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Extrachromosomal DNA

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https://www.readbyqxmd.com/read/28615293/looping-out-mechanism-for-resolution-of-replicative-stress-at-telomeres
#1
Tianpeng Zhang, Zepeng Zhang, Feng Li, Qian Hu, Haiying Liu, Mengfan Tang, Wenbin Ma, Junjiu Huang, Zhou Songyang, Yikang Rong, Shichuan Zhang, Benjamin Pc Chen, Yong Zhao
Repetitive DNA is prone to replication fork stalling, which can lead to genome instability. Here, we find that replication fork stalling at telomeres leads to the formation of t-circle-tails, a new extrachromosomal structure that consists of circular telomeric DNA with a single-stranded tail. Structurally, the t-circle-tail resembles cyclized leading or lagging replication intermediates that are excised from the genome by topoisomerase II-mediated cleavage. We also show that the DNA damage repair machinery NHEJ is required for the formation of t-circle-tails and for the resolution of stalled replication forks, suggesting that NHEJ, which is normally constitutively suppressed at telomeres, is activated in the context of replication stress...
June 14, 2017: EMBO Reports
https://www.readbyqxmd.com/read/28608964/hbx-elevated-msl2-modulates-hbv-cccdna-through-inducing-degradation-of-apobec3b-to-enhance-hepatocarcinogenesis
#2
Yuen Gao, Jinyan Feng, Guang Yang, Shuqin Zhang, Yunxia Liu, Yanan Bu, Mingming Sun, Man Zhao, Fuquan Chen, Weiying Zhang, Lihong Ye, Xiaodong Zhang
Chronic hepatitis B virus (HBV) infection is a leading cause in the occurrence of hepatitis B, liver cirrhosis and liver cancer, in which nuclear HBV covalently closed circular DNA (cccDNA), the genomic form that templates viral transcription and sustains viral persistence, plays crucial roles. In the present study, we explored the hypothesis that HBV X protein (HBx)-elevated male-specific lethal 2 (MSL2) activated HBV replication via modulating cccDNA in hepatoma cells, leading to hepatocarcinogenesis. Immunohistochemical analysis revealed that the expression of MSL2 was positively associated with that of HBV and was increased in the liver tissues of HBV-transgenic mice and clinical HCC patients...
June 13, 2017: Hepatology: Official Journal of the American Association for the Study of Liver Diseases
https://www.readbyqxmd.com/read/28569776/hiv-integrase-inhibitor-elvitegravir-impairs-rag-functions-and-inhibits-v-d-j-recombination
#3
Mayilaadumveettil Nishana, Namrata M Nilavar, Rupa Kumari, Monica Pandey, Sathees C Raghavan
Integrase inhibitors are a class of antiretroviral drugs used for the treatment of AIDS that target HIV integrase, an enzyme responsible for integration of viral cDNA into host genome. RAG1, a critical enzyme involved in V(D)J recombination exhibits structural similarity to HIV integrase. We find that two integrase inhibitors, Raltegravir and Elvitegravir, interfered with the physiological functions of RAGs such as binding, cleavage and hairpin formation at the recombination signal sequence (RSS), though the effect of Raltegravir was limited...
June 1, 2017: Cell Death & Disease
https://www.readbyqxmd.com/read/28550083/normal-and-cancerous-tissues-release-extrachromosomal-circular-dna-eccdna-into-the-circulation
#4
Pankaj Kumar, Laura W Dillon, Yoshiyuki Shibata, Amir A Jazaeri, David R Jones, Anindya Dutta
Cell-free circulating linear DNA is being explored for noninvasive diagnosis and management of tumors and fetuses, the so-called liquid biopsy. Previously, we observed the presence of small extrachromosomal circular DNA (eccDNA), called microDNA, in the nuclei of mammalian tissues and cell lines. Now, we demonstrate that cell-free microDNA derived from uniquely mapping regions of the genome is detectable in plasma and serum from both mice and humans and that they are significantly longer (30%-60% >250 bases) than cell-free circulating linear DNA (∼150 bases)...
May 26, 2017: Molecular Cancer Research: MCR
https://www.readbyqxmd.com/read/28549174/phosphorylated-sirt1-associates-with-replication-origins-to-prevent-excess-replication-initiation-and-preserve-genomic-stability
#5
Koichi Utani, Haiqing Fu, Sang-Min Jang, Anna B Marks, Owen K Smith, Ya Zhang, Christophe E Redon, Noriaki Shimizu, Mirit I Aladjem
Chromatin structure affects DNA replication patterns, but the role of specific chromatin modifiers in regulating the replication process is yet unclear. We report that phosphorylation of the human SIRT1 deacetylase on Threonine 530 (T530-pSIRT1) modulates DNA synthesis. T530-pSIRT1 associates with replication origins and inhibits replication from a group of 'dormant' potential replication origins, which initiate replication only when cells are subject to replication stress. Although both active and dormant origins bind T530-pSIRT1, active origins are distinguished from dormant origins by their unique association with an open chromatin mark, histone H3 methylated on lysine 4...
May 26, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28429320/euglena-gracilis-genome-and-transcriptome-organelles-nuclear-genome-assembly-strategies-and-initial-features
#6
ThankGod Echezona Ebenezer, Mark Carrington, Michael Lebert, Steven Kelly, Mark C Field
Euglena gracilis is a major component of the aquatic ecosystem and together with closely related species, is ubiquitous worldwide. Euglenoids are an important group of protists, possessing a secondarily acquired plastid and are relatives to the Kinetoplastidae, which themselves have global impact as disease agents. To understand the biology of E. gracilis, as well as to provide further insight into the evolution and origins of the Kinetoplastidae, we embarked on sequencing the nuclear genome; the plastid and mitochondrial genomes are already in the public domain...
2017: Advances in Experimental Medicine and Biology
https://www.readbyqxmd.com/read/28411218/the-conjugative-relaxase-trwc-promotes-integration-of-foreign-dna-in-the-human-genome
#7
Coral González-Prieto, Richard Gabriel, Christoph Dehio, Manfred Schmidt, Matxalen Llosa
Bacterial conjugation is a mechanism of horizontal DNA transfer. The relaxase TrwC of the conjugative plasmid R388 cleaves one strand of the transferred DNA at the oriT, covalently attaches to it and leads the ssDNA into the recipient cell. In addition, TrwC catalyzes site-specific integration of the transferred DNA into its target sequence present in the genome of the recipient bacterium. Here, we report the analysis of the efficiency and specificity of the integrase activity of TrwC in human cells, using the Type IV Secretion System of the human pathogen Bartonella henselae to introduce relaxase-DNA complexes...
April 14, 2017: Applied and Environmental Microbiology
https://www.readbyqxmd.com/read/28406973/tre5-a-retrotransposition-profiling-reveals-putative-rna-polymerase-iii-transcription-complex-binding-sites-on-the-dictyostelium-extrachromosomal-rdna-element
#8
Thomas Spaller, Marco Groth, Gernot Glöckner, Thomas Winckler
The amoeba Dictyostelium discoideum has a haploid genome in which two thirds of the DNA encodes proteins. Consequently, the space available for selfish mobile elements to expand without excess damage to the host genome is limited. The non-long terminal repeat retrotransposon TRE5-A maintains an active population in the D. discoideum genome and apparently adapted to this gene-dense environment by targeting positions ~47 bp upstream of tRNA genes that are devoid of protein-coding regions. Because only ~24% of tRNA genes are associated with a TRE5-A element in the reference genome, we evaluated whether TRE5-A retrotransposition is limited to this subset of tRNA genes...
2017: PloS One
https://www.readbyqxmd.com/read/28403180/amplification-of-a-transgene-within-a-long-array-of-replication-origins-favors-higher-gene-expression-in-animal-cells
#9
Kiwamu Ohsaki, Yusuke Ohgaki, Noriaki Shimizu
Plasmids with both a mammalian replication initiation region (IR) and a matrix attachment region (MAR) are spontaneously amplified in transfected cells, and generate extrachromosomal double minute (DM) or chromosomal homogeneously staining region (HSR). We previously isolated the shortest core IR (G5) required for gene amplification. In this study, we ligated the G5 DNA to create direct or inverted repeats, mixed the repeats with an expression plasmid, and transfected the mixture into human COLO 320DM or hamster CHO DG44 cells...
2017: PloS One
https://www.readbyqxmd.com/read/28402891/brownian-ratchet-mechanism-for-faithful-segregation-of-low-copy-number-plasmids
#10
Longhua Hu, Anthony G Vecchiarelli, Kiyoshi Mizuuchi, Keir C Neuman, Jian Liu
Bacterial plasmids are extrachromosomal DNA that provides selective advantages for bacterial survival. Plasmid partitioning can be remarkably robust. For high-copy-number plasmids, diffusion ensures that both daughter cells inherit plasmids after cell division. In contrast, most low-copy-number plasmids need to be actively partitioned by a conserved tripartite ParA-type system. ParA is an ATPase that binds to chromosomal DNA; ParB is the stimulator of the ParA ATPase and specifically binds to the plasmid at a centromere-like site, parS...
April 11, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28366536/the-human-ctc1-stn1-ten1-complex-regulates-telomere-maintenance-in-alt-cancer-cells
#11
Chenhui Huang, Pingping Jia, Megan Chastain, Olga Shiva, Weihang Chai
Maintaining functional telomeres is important for long-term proliferation of cells. About 15% of cancer cells are telomerase-negative and activate the alternative-lengthening of telomeres (ALT) pathway to maintain their telomeres. Recent studies have shown that the human CTC1/STN1/TEN1 complex (CST) plays a multi-faceted role in telomere maintenance in telomerase-expressing cancer cells. However, the role of CST in telomere maintenance in ALT cells is unclear. Here, we report that human CST forms a functional complex localizing in the ALT-associated PML bodies (APBs) in ALT cells throughout the cell cycle...
June 15, 2017: Experimental Cell Research
https://www.readbyqxmd.com/read/28351714/evaluation-of-environmental-and-nutritional-factors-and-sua-gene-on-in%C3%A2-vitro-biofilm-formation-of-streptococcus-uberis-isolates
#12
Melina Vanesa Moliva, Florencia Cerioli, Elina Beatriz Reinoso
The pathogenesis of Streptococcus uberis is attributed to a combination of extracellular factors and properties such as adherence and biofilm formation. The aim of this work was to evaluate the influence of different factors, additives and bovine milk compounds on S. uberis biofilm formation, as the presence of the sua gene by PCR. Additionally, extracellular DNA and the effect of DNaseI were evaluated in the biofilms yielded. Optimal biofilm development was observed when the pH was adjusted to 7.0 and 37 °C...
March 27, 2017: Microbial Pathogenesis
https://www.readbyqxmd.com/read/28342852/effects-of-sub-culturing-on-genetic-and-physiological-parameters-in-different-beauveria-bassiana-isolates
#13
Naser Eivazian Kary, Zhila Alizadeh
Beauveria bassiana is a fungus which is widely used as a biological insecticide to control a number of economically important insect pests. Knowledge of the genetic diversity of the isolates, understanding the underlying nature of these evolutionary phenomena and finding appropriate and simple screening tools play an important role in developing effective biocontrol agents. Here, we monitored changes of electrophoretic karyotype of small molecules of extrachromosomal DNAs, presumably mitochondrial DNA or plasmids in several individual isolates of B...
March 23, 2017: Journal of Invertebrate Pathology
https://www.readbyqxmd.com/read/28324510/analysis-of-telomere-homologous-dna-with-different-conformations-using-2d-agarose-electrophoresis-and-in-gel-hybridization
#14
Zepeng Zhang, Qian Hu, Yong Zhao
In mammalian cells, in addition to double-stranded telomeric DNA at chromosome ends, extra telomere-homologous DNA is present that adopts different conformations, including single-stranded G- or C-rich DNA, extrachromosomal circular DNA (T-circle), and telomeric complex (T-complex) with an unidentified structure. The formation of such telomere-homologous DNA is closely related to telomeric DNA metabolism and chromosome end protection by telomeres. Conventional agarose gel electrophoresis is unable to separate DNA based on conformation...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28239156/cancer-genomics-ecdetect-hunts-extrachromosomal-dna
#15
Shimona Starling
No abstract text is available yet for this article.
April 2017: Nature Reviews. Genetics
https://www.readbyqxmd.com/read/28230082/tubz-filament-assembly-dynamics-requires-the-flexible-c-terminal-tail
#16
Maria E Fuentes-Pérez, Rafael Núñez-Ramírez, Alejandro Martín-González, David Juan-Rodríguez, Oscar Llorca, Fernando Moreno-Herrero, Maria A Oliva
Cytomotive filaments are essential for the spatial organization in cells, showing a dynamic behavior based on nucleotide hydrolysis. TubZ is a tubulin-like protein that functions in extrachromosomal DNA movement within bacteria. TubZ filaments grow in a helical fashion following treadmilling or dynamic instability, although the underlying mechanism is unclear. We have unraveled the molecular basis for filament assembly and dynamics combining electron and atomic force microscopy and biochemical analyses. Our findings suggest that GTP caps retain the filament helical structure and hydrolysis triggers filament stiffening upon disassembly...
February 23, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28213352/extrachromosomal-dna-amplifications-increase-oncogene-copy-number
#17
(no author information available yet)
Circular extrachromosomal DNA (ecDNA) amplifications promote tumor heterogeneity and evolution.
February 17, 2017: Cancer Discovery
https://www.readbyqxmd.com/read/28212615/molecular-pathways-underlying-inhibitory-effect-of-antimicrobial-peptide-nal-p-113-on-bacteria-biofilms-formation-of-porphyromonas-gingivalis-w83-by-dna-microarray
#18
Hong-Yan Wang, Li Lin, Li-Si Tan, Hui-Yuan Yu, Jya-Wei Cheng, Ya-Ping Pan
BACKGROUND: Wound-related infection remains a major challenge for health professionals. One disadvantage in conventional antibiotics is their inability to penetrate biofilms, the main protective strategy for bacteria to evade irradiation. Previously, we have shown that synthetic antimicrobial peptides could inhibit bacterial biofilms formation. RESULTS: In this study, we first delineated how Nal-P-113, a novel antimicrobial peptide, exerted its inhibitory effects on Porphyromonas gingivalis W83 biofilms formation at a low concentration...
February 17, 2017: BMC Microbiology
https://www.readbyqxmd.com/read/28212378/sequencing-the-extrachromosomal-circular-mobilome-reveals-retrotransposon-activity-in-plants
#19
Sophie Lanciano, Marie-Christine Carpentier, Christel Llauro, Edouard Jobet, Dagmara Robakowska-Hyzorek, Eric Lasserre, Alain Ghesquière, Olivier Panaud, Marie Mirouze
Retrotransposons are mobile genetic elements abundant in plant and animal genomes. While efficiently silenced by the epigenetic machinery, they can be reactivated upon stress or during development. Their level of transcription not reflecting their transposition ability, it is thus difficult to evaluate their contribution to the active mobilome. Here we applied a simple methodology based on the high throughput sequencing of extrachromosomal circular DNA (eccDNA) forms of active retrotransposons to characterize the repertoire of mobile retrotransposons in plants...
February 2017: PLoS Genetics
https://www.readbyqxmd.com/read/28178237/extrachromosomal-oncogene-amplification-drives-tumour-evolution-and-genetic-heterogeneity
#20
Kristen M Turner, Viraj Deshpande, Doruk Beyter, Tomoyuki Koga, Jessica Rusert, Catherine Lee, Bin Li, Karen Arden, Bing Ren, David A Nathanson, Harley I Kornblum, Michael D Taylor, Sharmeela Kaushal, Webster K Cavenee, Robert Wechsler-Reya, Frank B Furnari, Scott R Vandenberg, P Nagesh Rao, Geoffrey M Wahl, Vineet Bafna, Paul S Mischel
Human cells have twenty-three pairs of chromosomes. In cancer, however, genes can be amplified in chromosomes or in circular extrachromosomal DNA (ecDNA), although the frequency and functional importance of ecDNA are not understood. We performed whole-genome sequencing, structural modelling and cytogenetic analyses of 17 different cancer types, including analysis of the structure and function of chromosomes during metaphase of 2,572 dividing cells, and developed a software package called ECdetect to conduct unbiased, integrated ecDNA detection and analysis...
March 2, 2017: Nature
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