scholarly journals Novel PMS1 Alleles Preferentially Affect the Repair of Primer Strand Loops during DNA Replication

2005 ◽  
Vol 25 (21) ◽  
pp. 9221-9231 ◽  
Author(s):  
Naz Erdeniz ◽  
Sandra Dudley ◽  
Regan Gealy ◽  
Sue Jinks-Robertson ◽  
R. Michael Liskay
Keyword(s):  
Mammalian Cells ◽  
Current View ◽  
Dna Mismatch ◽  
Template Strand ◽  
Repeat Sequences ◽  
Mutation Avoidance ◽  
Mismatch Recognition ◽  
Lagging Strand ◽  
Simple Sequence ◽  
Polymerase Slippage

ABSTRACT Null mutations in DNA mismatch repair (MMR) genes elevate both base substitutions and insertions/deletions in simple sequence repeats. Data suggest that during replication of simple repeat sequences, polymerase slippage can generate single-strand loops on either the primer or template strand that are subsequently processed by the MMR machinery to prevent insertions and deletions, respectively. In the budding yeast Saccharomyces cerevisiae and mammalian cells, MMR appears to be more efficient at repairing mispairs comprised of loops on the template strand compared to loops on the primer strand. We identified two novel yeast pms1 alleles, pms1-G882E and pms1-H888R, which confer a strong defect in the repair of “primer strand” loops, while maintaining efficient repair of “template strand” loops. Furthermore, these alleles appear to affect equally the repair of 1-nucleotide primer strand loops during both leading- and lagging-strand replication. Interestingly, both pms1 mutants are proficient in the repair of 1-nucleotide loop mispairs in heteroduplex DNA generated during meiotic recombination. Our results suggest that the inherent inefficiency of primer strand loop repair is not simply a mismatch recognition problem but also involves Pms1 and other proteins that are presumed to function downstream of mismatch recognition, such as Mlh1. In addition, the findings reinforce the current view that during mutation avoidance, MMR is associated with the replication apparatus.

scholarly journals Telomerase Inhibition for Killing Cancer Cells

2019 ◽  
Author(s):  
Mahnoor Patel
Keyword(s):  
Cancer Cells ◽  
Dna Polymerase ◽  
Human Cells ◽  
Telomerase Inhibition ◽  
Template Strand ◽  
Repeat Sequences ◽  
Hayflick Limit ◽  
Upper Limit ◽  
A Cell ◽  
Lagging Strand

There is an upper limit to the number of times a cell can divide before it stops growing and enters a phase which is called senescence. For human embryonic diploid fibroblasts, the Hayflick limit is about 60 doublings. This limit is related to the end-replication problem faced by DNA polymerase as it moves along a template strand synthesizing a new strand. DNA polymerase must initiate synthesis from an RNA primer and it synthesizes a new strand beginning with the primers 3 end. The need for the RNA primer means that the DNA polymerase cannot replicate the very 5 end of the lagging strand because the primer occupies the last few bases of the template strand. As a consequence, the DNA of a chromosome shortens by 50-100 nucleotides each time the chromosome replicates. Eukaryotic chromosomes have telomeres at their ends, which are long sections made up of a repeat sequences, TTAGGG in human cells. These sequences protect the ends of the chromosomes, thus preventing the chromosomes from interacting with each other. Telomeres are eroded with each division until they no longer function properly, with catastrophic results for the cell.

scholarly journals Accumulation of Single-Stranded DNA and Destabilization of Telomeric Repeats in Yeast Mutant Strains Carrying a Deletion of RAD27

1999 ◽  
Vol 19 (6) ◽  
pp. 4143-4152 ◽  
Author(s):  
Julie Parenteau ◽  
Raymund J. Wellinger
Keyword(s):  
Growth Arrest ◽  
Dna Lesions ◽  
Restrictive Temperature ◽  
Telomeric Dna ◽  
Single Stranded Dna ◽  
Template Strand ◽  
Okazaki Fragments ◽  
A Cell ◽  
Lagging Strand

ABSTRACT The Saccharomyces cerevisiae RAD27 gene encodes the yeast homologue of the mammalian FEN-1 nuclease, a protein that is thought to be involved in the processing of Okazaki fragments during DNA lagging-strand synthesis. One of the predicted DNA lesions occurring in rad27 strains is the presence of single-stranded DNA of the template strand for lagging-strand synthesis. We examined this prediction by analyzing the terminal DNA structures generated during telomere replication in rad27strains. The lengths of the telomeric repeat tracts were found to be destabilized in rad27 strains, indicating that naturally occurring direct repeats are subject to tract expansions and contractions in such strains. Furthermore, abnormally high levels of single-stranded DNA of the templating strand for lagging-strand synthesis were observed in rad27 cells. Overexpression of Dna2p in wild-type cells also yielded single-stranded DNA regions on telomeric DNA and caused a cell growth arrest phenotype virtually identical to that seen for rad27 cells grown at the restrictive temperature. Furthermore, overexpression of the yeast exonuclease Exo1p alleviated the growth arrest induced by both conditions, overexpression of Dna2p and incubation of rad27cells at 37°C. However, the telomere heterogeneity and the appearance of single-stranded DNA are not prevented by the overexpression of Exo1p in these strains, suggesting that this nuclease is not simply redundant with Rad27p. Our data thus provide in vivo evidence for the types of DNA lesions predicted to occur when lagging-strand synthesis is deficient and suggest that Dna2p and Rad27p collaborate in the processing of Okazaki fragments.

Escherichia coli and colorectal cancer: Unfolding the enigmatic relationship

2021 ◽  
Vol 22 ◽  
Author(s):  
Rogayeh Nouri ◽  
Alka Hasani ◽  
Kourosh Masnadi Shirazi ◽  
Mohammad Reza Aliand ◽  
Bita Sepehri ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Escherichia Coli ◽  
Mammalian Cells ◽  
Chromosomal Rearrangements ◽  
Current Evidence ◽  
Dna Breaks ◽  
Colon Cells ◽  
E Coli ◽  
Dna Mismatch ◽  
Double Strand Dna Breaks

: Colorectal cancer (CRC) is one of the deadliest cancers in the world. Specific strains of intestinal Escherichia coli (E. coli) may influence the initiation and development of CRC by exploiting virulence factors and inflammatory pathways. Mucosa-associated E. coli strains are more prevalent in CRC biopsies in comparison to healthy controls. Moreover, these strains can survive and replicate within macrophages and induce a pro-inflammatory response. Chronic exposure to inflammatory mediators can lead to increased cell proliferation and cancer. Production of colobactin toxin by the majority of mucosa-associated E. coli isolated from CRC patients is another notable finding. Colibactin-producing E. coli strains, in particular, induce double-strand DNA breaks, stop the cell cycle, involve in chromosomal rearrangements of mammalian cells and are implicated in carcinogenic effects in animal models. Moreover, some enteropathogenic E. coli (EPEC) strains are able to survive and replicate in colon cells as chronic intracellular pathogens and may promote susceptibility to CRC by downregulation of DNA Mismatch Repair (MMR) proteins. In this review, we discuss current evidence and focus on the mechanisms by which E. coli can influence the development of CRC.

Determinants of DNA Mismatch Recognition within the Polymerase Domain of the Klenow Fragment†

Biochemistry ◽  
2002 ◽  
Vol 41 (3) ◽  
pp. 713-722 ◽  
Author(s):  
Elizabeth H. Z. Thompson ◽  
Michael F. Bailey ◽  
Edwin J. C. van der Schans ◽  
Catherine M. Joyce ◽  
David P. Millar
Keyword(s):  
Klenow Fragment ◽  
Dna Mismatch ◽  
Polymerase Domain ◽  
Mismatch Recognition

scholarly journals Phosphorylation of PCNA by EGFR inhibits mismatch repair and promotes misincorporation during DNA synthesis

2015 ◽  
Vol 112 (18) ◽  
pp. 5667-5672 ◽  
Author(s):  
Janice Ortega ◽  
Jessie Y. Li ◽  
Sanghee Lee ◽  
Dan Tong ◽  
Liya Gu ◽  
...  
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Mismatch Repair ◽  
Posttranslational Modifications ◽  
Growth Factor Receptor ◽  
Nuclear Antigen ◽  
Dna Mismatch ◽  
Epidermal Growth ◽  
Mismatch Recognition ◽  
Proliferating Cell

Proliferating cell nuclear antigen (PCNA) plays essential roles in eukaryotic cells during DNA replication, DNA mismatch repair (MMR), and other events at the replication fork. Earlier studies show that PCNA is regulated by posttranslational modifications, including phosphorylation of tyrosine 211 (Y211) by the epidermal growth factor receptor (EGFR). However, the functional significance of Y211-phosphorylated PCNA remains unknown. Here, we show that PCNA phosphorylation by EGFR alters its interaction with mismatch-recognition proteins MutSα and MutSβ and interferes with PCNA-dependent activation of MutLα endonuclease, thereby inhibiting MMR at the initiation step. Evidence is also provided that Y211-phosphorylated PCNA induces nucleotide misincorporation during DNA synthesis. These findings reveal a novel mechanism by which Y211-phosphorylated PCNA promotes cancer development and progression via facilitating error-prone DNA replication and suppressing the MMR function.

DNA Mismatch Binding and Incision at Modified Guanine Bases by Extracts of Mammalian Cells: Implications for Tolerance to DNA Methylation Damage

Biochemistry ◽  
1994 ◽  
Vol 33 (16) ◽  
pp. 4787-4793 ◽  
Author(s):  
Shaun Griffin ◽  
Pauline Branch ◽  
Yao-Zhong Xu ◽  
Peter Karran
Keyword(s):  
Dna Methylation ◽  
Mammalian Cells ◽  
Dna Mismatch

Dynamics of autophagosome formation: a pulse and a sequence of waves

2014 ◽  
Vol 42 (5) ◽  
pp. 1389-1395 ◽  
Author(s):  
Nicholas T. Ktistakis ◽  
Eleftherios Karanasios ◽  
Maria Manifava
Keyword(s):  
Mammalian Cells ◽  
De Novo ◽  
Stress Conditions ◽  
Present Review ◽  
Eukaryotic Cells ◽  
Current View ◽  
Protein Assemblies ◽  
Autophagosome Formation ◽  
Flat Membrane ◽  
A Current

Autophagosomes form in eukaryotic cells in response to starvation or to other stress conditions brought about by the unwanted presence in the cytosol of pathogens, damaged organelles or aggregated protein assemblies. The uniqueness of autophagosomes is that they form de novo and that they are the only double-membraned vesicles known in cells, having arisen from flat membrane sheets which have expanded and self-closed. The various steps describing their formation as well as most of the protein and lipid components involved have been identified. Furthermore, the hierarchical relationships among the components are well documented, and the mechanistic rationale for some of these hierarchies has been revealed. In the present review, we try to provide a current view of the process of autophagosome formation in mammalian cells, emphasizing along the way gaps in our knowledge that need additional work.

scholarly journals In Vitro Reconstitution of the End Replication Problem

2001 ◽  
Vol 21 (17) ◽  
pp. 5753-5766 ◽  
Author(s):  
Rieko Ohki ◽  
Toshiki Tsurimoto ◽  
Fuyuki Ishikawa
Keyword(s):  
Mammalian Cells ◽  
Simian Virus 40 ◽  
Simian Virus ◽  
Telomere Attrition ◽  
Linear Dna ◽  
In Vitro Reconstitution ◽  
Biochemical Approach ◽  
Optimized Conditions ◽  
Lagging Strand

ABSTRACT The end replication problem hypothesis proposes that the ends of linear DNA cannot be replicated completely during lagging strand DNA synthesis. Although the idea has been widely accepted for explaining telomere attrition during cell proliferation, it has never been directly demonstrated. In order to take a biochemical approach to understand how linear DNA ends are replicated, we have established a novel in vitro linear simian virus 40 DNA replication system. In this system, terminally biotin-labeled linear DNAs are conjugated to avidin-coated beads and subjected to replication reactions. Linear DNA was efficiently replicated under optimized conditions, and replication products that had replicated using the original DNA templates were specifically analyzed by purifying bead-bound replication products. By exploiting this system, we showed that while the leading strand is completely synthesized to the end, lagging strand synthesis is gradually halted in the terminal ∼500-bp region, leaving 3′ overhangs. This result is consistent with observations in telomerase-negative mammalian cells and formally demonstrates the end replication problem. This study provides a basis for studying the details of telomere replication.

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