytes: Insights into Regulation of Spermatogenic Progress Shannon Eaker,1 John Cobb,2 April Pyle, and Mary Ann Handel3 Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996 The MLH1 protein is required for normal meiosis in mice and its absence leads to failure in maintenance of pairing between bivalent chromosomes, abnormal meiotic division, and ensuing sterility in both sexes. In this study, we investigated whether failure to develop foci of MLH1 protein on chromosomes in prophase would lead to elimination of prophase spermatocytes, and, if not, whether univalent chromosomes could align normally on the meiotic spindle and whether metaphase spermatocytes would be delayed and/or eliminated. In spite of the absence of MLH1 foci, no apoptosis of spermatocytes in prophase was detected. In fact, chromosomes of pachytene spermatocytes from Mlh1؊/؊ mice were competent to condense metaphase chromosomes, both in vivo and in vitro. Most condensed chromosomes were univalents with spatially distinct FISH signals. Typical metaphase events, such as synaptonemal complex breakdown and the phosphorylation of Ser10 on histone H3, occurred in Mlh1؊/؊ spermatocytes, suggesting that there is no inhibition of onset of meiotic metaphase in the face of massive chromosomal abnormalities. However, the condensed univalent chromosomes did not align correctly onto the spindle apparatus in the majority of Mlh1؊/؊ spermatocytes. Most meiotic metaphase spermatocytes were characterized with bipolar spindles, but chromosomes radiated away from the microtubule-organizing centers in a prometaphase-like pattern rather than achieving a bipolar orientation. -
The Role of Model Organisms in the History of Mitosis Research
Downloaded from http://cshperspectives.cshlp.org/ on September 30, 2021 - Published by Cold Spring Harbor Laboratory Press The Role of Model Organisms in the History of Mitosis Research Mitsuhiro Yanagida Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan Correspondence: [email protected] Mitosis is a cell-cycle stage during which condensed chromosomes migrate to the middle of the cell and segregate into two daughter nuclei before cytokinesis (cell division) with the aid of a dynamic mitotic spindle. The history of mitosis research is quite long, commencing well before the discovery of DNA as the repository of genetic information. However, great and rapid progress has been made since the introduction of recombinant DNA technology and discovery of universal cell-cycle control. A large number of conserved eukaryotic genes required for the progression from early to late mitotic stages have been discovered, confirm- ing that DNA replication and mitosis are the two main events in the cell-division cycle. In this article, a historical overview of mitosis is given, emphasizing the importance of diverse model organisms that have been used to solve fundamental questions about mitosis. Onko Chisin—An attempt to discover new truths by checkpoint [SAC]), then metaphase (in which studying the past through scrutiny of the old. the chromosomes are aligned in the middle of cell), anaphase A (in which identical sister chro- matids comprising individual chromosomes LARGE SALAMANDER CHROMOSOMES separate and move toward opposite poles of ENABLED THE FIRST DESCRIPTION the cell), anaphase B (in which the spindle elon- OF MITOSIS gates as the chromosomes approach the poles), itosis means “thread” in Greek. -
Mitosis Vs. Meiosis
Mitosis vs. Meiosis In order for organisms to continue growing and/or replace cells that are dead or beyond repair, cells must replicate, or make identical copies of themselves. In order to do this and maintain the proper number of chromosomes, the cells of eukaryotes must undergo mitosis to divide up their DNA. The dividing of the DNA ensures that both the “old” cell (parent cell) and the “new” cells (daughter cells) have the same genetic makeup and both will be diploid, or containing the same number of chromosomes as the parent cell. For reproduction of an organism to occur, the original parent cell will undergo Meiosis to create 4 new daughter cells with a slightly different genetic makeup in order to ensure genetic diversity when fertilization occurs. The four daughter cells will be haploid, or containing half the number of chromosomes as the parent cell. The difference between the two processes is that mitosis occurs in non-reproductive cells, or somatic cells, and meiosis occurs in the cells that participate in sexual reproduction, or germ cells. The Somatic Cell Cycle (Mitosis) The somatic cell cycle consists of 3 phases: interphase, m phase, and cytokinesis. 1. Interphase: Interphase is considered the non-dividing phase of the cell cycle. It is not a part of the actual process of mitosis, but it readies the cell for mitosis. It is made up of 3 sub-phases: • G1 Phase: In G1, the cell is growing. In most organisms, the majority of the cell’s life span is spent in G1. • S Phase: In each human somatic cell, there are 23 pairs of chromosomes; one chromosome comes from the mother and one comes from the father. -
Polo-Like Kinase 1: Target and Regulator of Anaphase-Promoting Complex/Cyclosome–Dependent Proteolysis Frank Eckerdt1 and Klaus Strebhardt2
Review Polo-Like Kinase 1: Target and Regulator of Anaphase-Promoting Complex/Cyclosome–Dependent Proteolysis Frank Eckerdt1 and Klaus Strebhardt2 1Department of Pharmacology, University of Colorado School of Medicine, Denver, Colorado and 2Department of Gynecology and Obstetrics, Medical School, J.W. Goethe-University, Frankfurt, Germany Abstract to the regulation of the APC/C, an E3 ubiquitin ligase that is Polo-like kinase 1 (Plk1) is a key regulator of progression responsible for the timely destruction of various mitotic proteins, through mitosis. Although Plk1 seems to be dispensable for thereby regulating chromosome segregation, exit from mitosis, entry into mitosis, its role in spindle formation and exit from and a stable subsequent G1 phase (3).The APC/C is first activated by the ancillary protein Cdc20, targeting proteins containing a mitosis is crucial. Recent evidence suggests that a major role Cdc20 of Plk1 in exit from mitosis is the regulation of inhibitors of destruction box (D box), like securin.Once APC/C has the anaphase-promoting complex/cyclosome (APC/C), such as initiated mitotic exit, Cdc20 itself is degraded and is replaced by Cdh1, allowing the degradation of a wider spectrum of substrates. the early mitotic inhibitor 1 (Emi1) and spindle checkpoint Cdh1 proteins. Thus, Plk1 and the APC/C control mitotic regulators The APC/C complex targets not only D box–containing proteins but also proteins exhibiting a KEN box and/or an A box by both phosphorylation and targeted ubiquitylation to Cdh1 ensure the fidelity of chromosome separation at the meta- (e.g., cyclin B1 and Aurora A). Plk1 itself is an APC/C target. -
Cell Division- Ch 5
Cell Division- Mitosis and Meiosis When do cells divide? Cell size . One of most important factors affecting size of the cell is size of cell membrane . Cell must remain relatively small to survive (why?) – Cell membrane has to be big enough to take in nutrients and eliminate wastes – As cells get bigger, the volume increases faster than the surface area – Small cells have a larger surface area to volume ratio than larger cells to help with nutrient intake and waste elimination . When a cell reaches its max size, the nucleus starts cell division: called MITOSIS or MEIOSIS Mitosis . General Information – Occurs in somatic (body) cells ONLY!! – Nickname: called “normal” cell division – Produces somatic cells only . Background Info – Starts with somatic cell in DIPLOID (2n) state . Cell contains homologous chromosomes- chromosomes that control the same traits but not necessarily in the same way . 1 set from mom and 1 set from dad – Ends in diploid (2n) state as SOMATIC cells – Goes through one set of divisions – Start with 1 cell and end with 2 cells Mitosis (cont.) . Accounts for three essential life processes – Growth . Result of cell producing new cells . Develop specialized shapes/functions in a process called differentiation . Rate of cell division controlled by GH (Growth Hormone) which is produced in the pituitary gland . Ex. Nerve cell, intestinal cell, etc. – Repair . Cell regenerates at the site of injury . Ex. Skin (replaced every 28 days), blood vessels, bone Mitosis (cont.) – Reproduction . Asexual – Offspring produced by only one parent – Produce offspring that are genetically identical – MITOSIS – Ex. Bacteria, fungi, certain plants and animals . -
The Emerging Role of Ncrnas and RNA-Binding Proteins in Mitotic Apparatus Formation
non-coding RNA Review The Emerging Role of ncRNAs and RNA-Binding Proteins in Mitotic Apparatus Formation Kei K. Ito, Koki Watanabe and Daiju Kitagawa * Department of Physiological Chemistry, Graduate School of Pharmaceutical Science, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan; [email protected] (K.K.I.); [email protected] (K.W.) * Correspondence: [email protected] Received: 11 November 2019; Accepted: 13 March 2020; Published: 20 March 2020 Abstract: Mounting experimental evidence shows that non-coding RNAs (ncRNAs) serve a wide variety of biological functions. Recent studies suggest that a part of ncRNAs are critically important for supporting the structure of subcellular architectures. Here, we summarize the current literature demonstrating the role of ncRNAs and RNA-binding proteins in regulating the assembly of mitotic apparatus, especially focusing on centrosomes, kinetochores, and mitotic spindles. Keywords: ncRNA; centrosome; kinetochore; mitotic spindle 1. Introduction Non-coding RNAs (ncRNAs) are defined as a class of RNA molecules that are transcribed from genomic DNA, but not translated into proteins. They are mainly classified into the following two categories according to their length—small RNA (<200 nt) and long non-coding RNA (lncRNA) (>200 nt). Small RNAs include traditional RNA molecules, such as transfer RNA (tRNA), small nuclear RNA (snRNA), small nucleolar RNA (snoRNA), PIWI-interacting RNA (piRNA), and micro RNA (miRNA), and they have been studied extensively [1]. Research on lncRNA is behind that on small RNA despite that recent transcriptome analysis has revealed that more than 120,000 lncRNAs are generated from the human genome [2–4]. -
The Cell Cycle & Mitosis
The Cell Cycle & Mitosis Cell Growth The Cell Cycle is G1 phase ___________________________________ _______________________________ During the Cell Cycle, a cell ___________________________________ ___________________________________ Anaphase Cell Division ___________________________________ Mitosis M phase M ___________________________________ S phase replication DNA Interphase Interphase is ___________________________ ___________________________________ G2 phase Interphase is divided into three phases: ___, ___, & ___ G1 Phase S Phase G2 Phase The G1 phase is a period of The S phase replicates During the G2 phase, many of activity in which cells _______ ________________and the organelles and molecules ____________________ synthesizes _______ molecules. required for ____________ __________ Cells will When DNA replication is ___________________ _______________ and completed, _____________ When G2 is completed, the cell is synthesize new ___________ ____________________ ready to enter the ____________________ ____________________ ____________________ ____________________ ____________________ Mitosis are divided into four phases: _____________, ______________, _____________, & _____________ Below are cells in two different phases of the cell cycle, fill in the blanks using the word bank: Chromatin Nuclear Envelope Chromosome Sister Chromatids Nucleolus Spinder Fiber Centrosome Centrioles 5.._________ 1.__________ v 6..__________ 2.__________ 7.__________ 3.__________ 8..__________ 4.__________ v The Cell Cycle & Mitosis Microscope Lab: -
List, Describe, Diagram, and Identify the Stages of Meiosis
Meiosis and Sexual Life Cycles Objective # 1 In this topic we will examine a second type of cell division used by eukaryotic List, describe, diagram, and cells: meiosis. identify the stages of meiosis. In addition, we will see how the 2 types of eukaryotic cell division, mitosis and meiosis, are involved in transmitting genetic information from one generation to the next during eukaryotic life cycles. 1 2 Objective 1 Objective 1 Overview of meiosis in a cell where 2N = 6 Only diploid cells can divide by meiosis. We will examine the stages of meiosis in DNA duplication a diploid cell where 2N = 6 during interphase Meiosis involves 2 consecutive cell divisions. Since the DNA is duplicated Meiosis II only prior to the first division, the final result is 4 haploid cells: Meiosis I 3 After meiosis I the cells are haploid. 4 Objective 1, Stages of Meiosis Objective 1, Stages of Meiosis Prophase I: ¾ Chromosomes condense. Because of replication during interphase, each chromosome consists of 2 sister chromatids joined by a centromere. ¾ Synapsis – the 2 members of each homologous pair of chromosomes line up side-by-side to form a tetrad consisting of 4 chromatids: 5 6 1 Objective 1, Stages of Meiosis Objective 1, Stages of Meiosis Prophase I: ¾ During synapsis, sometimes there is an exchange of homologous parts between non-sister chromatids. This exchange is called crossing over. 7 8 Objective 1, Stages of Meiosis Objective 1, Stages of Meiosis (2N=6) Prophase I: ¾ the spindle apparatus begins to form. ¾ the nuclear membrane breaks down: Prophase I 9 10 Objective 1, Stages of Meiosis Objective 1, 4 Possible Metaphase I Arrangements: Metaphase I: ¾ chromosomes line up along the equatorial plate in pairs, i.e. -
Opium Alkaloid Noscapine Is an Antitumor Agent That Arrests Metaphase and Induces Apoptosis in Dividing Cells
Proc. Natl. Acad. Sci. USA Vol. 95, pp. 1601–1606, February 1998 Cell Biology Opium alkaloid noscapine is an antitumor agent that arrests metaphase and induces apoptosis in dividing cells KEQIANG YE*†,YONG KE‡,NAGALAKSHMI KESHAVA§,JOHN SHANKS†,JUDITH A. KAPP‡,RAJESHWAR R. TEKMAL§, i JOHN PETROS¶, AND HARISH C. JOSHI*† *Graduate Program in Biochemistry and Molecular Biology, Departments of †Anatomy and Cell Biology, ‡Pathology, §Gynecology–Obstetrics, and ¶Urology, Emory University School of Medicine, Atlanta, GA 30322 Edited by Thomas D. Pollard, Salk Institute for Biological Studies, La Jolla, CA, and approved December 17, 1997 (received for review July 17, 1997) ABSTRACT An alkaloid from opium, noscapine, is used (2,3,4-trimethoxyphenyl)-2,4,6-cycloheptatrien-1-one], TCB as an antitussive drug and has low toxicity in humans and (2,3,4-trimethoxy-49-carbomethoxy-1,19-biphenyl), and TKB mice. We show that noscapine binds stoichiometrically to (2,3,4-trimethoxy-49-acetyl-1,19-biphenyl), and vinca alkaloids. tubulin, alters its conformation, affects microtubule assembly, Taxol and its analogs represent the compounds that promote and arrests mammalian cells in mitosis. Furthermore, the assembly of microtubules. It is now clear that although all noscapine causes apoptosis in many cell types and has potent of these microtubule drugs prevent cell division, only a select antitumor activity against solid murine lymphoid tumors few have been useful clinically. In addition, there are differ- (even when the drug was administered orally) and against ences regarding the toxicity and the efficacy of these drugs for human breast and bladder tumors implanted in nude mice. -
Lte1 Promotes Mitotic Exit by Controlling the Localization of the Spindle Position Checkpoint Kinase Kin4
Lte1 promotes mitotic exit by controlling the localization of the spindle position checkpoint kinase Kin4 Jill E. Falk1, Leon Y. Chan1,2, and Angelika Amon3 David H. Koch Institute for Integrative Cancer Research and Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139 This contribution is part of the special series of Inaugural Articles by members of the National Academy of Sciences elected in 2010. Contributed by Angelika Amon, May 17, 2011 (sent for review April 27, 2011) For a daughter cell to receive a complete genomic complement, it is The work by Adames et al. (13) proposed a model in which essential that the mitotic spindle be positioned accurately within the interactions between microtubules and the bud neck inhibit the cell. In budding yeast, a signaling system known as the spindle MEN, but how this could lead to Kin4 activation, if indeed Kin4 is position checkpoint (SPOC) monitors spindle position and regulates activated by spindle misposition, is not known. We previously the activity of the mitotic exit network (MEN), a GTPase signaling proposed a model termed the zone model, which posits that the pathway that promotes exit from mitosis. The protein kinase Kin4 budding yeast cell is divided into a MEN inhibitory zone in the is a central component of the spindle position checkpoint. Kin4 mother cell and a MEN activating zone in the daughter cell and primarily localizes to the mother cell and associates with spindle that a sensor, the GTPase Tem1, moves between them. Tem1 as well as most other components of the MEN reside at pole bodies (SPBs) located in the mother cell to inhibit MEN spindle pole bodies (SPBs; yeast centrosomes). -
Cell Life Cycle and Reproduction the Cell Cycle (Cell-Division Cycle), Is a Series of Events That Take Place in a Cell Leading to Its Division and Duplication
Cell Life Cycle and Reproduction The cell cycle (cell-division cycle), is a series of events that take place in a cell leading to its division and duplication. The main phases of the cell cycle are interphase, nuclear division, and cytokinesis. Cell division produces two daughter cells. In cells without a nucleus (prokaryotic), the cell cycle occurs via binary fission. Interphase Gap1(G1)- Cells increase in size. The G1checkpointcontrol mechanism ensures that everything is ready for DNA synthesis. Synthesis(S)- DNA replication occurs during this phase. DNA Replication The process in which DNA makes a duplicate copy of itself. Semiconservative Replication The process in which the DNA molecule uncoils and separates into two strands. Each original strand becomes a template on which a new strand is constructed, resulting in two DNA molecules identical to the original DNA molecule. Gap 2(G2)- The cell continues to grow. The G2checkpointcontrol mechanism ensures that everything is ready to enter the M (mitosis) phase and divide. Mitotic(M) refers to the division of the nucleus. Cell growth stops at this stage and cellular energy is focused on the orderly division into daughter cells. A checkpoint in the middle of mitosis (Metaphase Checkpoint) ensures that the cell is ready to complete cell division. The final event is cytokinesis, in which the cytoplasm divides and the single parent cell splits into two daughter cells. Reproduction Cellular reproduction is a process by which cells duplicate their contents and then divide to yield multiple cells with similar, if not duplicate, contents. Mitosis Mitosis- nuclear division resulting in the production of two somatic cells having the same genetic complement (genetically identical) as the original cell.