DNA replication

The cell reproduction of Mycoplasma capricolum was studied. The velocity of DNA replication fork progres- sion was about 6 kb/min, which is 10 times slower than that of Escherichia coli. The time required for one round of DNA replication accorded with the doubling time. The origin/terminus ratio was 2.0. M. capricolum cell morphology was classified into two types, rod and

Diethylhexylphthalate (DEHP) and diisono-nylphthalate (DINP) are plasticizers with many impor-tant commercial, industrial and medical applications. However, both DEHP and DINP are rodent peroxisome proliferators (PPs), a class of compounds that cause rodent ...

The expression of proliferating cell nuclear antigen (PCNA) was studied in human papillomavirus (HPV)-infected, benign and malignant lesions of the genital tract and larynx using immunocytochemical staining of formalin-fixed clinical specimens. We observed the induction of PCNA in squamous carcinomas and adenocarcinomas, as has been demonstrated with other malignancies. In addition, the differentiated keratinocytes of the upper spinous cells and granulocytes in condylomata acuminata and low-grade intraepithelial neoplasias showed a consistent induction of PCNA compared with the normal squamous epithelium, in which only some of the parabasal and basal cells were positive. This reactivation of PCNA synthesis correlated with the presence of high copy numbers of HPV DNA and was independent of the oncogenic risk potential of the infecting HPV genotype. We postulate that HPV gene products induce the expression of PCNA and other components of the host DNA replication machinery in different...

Many aspects of the mitotic cycle can take place independently in syncytial Drosophila embryos. Embryos from females homozygous for the mutation gnu undergo rounds of DNA synthesis without nuclear division to produce giant nuclei, and at the same time show many cycles of centrosome replication (Freeman et al. 1986). S phase can be inhibited in wild-type Drosophila embryos by injecting aphidicolin, in which case not only do centrosomes replicate, but chromosomes continue to condense and decondense, the nuclear envelope undergoes cycles of breakdown and reformation, and cycles of budding activity continue at the cortex of the embryo (Raff and Glover, 1988). If aphidicolin is injected when nuclei are in the interior of the embryo, centrosomes dissociate from the nuclei and can migrate to the cortex. Pole cells without nuclei then form around those centrosomes that reach the posterior pole (Raff and Glover, 1989); the centrosomes presumably must interact with polar granules, the materna...

The adeno-associated virus 2 (AAV) genome is a single-stranded DNA which contains the inverted terminal repeats (ITRs) of 145 nucleotides. The terminal 125 nucleotides of each ITR form palindromic hairpin structures that serve as primers for AAV DNA replication. These hairpin structures also play a crucial role in the integration, as well as the rescue, of the proviral genome from latently-infected cells, or from the recombinant AAV plasmids. However, the ITRs also contain an additional domain, designated the D-sequence, a 20-nucleotide stretch that is not involved in the formation of hairpins. In order to examine the role of the D-sequence in viral DNA rescue and replication, a number of recombinant AAV plasmids were constructed which contained deletions/substitutions in different regions of the ITRs. The results presented here reveal the existence of additional sequences, other than the hairpin structures, which serve as primers for AAV DNA replication. The results also show that whereas the hairpin structures are sufficient for excision and replication of the viral DNA, the D-sequence is crucial for the high efficiency of rescue and replication of the AAV genome.

Information transfer is fundamental to all life forms. In the third domain of life, the archaea, many of the genes functioning in these processes are similar to their eukaryotic counterparts, including DNA replication and repair, basal transcription, and translation genes, while many transcriptional regulators and the overall genome structure are more bacterial-like. Among halophilic (salt-loving) archaea, the genomes commonly include extrachromosomal elements, many of which are large megaplasmids or minichromosomes. With the sequencing of genomes representing ten different genera of halophilic archaea and the availability of genetic systems in two diverse models, Halobacterium sp. NRC-1 and Haloferax volcanii, a large number of genes have now been annotated, classified, and studied. Here, we review the comparative genomic, genetic, and biochemical work primarily aimed at the information transfer system of halophilic archaea, highlighting gene conservation and differences in the chromosomes and the large extrachromosomal elements among these organisms.Copyright © 2010 Elsevier Inc. All rights reserved.

The expression of mitochondrial components is controlled by an intricate interplay between nuclear transcription factors and retrograde signaling from mitochondria. The role of mitochondrial DNA (mtDNA) and mtDNA-encoded proteins in mitochondrial biogenesis is, however, poorly understood and thus far has mainly been studied in transformed cell lines. We treated primary human fibroblasts with ethidium bromide (EtBr) or chloramphenicol for six weeks to inhibit mtDNA replication or mitochondrial protein synthesis, respectively, and investigated how the cells recovered from these insults two weeks after removal of the drugs. Although cellular growth and mitochondrial gene expression were severely impaired after both inhibitor treatments we observed marked differences in mitochondrial structure,membrane potential, glycolysis, gene expression, and redox status between fibroblasts treated with EtBr and chloramphenicol. Following removal of the drugs we further detected clear differences in expression of both mtDNA-encoded genes and nuclear transcription factors that control mitochondrial biogenesis, suggesting that the cells possess different compensatory mechanisms to recover from drug-induced mitochondrial dysfunction. Our data reveal new aspects of the interplay between mitochondrial retrograde signaling and the expression of nuclear regulators of mitochondrial biogenesis, a process with direct relevance to mitochondrial diseases and chloramphenicol toxicity in humans.

Life depends on double-stranded DNA unwinding and separating into single strands that can be copied for cell division. St. Jude Children's Research Hospital scientists have determined at atomic resolution the structure of machinery that drives the process. [19] Researchers at Delft University of Technology, in collaboration with colleagues at the Autonomous University of Madrid, have created an artificial DNA blueprint for the replication of DNA in a cell-like structure. [18] An LMU team now reveals the inner workings of a molecular motor made of proteins which packs and unpacks DNA. [17] Chemist Ivan Huc finds the inspiration for his work in the molecular principles that underlie biological systems. [16] What makes particles self-assemble into complex biological structures? [15] Scientists from Moscow State University (MSU) working with an international team of researchers have identified the structure of one of the key regions of telomerase-a so-called "cellular immortality" ribonucleoprotein. [14] Researchers from Tokyo Metropolitan University used a light-sensitive iridium-palladium catalyst to make "sequential" polymers, using visible light to change how building blocks are combined into polymer chains. [13] Researchers have fused living and non-living cells for the first time in a way that allows them to work together, paving the way for new applications. [12] UZH researchers have discovered a previously unknown way in which proteins interact with one another and cells organize themselves. [11] Dr Martin Sweatman from the University of Edinburgh's School of Engineering has discovered a simple physical principle that might explain how life started on Earth. [10] Nearly 75 years ago, Nobel Prize-winning physicist Erwin Schrödinger wondered if the mysterious world of quantum mechanics played a role in biology. A recent finding by Northwestern University's Prem Kumar adds further evidence that the answer might be yes. [9]

More or less well-defined mixtures of antibiotics used in aquacultures may be distributed in the aquatic environment. Therefore, a systematic mixture ecotoxicity study was performed with the aquaculture antibiotics oxytetracycline, oxolinic acid, erythromycin, florfenicol, and flumequine. Test organisms were freshwater algae (Pseudokirchneriella subcapitata), activated sludge microorganisms, and luminescent bacteria (Vibrio fischeri). Design and statistical analysis of test results were based on isobolographic analysis. Synergistic effects were observed when combinations of erythromycin and oxytetracycline were tested on activated sludge microorganisms, and in these cases model predictions indicate independent action on the different bacterial species in the sludge. As predicted from the modes of action, concentration addition was evident when flumequine and oxolinic acid were mixed and tested on sludge bacteria. In the algae test, the combined toxicity of antibiotics could not be predicted based on knowledge of the modes of action of the individual compounds. Independent of the test species, our results gave examples of combined effects that were higher than predicted based on the assumption of concentration addition. This result underlines the need to consider the effects of mixtures of antibiotics on environmental organisms. The isobolographic method appears to be a suitable tool for this purpose, particularly for well-defined mixtures with few substances.

Heather Dewey-Hagborg reconstructs the plausible faces of the carriers of these macromolecules, which she identifies through biological analysis and cross-checks with the assumptions underlying contemporary forensics. It’s her series of portraits of strangers, Stranger Visions (2012-13), which has more widely brought to the public attention the practice of the artist and biohacker, and her critique of a genetic determinism that, although based on the latest technologies, is no less than the last in a long line of practices for classifying human beings into categories for the least contingent. While large-scale DNA collection in criminal investigations hit the headlines of the European press and the double helix of the DNA emoji has just been reoriented after igniting the scientific community, the New York artist gives us the ins and outs of her last two projects: Probably Chelsea (2017) and T3511 (2018).

La réplication consiste à copier et de distribuer un ensemble de données et d’objets d’une base de données vers une autre, puis de synchroniser ces bases de données afin de préserver leur cohérence. Les deux bases de données peuvent être stockées à des emplacements distincts.  Il existe sous SQL Server plusieurs types de réplication : Instantanée  (snapshot), transactionnelle, Fusion.
Le cas pratique traité dans ce document est celui de la réplication fusion qui démarre généralement avec une copie instantanée des objets de la base de donnée de publication.