Dynamics of DNA Replication in a Eukaryotic Cell
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Introduction of Human Telomerase Reverse Transcriptase to Normal Human Fibroblasts Enhances DNA Repair Capacity
Vol. 10, 2551–2560, April 1, 2004 Clinical Cancer Research 2551 Introduction of Human Telomerase Reverse Transcriptase to Normal Human Fibroblasts Enhances DNA Repair Capacity Ki-Hyuk Shin,1 Mo K. Kang,1 Erica Dicterow,1 INTRODUCTION Ayako Kameta,1 Marcel A. Baluda,1 and Telomerase, which consists of the catalytic protein subunit, No-Hee Park1,2 human telomerase reverse transcriptase (hTERT), the RNA component of telomerase (hTR), and several associated pro- 1School of Dentistry and 2Jonsson Comprehensive Cancer Center, University of California, Los Angeles, California teins, has been primarily associated with maintaining the integ- rity of cellular DNA telomeres in normal cells (1, 2). Telomer- ase activity is correlated with the expression of hTERT, but not ABSTRACT with that of hTR (3, 4). Purpose: From numerous reports on proteins involved The involvement of DNA repair proteins in telomere main- in DNA repair and telomere maintenance that physically tenance has been well documented (5–8). In eukaryotic cells, associate with human telomerase reverse transcriptase nonhomologous end-joining requires a DNA ligase and the (hTERT), we inferred that hTERT/telomerase might play a DNA-activated protein kinase, which is recruited to the DNA role in DNA repair. We investigated this possibility in nor- ends by the DNA-binding protein Ku. Ku binds to hTERT mal human oral fibroblasts (NHOF) with and without ec- without the need for telomeric DNA or hTR (9), binds the topic expression of hTERT/telomerase. telomere repeat-binding proteins TRF1 (10) and TRF2 (11), and Experimental Design: To study the effect of hTERT/ is thought to regulate the access of telomerase to telomere DNA telomerase on DNA repair, we examined the mutation fre- ends (12, 13). -
T-Loops and the Origin of Telomeres E
PERSPECTIVES 66. Steinman, R. M., Mellman, I. S., Muller, W. A. & Cohn, Z. A. Acknowledgments eukaryotes evolved. The presence of t-loops at Endocytosis and the recycling of plasma membrane. H.S. is supported by the Norwegian Cancer Society and the J. Cell Biol. 96, 1–27 (1983). Research Council of Norway, and J.G. by the Swiss National present-day telomeres and their association 67. Lafont, F., Lecat, S., Verkade, P. & Simons, K. Annexin Science Foundation and the Human Frontier Science Programme with proteins that have evolved from RDR XIIIb associates with lipid microdomains to function in Organization. apical delivery. J. Cell Biol. 142, 1413–1427 (1998). factors might be remnants of the original 68. Aniento, F., Gu, F., Parton, R. & Gruenberg, J. Competing interests statement telomere system. Furthermore, the relative An endosomal βcop is involved in the pH-dependent The authors declare that they have no competing financial interests. formation of transport vesicles destined for late ease with which many eukaryotes can main- endosomes. J. Cell Biol. 133, 29–41 (1996). tain telomeres without telomerase might 69. Gu, F., Aniento, F., Parton, R. & Gruenberg, J. Functional Online links dissection of COP-I subunits in the biogenesis of reflect this ancient system of chromosome-end multivesicular endosomes. J. Cell Biol. 139, 1183–1195 DATABASES replication. This proposal ends with a dis- (1997). The following terms in this article are linked online to: 70. Gu, F. & Gruenberg, J. ARF1 regulates pH-dependent Interpro: http://www.ebi.ac.uk/interpro/ cussion of the advantages of the telom- COP functions in the early endocytic pathway. -
Telomeres.Pdf
Telomeres Secondary article Elizabeth H Blackburn, University of California, San Francisco, California, USA Article Contents . Introduction Telomeres are specialized DNA–protein structures that occur at the ends of eukaryotic . The Replication Paradox chromosomes. A special ribonucleoprotein enzyme called telomerase is required for the . Structure of Telomeres synthesis and maintenance of telomeric DNA. Synthesis of Telomeric DNA by Telomerase . Functions of Telomeres Introduction . Telomere Homeostasis . Alternatives to Telomerase-generated Telomeric DNA Telomeres are the specialized chromosomal DNA–protein . Evolution of Telomeres and Telomerase structures that comprise the terminal regions of eukaryotic chromosomes. As discovered through studies of maize and somes. One critical part of this protective function is to fruitfly chromosomes in the 1930s, they are required to provide a means by which the linear chromosomal DNA protect and stabilize the genetic material carried by can be replicated completely, without the loss of terminal eukaryotic chromosomes. Telomeres are dynamic struc- DNA nucleotides from the 5’ end of each strand of this tures, with their terminal DNA being constantly built up DNA. This is necessary to prevent progressive loss of and degraded as dividing cells replicate their chromo- terminal DNA sequences in successive cycles of chromo- somes. One strand of the telomeric DNA is synthesized by somal replication. a specialized ribonucleoprotein reverse transcriptase called telomerase. Telomerase is required for both -
DNA Replication
9 DNA Replication To understand the chemistry Living cells must be able to duplicate their entire set of genetic instructions Goal of DNA synthesis and how every time they divide. Likewise, multicellular organisms must be able to DNA is replicated with high pass on complete copies of their genetic information to future generations. accuracy. This requires that the instructions are stored in a form that is capable of Objectives being duplicated. As we have seen (and will return to in Chapter 11), genetic instructions are embedded in the order of nucleobases in the DNA. As we After this chapter, you should be able to have also seen, the self-complementary nature of the double helix provides • describe the experiment that proved a simple (in principle) templating mechanism for replicating DNA into two that DNA replication is semi- identical copies. Only DNA (and in some instances RNA when, as in the conservative. case of the genomes of RNA viruses, it is used as a repository of genetic • diagram the reaction for information) are self-complementary and hence capable of being replicated. phosphodiester bond formation. The other three categories of macromolecules—carbohydrates, lipids, and • explain the energetics of DNA proteins—are not self-complementary and do not serve as templates for synthesis. their own production. Instead, the synthesis of these macromolecules is • explain why the 5’-to-3’ rule creates a ultimately directed by information stored in DNA through the action of conundrum during replication. enzymes and other proteins. Here we focus on the chemical and enzymatic • explain how DNA is replicated mechanisms by which DNA acts as a template for its own duplication and accurately. -
Getting Ready for DNA Duplication
INSIGHT INTRACELLULAR ORGANIZATION Getting ready for DNA duplication The discovery of a biomolecular condensate involved in DNA replication has wide-ranging implications. NINA Y YAO AND MICHAEL E O’DONNELL involves regions with different physical proper- Related research article Parker MW, Bell ties separating from each other). The molecules M, Mir M, Kao JA, Darzacq X, Botchan MR, required for the formation of condensates are Berger JM. 2019. A new class of disordered called scaffolding factors, while the molecules elements controls DNA replication through encapsulated inside are known as clients. A initiator self-assembly. eLife 8:e48562. DOI: given condensate typically contains only those 10.7554/eLife.48562 clients involved in the relevant reaction. Now, in eLife, Michael Botchan (UC Berkeley), James Berger (Johns Hopkins) and colleagues – including Matthew Parker as first author – report on the discovery of a biomolecular condensate esearch into biomolecular condensates – required for the initiation of DNA replication in self-contained regions within cells where the fruit fly Drosophila melanogaster R specific reactions take place – is taking (Parker et al., 2019). Three proteins – ORC, cell biology by storm. Biomolecular condensates Cdc6 and Cdt1 – form the scaffold along with do not have membranes, but they are able to DNA, while a hexamer ring protein called keep the proteins and/or nucleic acids involved Mcm2-7 is the client. During the G1 phase of the in a particular reaction separate from the rest of cell cycle, the scaffold proteins load two Mcm2- the cell. Biomolecular condensates do not have 7 hexamers onto the DNA to form the pre-repli- membranes, but they are able to keep the mole- cative complex, which marks the spot where cules involved in a particular reaction (usually DNA replication will begin (Figure 1A–C; proteins, but sometimes also nucleic acids) sepa- Bell and Labib, 2016; Bleichert et al., 2017). -
Telomere and Telomerase in Oncology
Cell Research (2002); 12(1):1-7 http://www.cell-research.com REVIEW Telomere and telomerase in oncology JIAO MU*, LI XIN WEI International Joint Cancer Institute, Second Military Medical University, Shanghai 200433, China ABSTRACT Shortening of the telomeric DNA at the chromosome ends is presumed to limit the lifespan of human cells and elicit a signal for the onset of cellular senescence. To continually proliferate across the senescent checkpoint, cells must restore and preserve telomere length. This can be achieved by telomerase, which has the reverse transcriptase activity. Telomerase activity is negative in human normal somatic cells but can be detected in most tumor cells. The enzyme is proposed to be an essential factor in cell immortalization and cancer progression. In this review we discuss the structure and function of telomere and telomerase and their roles in cell immortalization and oncogenesis. Simultaneously the experimental studies of telomerase assays for cancer detection and diagnosis are reviewed. Finally, we discuss the potential use of inhibitors of telomerase in anti-cancer therapy. Key words: Telomere, telomerase, cancer, telomerase assay, inhibitor. Telomere and cell replicative senescence base pairs of the end of telomeric DNA with each Telomeres, which are located at the end of round of DNA replication. Hence, the continual chromosome, are crucial to protect chromosome cycles of cell growth and division bring on progress- against degeneration, rearrangment and end to end ing telomere shortening[4]. Now it is clear that te- fusion[1]. Human telomeres are tandemly repeated lomere shortening is responsible for inducing the units of the hexanucleotide TTAGGG. The estimated senescent phenotype that results from repeated cell length of telomeric DNA varies from 2 to 20 kilo division, but the mechanism how a short telomere base pairs, depending on factors such as tissue type induces the senescence is still unknown. -
Ch 7 -Brock Information Flow in Biological Systems
Systems Microbiology Monday Oct 2 - Ch 7 -Brock Information flow in biological systems •• DNADNA replicationreplication •• TranscriptionTranscription •• TranslationTranslation Central Dogma DNA Replication Transcription Images removed due to copyright restrictions. RNA Reverse Transcription Translation Protein Flow of information replication DNA → DNA transcription ↓ RNA translation ↓ protein 5' end ring numbering system for -P-O-C deoxyribose 5’ -C O O 4’ 1’ P O- O 3’ 2’ C ssDNA 3’ end HO In a nucleotide, e.g., adenosine monophosphate (AMP), the base is bonded to a ribose sugar, which has a phosphate in ester linkage to the 5' hydroxyl. NH NH NH2 2 2 adenine N N N N N N N N N N N N H −2 HO O3P O CH CH 5' 2 O 2 O 4' H H 1' H H ribose H 3' 2' H H H OH OH OH OH adenine adenosine adenosine monophosphate (AMP) Nucleic acids have a NH2 backbone of adenine N N alternating Pi & ribose moieties. N NH − N 2 Phosphodiester 5' end O cytosine − 5' O P O CH N linkages form as the 2 O 4' 1' O H H ribose 5' phosphate of one N O H 3' 2' H nucleotide forms an O OH − 5' ester link with the 3' O P O CH 2 O OH of the adjacent O H H ribose nucleotide. H 3' H O OH − O P O (etc) nucleic acid 3' end O H N H O N Guanine Cytosine N H N N N N O H N Backbone Backbone Hydrogen H bond H O H N CH3 N Thymine N H N N Adenine N N Hydrogen O bond Backbone Backbone Figure by MIT OCW. -
How to Rule the Nucleus: Divide Et Impera
Available online at www.sciencedirect.com ScienceDirect How to rule the nucleus: divide et impera 1 1 1,2 Irina Solovei , Katharina Thanisch and Yana Feodorova Genome-wide molecular studies have provided new insights conserved and serve as functional platforms for into the organization of nuclear chromatin by revealing the physical interactions between regulatory elements [6– presence of chromatin domains of differing transcriptional 8]. Various other domains, such as lamina-associated activity, frequency of cis-interactions, proximity to scaffolding domains (LADs) [9,10 ,11], nucleolus-associated structures and replication timing. These studies have not only domains (NADs) [12] or pericentromere-associated brought our understanding of genome function to a new level, domains (PADs) [13 ], have been implicated in organiz- but also offered functional insight for many phenomena ing and anchoring the genome within the nucleus. In observed in microscopic studies. In this review, we discuss the cycling cells, genomic regions with time-coordinated major principles of nuclear organization based on the spatial replication form replication domains [14–17]. segregation of euchromatin and heterochromatin, as well as the dynamic genome rearrangements occurring during cell Although the fine details of genome organization and its differentiation and development. We hope to unite the existing functional connections to transcription regulation have molecular and microscopic data on genome organization to get been thoroughly discussed in a plethora of recent reviews a holistic view of the nucleus, and propose a model, in which (e.g., this COCB issue, see also [17–24], it remains a repeat repertoire together with scaffolding structures blueprint challenge to integrate the genomics-based and microsco- the functional nuclear architecture. -
DNA REPLICATION, REPAIR, and RECOMBINATION Figure 5–1 Different Proteins Evolve at Very Different Rates
5 THE MAINTENANCE OF DNA DNA REPLICATION, SEQUENCES DNA REPLICATION MECHANISMS REPAIR, AND THE INITIATION AND COMPLETION OF DNA REPLICATION IN RECOMBINATION CHROMOSOMES DNA REPAIR GENERAL RECOMBINATION SITE-SPECIFIC RECOMBINATION The ability of cells to maintain a high degree of order in a chaotic universe depends upon the accurate duplication of vast quantities of genetic information carried in chemical form as DNA. This process, called DNA replication, must occur before a cell can produce two genetically identical daughter cells. Main- taining order also requires the continued surveillance and repair of this genetic information because DNA inside cells is repeatedly damaged by chemicals and radiation from the environment, as well as by thermal accidents and reactive molecules. In this chapter we describe the protein machines that replicate and repair the cell’s DNA. These machines catalyze some of the most rapid and accu- rate processes that take place within cells, and their mechanisms clearly demon- strate the elegance and efficiency of cellular chemistry. While the short-term survival of a cell can depend on preventing changes in its DNA, the long-term survival of a species requires that DNA sequences be changeable over many generations. Despite the great efforts that cells make to protect their DNA, occasional changes in DNA sequences do occur. Over time, these changes provide the genetic variation upon which selection pressures act during the evolution of organisms. We begin this chapter with a brief discussion of the changes that occur in DNA as it is passed down from generation to generation. Next, we discuss the cellular mechanisms—DNA replication and DNA repair—that are responsible for keeping these changes to a minimum. -
Genome-Wide Dynamics of Replication Timing Revealed by in Vitro Models of Mouse Embryogenesis
Downloaded from genome.cshlp.org on September 26, 2021 - Published by Cold Spring Harbor Laboratory Press Article Genome-wide dynamics of replication timing revealed by in vitro models of mouse embryogenesis Ichiro Hiratani,1 Tyrone Ryba,1 Mari Itoh,1 Joy Rathjen,2 Michael Kulik,3 Bernadett Papp,4 Eden Fussner,5 David P. Bazett-Jones,5 Kathrin Plath,4 Stephen Dalton,3 Peter D. Rathjen,2 and David M. Gilbert1,6 1Department of Biological Science, Florida State University, Tallahassee, Florida 32306, USA; 2Department of Zoology, University of Melbourne, Parkville, Victoria 3010, Australia; 3Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA; 4University of California Los Angeles, David Geffen School of Medicine, Department of Biological Chemistry, Jonsson Comprehensive Cancer Center, Molecular Biology Institute, Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, Los Angeles, California 90024, USA; 5Program in Genetics and Genome Biology, The Hospital for Sick Children, Research Institute, Toronto, Ontario M5G 1L7, Canada Differentiation of mouse embryonic stem cells (mESCs) is accompanied by changes in replication timing. To explore the relationship between replication timing and cell fate transitions, we constructed genome-wide replication-timing profiles of 22 independent mouse cell lines representing 10 stages of early mouse development, and transcription profiles for seven of these stages. Replication profiles were cell-type specific, with 45% of the genome exhibiting significant changes at some point during development that were generally coordinated with changes in transcription. Comparison of early and late epiblast cell culture models revealed a set of early-to-late replication switches completed at a stage equivalent to the post- implantation epiblast, prior to germ layer specification and down-regulation of key pluripotency transcription factors [POU5F1 (also known as OCT4)/NANOG/SOX2] and coinciding with the emergence of compact chromatin near the nuclear periphery. -
Working on Genomic Stability: from the S-Phase to Mitosis
G C A T T A C G G C A T genes Review Working on Genomic Stability: From the S-Phase to Mitosis Sara Ovejero 1,2,3,* , Avelino Bueno 1,4 and María P. Sacristán 1,4,* 1 Instituto de Biología Molecular y Celular del Cáncer (IBMCC), Universidad de Salamanca-CSIC, Campus Miguel de Unamuno, 37007 Salamanca, Spain; [email protected] 2 Institute of Human Genetics, CNRS, University of Montpellier, 34000 Montpellier, France 3 Department of Biological Hematology, CHU Montpellier, 34295 Montpellier, France 4 Departamento de Microbiología y Genética, Universidad de Salamanca, Campus Miguel de Unamuno, 37007 Salamanca, Spain * Correspondence: [email protected] (S.O.); [email protected] (M.P.S.); Tel.: +34-923-294808 (M.P.S.) Received: 31 January 2020; Accepted: 18 February 2020; Published: 20 February 2020 Abstract: Fidelity in chromosome duplication and segregation is indispensable for maintaining genomic stability and the perpetuation of life. Challenges to genome integrity jeopardize cell survival and are at the root of different types of pathologies, such as cancer. The following three main sources of genomic instability exist: DNA damage, replicative stress, and chromosome segregation defects. In response to these challenges, eukaryotic cells have evolved control mechanisms, also known as checkpoint systems, which sense under-replicated or damaged DNA and activate specialized DNA repair machineries. Cells make use of these checkpoints throughout interphase to shield genome integrity before mitosis. Later on, when the cells enter into mitosis, the spindle assembly checkpoint (SAC) is activated and remains active until the chromosomes are properly attached to the spindle apparatus to ensure an equal segregation among daughter cells. -
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.