A number of proteins have been isolated from human cells on the basis of their ability to support DNA replication in vitro of the simian virus 40 (SV40) origin of DNA replication. One such protein, replication factor C (RFC), functions with the proliferating cell nuclear antigen (PCNA), replication protein A (RPA), and DNA polymerase delta to synthesize the leading strand at a replication fork. To determine whether these proteins perform similar roles during replication of DNA from origins in cellular chromosomes, we have begun to characterize functionally homologous proteins from the yeast Saccharomyces cerevisiae. RFC from S. cerevisiae was purified by its ability to stimulate yeast DNA polymerase delta on a primed single-stranded DNA template in the presence of yeast PCNA and RPA. Like its human-cell counterpart, RFC from S. cerevisiae (scRFC) has an associated DNA-activated ATPase activity as well as a primer-template, structure-specific DNA binding activity. By analogy with the phage T4 and ...
TY - JOUR. T1 - The DNA Replication Program Is Altered at the FMR1 Locus in Fragile X Embryonic Stem Cells. AU - Gerhardt, Jeannine. AU - Tomishima, Mark J.. AU - Zaninovic, Nikica. AU - Colak, Dilek. AU - Yan, Zi. AU - Zhan, Qiansheng. AU - Rosenwaks, Zev. AU - Jaffrey, Samie R.. AU - Schildkraut, Carl L.. PY - 2014/1/9. Y1 - 2014/1/9. N2 - Fragile X syndrome (FXS) is caused by a CGG repeat expansion in the FMR1 gene that appears to occur during oogenesis and during early embryogenesis. One model proposes that repeat instability depends on the replication fork direction through the repeats such that (CNG)n hairpin-like structures form, causing DNA polymerase to stall and slip. Examining DNA replication fork progression on single DNA molecules at the endogenous FMR1 locus revealed that replication forks stall at CGG repeats in human cells. Furthermore, replication profiles of FXS human embryonic stem cells (hESCs) compared to nonaffected hESCs showed that fork direction through the repeats is ...
Replication of the two template strands at eukaryotic cell DNA replication forks is a highly coordinated process that ensures accurate and efficient genome duplication. Biochemical studies, principally of plasmid DNAs containing the Simian Virus 40 origin of DNA replication, and yeast genetic studies have uncovered the fundamental mechanisms of replication fork progression. At least two different DNA polymerases, a single-stranded DNA-binding protein, a clamp-loading complex, and a polymerase clamp combine to replicate DNA. Okazaki fragment synthesis involves a DNA polymerase-switching mechanism, and maturation occurs by the recruitment of specific nucleases, a helicase, and a ligase. The process of DNA replication is also coupled to cell-cycle progression and to DNA repair to maintain genome integrity.. ...
Previous genetic studies in yeast suggested that Pol ε plays an important role during chromosomal DNA replication [1, 7-9]. However, because the amino-terminal portion of Pol ε, that is required for its DNA polymerase- and exonuclease activities, is dispensable for yeast DNA replication, repair, and viability [15, 16, 27], the role of Pol ε during DNA replication has remained obscure. This study explores this role using an in vitro Xenopus DNA replication system and wild type and mutant forms of r-xPol ε holoenzyme. Here we show that the DNA replication defect in xPol ε-depleted Xenopus egg extracts is readily corrected by native (n-xPol ε) (data not shown and [22]) or recombinant xPol ε (r-xPol ε) holoenzyme or the p260-p60 Pol ε sub-complex, but not by p260ΔCat holoenzyme, p260 DN, p260 or p260-p12-p17 (Fig. 4). Because the former enzymes are polymerase proficient, while p260ΔCat holoenzyme and p260 DN are polymerase-deficient, although these preparations contained a small amount of ...
A complex network of interacting proteins and enzymes is required for DNA replication. Generally, DNA replication follows a multistep enzymatic pathway. At the DNA replication fork, a DNA helicase (DnaB or MCM complex) precedes the DNA synthetic machinery and unwinds the duplex parental DNA in cooperation with the SSB or RPA. On the leading strand, replication occurs continuously in a 5 to 3 direction, whereas on the lagging strand, DNA replication occurs discontinuously by synthesis and joining of short Okazaki fragments. In prokaryotes, the leading strand replication apparatus consists of a DNA polymerase (pol III core), a sliding clamp (beta), and a clamp loader (gamma delta complex). The DNA primase (DnaG) is needed to form RNA primers. Normally, during replication of the lagging-strand DNA template, an RNA primer is removed either by an RNase H or by the 5 to 3 exonuclease activity of DNA pol I, and the DNA ligase joins the Okazaki fragments. In eukaryotes, three DNA polymerases (alpha, ...
A complex network of interacting proteins and enzymes is required for DNA replication. Generally, DNA replication follows a multistep enzymatic pathway. At the DNA replication fork, a DNA helicase (DnaB or MCM complex) precedes the DNA synthetic machinery and unwinds the duplex parental DNA in cooperation with the SSB or RPA. On the leading strand, replication occurs continuously in a 5 to 3 direction, whereas on the lagging strand, DNA replication occurs discontinuously by synthesis and joining of short Okazaki fragments. In prokaryotes, the leading strand replication apparatus consists of a DNA polymerase (pol III core), a sliding clamp (beta), and a clamp loader (gamma delta complex). The DNA primase (DnaG) is needed to form RNA primers. Normally, during replication of the lagging-strand DNA template, an RNA primer is removed either by an RNase H or by the 5 to 3 exonuclease activity of DNA pol I, and the DNA ligase joins the Okazaki fragments. In eukaryotes, three DNA polymerases (alpha, ...
DNA replication is a tightly regulated multistep process that requires the sequential action of several protein complexes that select DNA replication origins, recruit on these origins the DNA replication fork helicase that once activated, unwinds and duplicates the DNA. These events must be tightly coupled to cell cycle progression to ensure that DNA replication occurs once and only once per cell cycle.. DNA replication is thus temporally separated into two steps that are controlled by Cyclin-Dependent Kinase (CDK) activity. The first step, which occurs in mitosis and during the G1 phase of the cell cycle, when Cdk activity is low, involves the loading of a double hexameric Mcm2-7 (minichromosome maintenance 2-7) complex on the chromatin as part of the prereplicative complex (pre-RC) (Evrin et al. 2009; Remus et al. 2009; Gambus et al. 2011; Deegan and Diffley 2016). Pre-RC formation requires several loading factors including the hexameric Origin Recognition Complex (ORC-1-6), and Cdc6 and Cdt1 ...
please provide good explanation1- compare the dna replication process in cells with the process occurring in the pcr, Hire Biology Expert, Ask Academics Expert, Assignment Help, Homework Help, Textbooks Solutions
Chapter 3: DNA Replication Models of DNA replication: Meselson-Stahl Experiment DNA synthesis and elongation DNA polymerases Origin and initiation of DNA replication Prokaryote/eukaryote models (circular/linear chromosomes) Telomere replication Slideshow 29909 by JasminFlorian
TY - JOUR. T1 - Genetic control of the cell division cycle in yeast. II. Genes controlling DNA replication and its initiation. AU - Hartwell, Leland H.. PY - 1971/7/14. Y1 - 1971/7/14. N2 - Temperature-sensitive mutations occurring in two unlinked complementation groups, cdc4 and cdc8, are recessive and result in a defect in DNA replication at the restrictive temperature. Results obtained with synchronous cultures suggest that cdc4 functions in the initiation of DNA replication and cdc8 functions in the propagation of DNA replication. From the behavior of mutant strains carrying lesions in cdc4, or in cdc8, or in both genes it is concluded that: (1) nuclear division and cell separation in yeast are dependent upon prior DNA replication; (2) a cellular clock controls bud initiation and the running of this clock is independent of the other events in the cycle, DNA replication, nuclear division and cell separation; (3) premature bud initiation is normally prevented as a consequence of the successful ...
Flow cytometry, a method for measuring DNA content, also gives information about the cell cycle. Non-cycling cells are said to be in the G0 stage. For cycling cells, it is usual to define four distinct phases of the cell cycle. Mitosis (M phase) is followed by the G1 phase (gap 1). During this phase the cell continuously grows but does not replicate its DNA. When the cell starts to make new DNA it has entered the S (DNA synthesis) phase. The completion of DNA synthesis is followed by the G2 phase (gap 2), during which cell growth continues and proteins are synthesised in preparation for mitosis [1]. Flow cytometry has been shown to be very suitable for determining the DNA replication stages in seeds [2,3,10,11,16,17,18]. In commercial practice, sugar beet seeds are often washed/soaked and treated with fungicides before sowing. These treatments are intended to leach out the soluble inhibitors from the pericarp and to control damping off, which, in turn, improve seed performance in the field ...
AMONG the genetic and epigenetic changes to genomes, changes in ploidy are the most drastic, and as such, polyploidy is not tolerated by most animal species (Li et al. 2009a). A recent study of tetraploid yeast suggests that the deleterious effects of ploidy change are due to the uncoordinated scaling of the spindle pole body, spindle, and kinetochore, thus resulting in genetic instability (GIN) (Storchova et al. 2006). However, ploidy changes occur in every sexual cycle of all eukaryotes and are associated with the inclusion or exclusion of an entire set of chromosome homologs that significantly alters the DNA repair capacity. Little is known about whether DNA damage response is regulated differently in haplophase and diplophase during sexual cycles.. DNA replication stress, induced by oncogene activation, genotoxic stress, or defects in the DNA replication machinery, is believed to cause GIN that accelerates tumorigenesis (Halazonetis et al. 2008). However, DNA replication stress does not ...
Dates: 7 - 10 May 2018 Registration: 26 Mar 18 Abstract: 12 Feb 18 Event webpage: www.embo-embl-symposia.org/symposia/2018/EES18-02/index.html Aim:There has been tremendous progress in the past few years regarding our understanding of DNA replication in eukaryotes, both yeast and mammals. Many important questions in the field are poised to be answered within the next decade. These include understanding DNA replication at the biochemical and three-dimensional protein structure levels. In addition, studies using high throughput technologies at the cellular and organismal levels are poised to answer how accurate replication of the genome is ensured by controlling origin firing in space and time.Several human diseases, including cancer, have already been linked to DNA replication stress, a term that refers to perturbations in DNA replication. Thus, a better understanding of how cells respond to DNA replication stress will help us understand disease development and responses to therapy. By bringing ...
Mammalian mitochondria operate multiple mechanisms of DNA replication. In many cells and tissues a strand-asynchronous mechanism predominates over coupled leading and lagging-strand DNA synthesis. However, little is known of the factors that control or influence the different mechanisms of replication, and the idea that strand-asynchronous replication entails transient incorporation of transcripts (aka bootlaces) is controversial. A firm prediction of the bootlace model is that it depends on mitochondrial transcripts. Here, we show that elevated expression of Twinkle DNA helicase in human mitochondria induces bidirectional, coupled leading and lagging-strand DNA synthesis, at the expense of strand-asynchronous replication; and this switch is accompanied by decreases in the steady-state level of some mitochondrial transcripts. However, in the so-called minor arc of mitochondrial DNA where transcript levels remain high, the strand-asynchronous replication mechanism is instated. Hence, replication ...
Chromosome replication in eukaryotic cells is regulated in a highly complex fashion in order to maintain the integrity of the genome from one generation to the next. DNA replication forks are established at different moments in time during S‐phase from multiple origins on each chromosome, yet initiation at each origin can occur just once, so that a single copy of the genome is generated in each round of a typical cell cycle (Blow and Dutta, 2005). This is achieved by dividing the cell cycle into a period when prereplication complexes (pre‐RCs) of proteins essential for initiation are assembled at origins but cannot be activated, and a subsequent and mutually exclusive period when pre‐RCs can be activated but can no longer form (Diffley et al, 1994). At each origin, the pre‐RC is lost during initiation, so that each region of the chromosome is replicated precisely once during each cell cycle.. The key event in the formation of pre‐RCs-also known as the licensing of origins-is the ...
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for natural inheritance. The process starts when one double-stranded DNA molecule produces two identical copies of the molecule. The cell cycle (mitosis) also pertains to the DNA replication/reproduction process. DNA replication, in eukaryotes, is controlled within the context of the cell cycle. As the cell grows and divides, it goes through stages in the cell cycle; DNA replication occurs during the S phase (synthesis phase). Whereas bacteria do not go through an exact cell cycle but instead, they continuously copy their DNA. The research conducted in this study was to see if, in fact, that cell size had anything to do with the initiation of DNA replication in bacteria. The objectives and hypothesis was clearly stated in the paper. In order to find the answer to their question, the researchers used Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) in their experiment. ...
Cyclin-dependent kinases (CDKs) regulate the progression of the cell cycle in eukaryotes. One of the major roles of CDK is to promote chromosomal DNA replication. However, how CDKs promote DNA replication has been a long-standing question, because all the essential CDK substrates in DNA replication have not been identified yet. Recently Sld2 and Sld3 were identified as essential substrates of CDKs in the initiation step of DNA replication in budding yeast. Moreover, bypass of their phosphorylations is sufficient to promote DNA replication. Phosphorylation of Sld2 and Sld3 by CDKs enhances the formation of complex(es) with a BRCT (BRCA1 C-Terminal)-containing replication protein, Dpb11. We further propose that multiple phosphorylation by CDKs controls this process in budding yeast. Even though Sld3 orthologues in multicellular eukaryotes have not been identified, similar complex formation and, therefore, a similar mechanism of initiation control might be employed in eukaryotes.
Maintaining replication fork integrity is vital to preserve genomic stability and avoid cancer. Physical DNA damage and altered nucleotide or protein pools represent replication obstacles, generating replicative stress. Numerous cellular responses have evolved to ensure faithful DNA replication despite such challenges. Understanding those responses is essential to understand and prevent or treat replication-associated diseases, such as cancer.. Re-priming is a mechanism to allow resumption of DNA synthesis past a fork-stalling lesion. This was recently suggested in yeast and explains the formation of gaps during DNA replication on damaged DNA. Using a combination of assays, we indicate the existence of re-priming also in human cells following UV irradiation.. The gap left behind a re-primed fork must be stabilised to avoid replication-associated collapse. Our results show that the checkpoint signalling protein CHK1 is dispensable for stabilisation of replication forks after UV irradiation, ...
The DNA replication checkpoint is a complex signal transduction pathway, present in all eukaryotic cells, that functions to maintain genomic integrity and cell viability when DNA replication is perturbed. In Schizosaccharomyces pombe the major effector of the replication checkpoint is the protein kinase Cds1. Activation of Cds1 is known to require the upstream kinase Rad3 and the mediator Mrc1, but the biochemical mechanism of activation is not well understood. We report that the replication checkpoint is activated in two stages. In the first stage, Mrc1 recruits Cds1 to stalled replication forks by interactions between the FHA domain of Cds1 and specific phosphorylated Rad3 consensus sites in Mrc1. Cds1 is then primed for activation by Rad3-dependent phosphorylation. In the second stage, primed Cds1 molecules dimerize via phospho-specific interactions mediated by the FHA domains and are activated by autophosphorylation. This two-stage activation mechanism for the replication checkpoint allows for rapid
The cohesin complex holds together newly-replicated chromatids and is involved in diverse pathways that preserve genome integrity. We show that in budding yeast, cohesin is transiently recruited to active replication origins and it spreads along DNA as forks progress. When DNA synthesis is impeded, cohesin accumulates at replication sites and is critical for the recovery of stalled forks. Cohesin enrichment at replication forks does not depend on H2A(X) formation, which differs from its loading requirements at DNA double-strand breaks (DSBs). However, cohesin localization is largely reduced in rad50delta mutants and cells lacking both Mec1 and Tel1 checkpoint kinases. Interestingly, cohesin loading at replication sites depends on the structural features of Rad50 that are important for bridging sister chromatids, including the CXXC hook domain and the length of the coiled-coil extensions. Together, these data reveal a novel function for cohesin in the maintenance of genome integrity during S phase. Scc1
DNA-skadande ämnen är vanligt i cancerbehandling, då snabbt växande celler, såsom cancerceller är betydligt känsligare än normala celler för DNA skador. En grupp av ämnen som vanligen används i cancerbehandling är korsbindare av DNA. Dessa ämnen kommer reagera två gånger med DNA och skapa två bindningar mitt emot varandra. DNA strängen, som består av två delar, måste kunna separeras och kopieras (replikation) på ett tillförlitligt sätt för att cellerna ska kunna dela sig och bli flera. DNA strängen måste också kunna dela sig och bli avläst rätt för att nya proteiner ska kunna bildas (transkription). När korsbindarna har bundit till DNA strängarna, hindrar detta deras separation och därigenom förhindras även avläsningen och kopieringen. För att göra undersökningarna av DNA korsbindande ämnen ännu lite svårare, så ger korsbindare flera olika typer av skador. Dels kan det bli flera olika typer av korsbindningar, både mellan två DNA-strängar (ICL) vilket ...
Professor Emeritus Department of Biochemistry Rosalind and Morris Goodman Cancer Centre [email protected] 1979 - PhD, McGill University Research Interests Isolation and characterization of mammalian origins of DNA replication Our primary research interest is in the molecular basis of the mechanisms regulating mammalian DNA replication. Eukaryotic chromosomes are organized into multiple replication units that initiate replication only one per cell cycle. The mechanism that prevents the reinitiation of replication of DNA that has been previously replicated is unknown. Among the major questions about mammalian DNA replication are: 1) whether initiation occurs at specific DNA sequences (replication origins), and 2) what are the molecular features of these sequences. Using the instability of replication loops as a method for the isolation of active replication origins, we have purified and cloned DNA sequences that contain origins of replication. In this manner we have generated libraries of monkey and
PUFs are RNA binding proteins that promote mRNA deadenylation and decay and inhibit translation. Yeast Puf5 is the prototype for studying PUF-dependent gene repression. Puf5 binds to the Pop2 subunit of the Ccr4-Pop2-NOT mRNA deadenylase, recruiting the deadenylase and associated translational repressors to mRNAs. Here we used yeast genetics to show that Puf5 has additional roles in vivo that do not require Pop2. Deletion of PUF5 caused increased sensitivity to DNA replication stress in cells lacking Pop2, as well as in cells mutated for two activities recruited to mRNAs by the Puf5-Pop2 interaction, the deadenylase Ccr4 and the translational repressor Dhh1. A functional Puf5 RNA binding domain was required, and Puf5 cytoplasmic localisation was sufficient for resistance to replication stress, indicating posttranscriptional gene expression control is involved. In contrast to DNA replication stress, in response to the cell wall integrity pathway activator caffeine, PUF5 and POP2 acted in the same genetic
DNA replication is typically highly processive. Replication fork stalling or arrest can result when replication forks encounter damage in the DNA, and at naturally occurring sequences such as replication fork barriers and replication slow zones (Rothstein et al., 2000; Cha and Kleckner, 2002). Several mechanisms by which replication forks can be restarted following arrest have been described in bacteria (reviewed in Michel, 2000; Michel et al., 2001). Stalled forks are susceptible to breakage and to replication fork reversal, both of which generate a double‐stranded DNA end. A replication fork can then be re‐established by homologous recombination followed by Holliday junction resolution or by branch migration. By analogy, some of these same processes are believed to occur in eukaryotes. In addition to these pathways, which are principally involved in restarting what are presumably collapsed replication forks, recent work has demonstrated that the S phase checkpoint pathway is responsible ...
The herpes simplex virus (HSV) genome contains both cis- and trans-acting elements which are important in viral DNA replication. The cis-acting elements consist of three origins of replication: two copies of oriS and one copy of oriL. It has previously been shown that five cloned restriction fragments of HSV-1 DNA together can supply all of the trans-acting functions required for the replication of plasmids containing oriS or oriL when cotransfected into Vero cells (M. D. Challberg, Proc. Natl. Acad. Sci. USA, 83:9094-9098, 1986). These observations provide the basis for a complementation assay with which to locate all of the HSV sequences which encode trans-acting functions necessary for origin-dependent DNA replication. Using this assay in combination with the data from large-scale sequence analysis of the HSV-1 genome, we have now identified seven HSV genes which are necessary for transient replication of plasmids containing either oriS or oriL. As shown previously, two of these genes encode ...
The membrane affinity of the SeqA protein tends to make it insoluble in whole-cell extracts unless the salt concentration is elevated. If SeqA protein binding forms a coherent filament of protein on the DNA with the sequences intervening between the GATC sites looped out, the newly replicated DNA would be organized and compacted as it emerges from the replication fork. The E. coli chromosome replication forks are not thought to move about the nucleoid as they progress around the chromosome. Chromosome segregation is a direct consequence of replication and occurs concomitantly with it. The DNA replication process itself drives DNA segregation, pushing the newly replicated DNA outward from the anchored replication forks toward opposite cell poles. The properties of the SeqA protein and its selective binding to the newly replicated DNA at the replication forks suggest that it might be directly involved in some or all of these processes. If the single-strand contact persisted through replication, newly
Genomic DNA replication is essential for the transmission of genetic information; during this process, minichromosome maintenance (MCM) complex, the cellular replicative helicase, unwinds duplex DNA to enable DNA synthesis by polymerases. Eukaryotic DNA replication is a tightly regulated process and the recruitment of MCM to the replication origin and its activation require the participations of the GINS complex and more than ten additional DNA replication factors. My thesis project focuses on the structural studies of the GINS complex, as well as a MCM functional homolog, Simian virus 40 (SV40) large T antigen (LTag) helicase.; The crystal structure of the full-length human GINS hetero-tetramer was determined in order to further understand the functional role of GINS. The four subunits each has a major domain composed of an α-helical bundle-like structure. With the exception of Psf1, other subunits each has a small domain containing a three-stranded β-sheet core. Each full-length protein in ...
The T4 bacteriophage encodes eight proteins, which are sufficient to carry out coordinated leading and lagging strand DNA synthesis. These purified proteins have been used to reconstitute DNA synthesis in vitro and are a well-characterized model system. Recent work on the T4 replisome has yielded more detailed insight into the dynamics and coordination of proteins at the replication fork. Since the leading and lagging strands are synthesized in opposite directions, coordination of DNA synthesis as well as priming and unwinding is accomplished by several protein complexes. These protein complexes serve to link catalytic activities and physically tether proteins to the replication fork. Essential to both leading and lagging strand synthesis is the formation of a holoenzyme complex composed of the polymerase and a processivity clamp. The two holoenzymes form a dimer allowing the lagging strand polymerase to be retained within the replisome after completion of each Okazaki fragment. The helicase and primase
A cells ability to control replication of its DNA is fundamental to its normal development or transformation into a cancerous state. DNA replication is also a crucial step in the cell cycle, and recent improvements in our understanding of cell cycle control have promoted a fresh surge of interest in the subject. In this volume, the complexities of eukaryotic DNA replication are reviewed by leaders in this rapidly advancing field.
Li J.J., Kelly T.J.. We recently described a soluble cell-free system derived from monkey cells that is capable of replicating exogenous plasmid DNA molecules containing the simian virus 40 (SV40) origin of replication (J.J. Li, and T.J. Kelly, Proc. Natl. Acad. Sci. U.S.A. 81:6973-6977, 1984). Replication in the system is completely dependent upon the addition of the SV40 large T antigen. In this report we describe additional properties of the in vitro replication reaction. Extracts prepared from cells of several nonsimian species were tested for the ability to support origin-dependent replication in the presence of T antigen. The activities of extracts derived from human cell lines HeLa and 293 were approximately the same as those of monkey cell extracts. Chinese hamster ovary cell extracts also supported SV40 DNA replication in vitro, but the extent of replication was approximately 1% of that observed with human or monkey cell extracts. No replication activity was detectable in extracts ...
Successful DNA replication and packaging of newly synthesized DNA into chromatin are essential to maintain genome integrity. Defects in the DNA template challenge genetic and epigenetic inheritance. Unfortunately, tracking DNA damage responses (DDRs), histone deposition, and chromatin maturation at replication forks is difficult in mammalian cells. Here we describe a technology called iPOND (isolation of proteins on nascent DNA) to analyze proteins at active and damaged replication forks at high resolution. Using this methodology, we define the timing of histone deposition and chromatin maturation. Class 1 histone deacetylases are enriched at replisomes and remove predeposition marks on histone H4. Chromatin maturation continues even when decoupled from replisome movement. Furthermore, fork stalling causes changes in the recruitment and phosphorylation of proteins at the damaged fork. Checkpoint kinases catalyze H2AX phosphorylation, which spreads from the stalled fork to include a large ...
To delineate the function of adenovirus early region 4 (E4) gene products, we constructed a set of mutant viruses which carry defined lesions within this coding region. Deletion and insertion mutations within six of seven known E4 coding regions had no measurable effect on virus growth in cultured cells. A variant carrying a deletion within the last coding region (encoding a 34,000-molecular-weight polypeptide) was modestly defective, and a mutant lacking the majority of the E4 region was severely defective for growth. The phenotypes of the two defective mutants are similar and complex. Both display perturbations in DNA replication, translation of the E2A mRNA, accumulation of late viral mRNAs, and host cell shutoff. ...
The GINS complex plays an essential role in the initiation of DNA replication, and progression of DNA replication forks. GINS4 is important for GINS complex assembly. GINS complex seems to bind preferentially to single-stranded DNA.
DNA replication, the basis for biological inheritance, is a fundamental process occurring in all living organisms to copy their DNA. This process is "semiconservative" in that each strand of the original double-stranded DNA molecule serves as template for the reproduction of the complementary strand. Hence, following DNA replication, two identical DNA molecules have been produced from a single double-stranded DNA molecule. Cellular proofreading and error-checking mechanisms ensure near perfect fidelity for DNA replication ...
DNA replication is the process of copying a DNA molecule to produce two identical copies. This is the main method of transmitting parental characteristics to progeny. DNA replication is semi conservative, as proposed by Watson and Crick in 1953. This means that the parental DNA unwinds to give two strands, each of which is then used as a template to synthesis a new complementary strand. Thus in each new DNA molecule, one strand is the conserved parental strand and the other is the new complement. The replication process is a complex enzyme catalysed mechanism with the involvement of associated proteins and RNA. It varies in prokaryotes and eukaryotes but the main mechanisms remain similar. Replication initiation begins at specific sites within the DNA called origin of replication. Circular prokaryotic DNA have one origin of replication while linear eukaryotic DNA have multiple origins. The origin of replication has protein binding sites to which an initiator protein can bind. This protein ...
DNA replication. Computer illustration showing a DNA (deoxyribonucleic acid) molecule being unwound to create two new identical daughter molecules (upper left and right). The DNA double helix separates into its two strands. Each strand then acts as a template for the formation of a new DNA molecule. This is known as semiconservative replication. DNA contains sections called genes, which encode the bodys genetic information. - Stock Image C026/7667
Eukaryotic cells have evolved tightly controlled processes that make sure the entire genome gets replicated accurately, once per cell cycle. This tight control is fulfilled by degrading replication proteins after their function is carried out, changing their cellular location or by post-translational modification of replication factors to regulate their function. Phosphorylation events carried out by CDKs (cyclin dependent kinases) and DDKs (Dbf4 dependent kinases) play crucial roles in this regulation. The DNA unwinding element binding protein (DUE-B) is an essential replication protein that binds to the human c-myc DNA replication origin. In this study, I find that DUE-B is also actively regulated by kinases and phosphatases. DUE-B binds to chromatin after pre-replication complex formation but before Cdc45 chromatin loading. DUE-B chromatin binding requires CDK activity but it is inhibited by the DNA replication checkpoint response. DDK and PP2A are identified in this study as the primary kinase
Malignant proliferation is the fundamental trait of tumor cells. The initiation of DNA replication represents a key process for cell proliferation, and has a marked impact on tumorigenesis and progression (19,21). The factors that promote DNA replication are organized in multiprotein complexes that coordinately help to recognize regions of origin, unwind DNA and promote replisome formation (21). The data in this study showed that SIX1 could modulate the expression of several genes related to DNA replication, thus accelerating G1 to S phase progression, promoting the proliferation of cervical cancer cells in vitro, and promoting the growth of cervical cancer in vivo.. The expression of SIX1 was closely correlated with the progression of cervical cancer as shown by our data. High levels of SIX1 expression were observed in almost all regions that developed intraepithelial neoplasia, suggesting that SIX1 might play an important role in tumorigenesis and progression of cervical cancer. Our data ...
Hiriyanna, KT and Ramakrishnan, T (1981) Dna-Replication In Mycobacterium-Tuberculosis H37 Rv. In: Indian Journal of Biochemistry & Biophysics, 18 (4). pp. 191-192. Full text not available from this repository. (Request a copy ...
Lien vers Pubmed [PMID] - 24130466. PLoS Comput. Biol. 2013;9(10):e1003233. Advances in genomic studies have led to significant progress in understanding the epigenetically controlled interplay between chromatin structure and nuclear functions. Epigenetic modifications were shown to play a key role in transcription regulation and genome activity during development and differentiation or in response to the environment. Paradoxically, the molecular mechanisms that regulate the initiation and the maintenance of the spatio-temporal replication program in higher eukaryotes, and in particular their links to epigenetic modifications, still remain elusive. By integrative analysis of the genome-wide distributions of thirteen epigenetic marks in the human cell line K562, at the 100 kb resolution of corresponding mean replication timing (MRT) data, we identify four major groups of chromatin marks with shared features. These states have different MRT, namely from early to late replicating, replication ...
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In semi-conservative DNA replication why does it happen that one of the new strands formed is discontinuous while other is continuous ...
WT cells under nutrient limitation exhibit two distinct regimes according to the Helmstetter-Cooper (HC) model of bacterial chromosome replication (Appendix Fig S9): In the fast growth regime (doubling time DT , single‐chromosome replication time, the "C‐period"), the C‐period is constant (at its minimal value) and the total DNA synthesis rate is determined by the replication initiation rate. In the slow growth regime (DT , C‐period), chromosome replication is limited by the replication fork elongation rate, which is in turn limited by the synthesis of nucleotides (DNA monomers) (Neidhart, 1996). Under LacZ OE, the DNA content increases (Figs 1F and EV3A and B). Since multiple chromosome equivalents per cell are observed in a single nucleoid complex (Fig EV3), the HC model of DNA replication may still be applicable with multiple replication forks per cell, provided that the C‐period , DT. The increase in DT under LacZ OE then implies that the C‐period would have to increase at least ...
DNA replication initiates from specific chromosomal sites called origins, and in the budding yeast Saccharomyces cerevisiae these sites are occupied by the origin recognition complex (ORC). Dbf4p is proposed to play a role in targeting the G1/S kinase Cdc7p to initiation complexes late in G1. We report that Dbf4p may also recruit Cdc5p to origin complexes. Cdc5p is a member of the Polo family of kinases that is required for the completion of mitosis. Cdc5p and Cdc7p each interact with a distinct domain of Dbf4p. cdc5-1 mutants have a plasmid maintenance defect that can be suppressed by the addition of multiple origins. cdc5-1 orc2-1 double mutants are synthetically lethal. Levels of Cdc5p were found to be cell cycle regulated and peaked in G2/M. These results suggest a role for Cdc5p and possibly Polo-like kinases at origin complexes.
BioAssay record AID 504364 submitted by NCGC: Validation screen for small molecules that induce DNA re-replication in SW480 colon adenocarcinoma cells.
Scientists at Cold Spring Harbor Laboratory (CSHL) have discovered how a protein long known to be an essential activator of DNA replication actually triggers this process in cells.. The protein, called DDK (for Ddf4-dependent protein kinase), is an enzyme that attaches phosphate molecules to other proteins to modify their activity. The CSHL team has found that DDK performs this operation, called phosphorylation, on a protein called Mcm4, specifically within a domain that acts as a built-in brake to prevent the DNA double helix from being unwound. The phosphorylation by DDK releases this brake, thus initiating the replication of unwound DNA strands.. "As DDK is often deregulated in human cancers, this new understanding of its role in DNA replication may help shape the development of new cancer therapies," explains CSHL President Bruce Stillman, Ph.D., who co-authored the study with colleague Yi-Jun Sheu, Ph.D. "Indeed recent studies have identified DDK inhibitors and they are now in clinical ...
The long-term objective of this proposal is to understand the cellular processes that regulate high-fidelity eukaryotic DNA replication. Low fidelity replicatio...
Double strand breaks in DNA are the initiating lesion for the translocation events that underlie the genome instability that causes cancer. However, the three dimensional organisation of the genetic material within the nucleus also influences the outcome of translocations because proximity of DNA strands increases the risk of their inappropriate joining. DNA replication has a dramatic effect both on break formation and on 3D nuclear organisation, but its roles in oncogenic translocations are undefined.. My group has a longstanding interest in DNA replication and its regulation. We have recently developed new techniques (Repli3C, Repli4C and Repli-C) to analyse the changes in genome organisation that accompany DNA replication. These methodologies are similar to the existing techniques of chromosome conformation capture (3C, 4C, Hi-C) but with the addition of EdU incorporation and affinity purification to enrich for newly replicated regions. In this project we will optimise and refine these ...
DNA replication. Computer artwork of a DNA (deoxyribonucleic acid) molecule replicating. DNA is composed of two strands twisted into a double helix. Before replication the strands separate from each other. Each strand then acts as a template for the formation of a new DNA molecule. This is known as semiconservative replication. DNA contains sections called genes, which encode the bodys genetic information. - Stock Image G110/0860
Franklin William Stahl studied DNA replication, bacteriophages, and genetic recombination in the US during the mid-twentieth and early twenty-first centuries. With his colleague Matthew Meselson, Stahl performed an experiment called the Meselson-Stahl experiment, which provided evidence for a process called semi-conservative DNA replication. Semi-conservative replication is a process in which each strand of a parental DNA double helix serves as a template for newly replicated daughter strands, so that one parental strand is conserved in every daughter double helix.. Format: Articles Subject: People ...