scholarly journals Transcription activity contributes to the firing of non-constitutive origins in Trypanosoma brucei

2018 ◽  
Author(s):  
Marcelo S. da Silva ◽  
Gustavo R. Cayres-Silva ◽  
Marcela O. Vitarelli ◽  
Paula A. Marin ◽  
Priscila M. Hiraiwa ◽  
...  
Keyword(s):  
Genomic Instability ◽  
Trypanosoma Brucei ◽  
Computational Analysis ◽  
S Phase ◽  
Phase Duration ◽  
Biological Assays ◽  
Transcription Activity ◽  
Dna And Rna ◽  
Polycistronic Transcription ◽  
The World

ABSTRACTThe cosynthesis of DNA and RNA potentially generates conflicts between replication and transcription, which can lead to genomic instability. In trypanosomatids, eukaryotic parasites that perform polycistronic transcription, this phenomenon and its consequences have not yet been investigated. Here, using equations and computational analysis we demonstrated that the number of constitutive origins mapped in the Trypanosoma brucei genome is close to the minimum required to complete replication within S phase duration. However, taking into account the location of these origins in the genome, the replication in due time becomes virtually impossible, making it necessary to activate non-constitutive origins. Moreover, computational and biological assays pointed to transcription being responsible for activating non-constitutive origins. Together, our results suggest that transcription action through conflicts with replication contributes to the firing of non-constitutive origins, maintaining the robustness of S phase duration. The usage of this entire pool of origins seems to be of paramount importance for the survival of this parasite that infects million people around the world since it contributes to the maintenance of the replication of its DNA.

scholarly journals Transcription activity contributes to the firing of non-constitutive origins in African trypanosomes helping to maintain robustness in S-phase duration

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Marcelo S. da Silva ◽  
Gustavo R. Cayres-Silva ◽  
Marcela O. Vitarelli ◽  
Paula A. Marin ◽  
Priscila M. Hiraiwa ◽  
...  
Keyword(s):  
Dna Replication ◽  
Mechanistic Model ◽  
S Phase ◽  
Dna Lesions ◽  
Phase Duration ◽  
African Trypanosomes ◽  
Transcription Activity ◽  
Dna And Rna ◽  
Polycistronic Transcription ◽  
Dna Combing

AbstractThe co-synthesis of DNA and RNA potentially generates conflicts between replication and transcription, which can lead to genomic instability. In trypanosomatids, eukaryotic parasites that perform polycistronic transcription, this phenomenon and its consequences are still little studied. Here, we showed that the number of constitutive origins mapped in the Trypanosoma brucei genome is less than the minimum required to complete replication within S-phase duration. By the development of a mechanistic model of DNA replication considering replication-transcription conflicts and using immunofluorescence assays and DNA combing approaches, we demonstrated that the activation of non-constitutive (backup) origins are indispensable for replication to be completed within S-phase period. Together, our findings suggest that transcription activity during S phase generates R-loops, which contributes to the emergence of DNA lesions, leading to the firing of backup origins that help maintain robustness in S-phase duration. The usage of this increased pool of origins, contributing to the maintenance of DNA replication, seems to be of paramount importance for the survival of this parasite that affects million people around the world.

scholarly journals The duration of the active phase on surge-type glaciers: contrasts between Svalbard and other regions

1991 ◽  
Vol 37 (127) ◽  
pp. 388-400 ◽  
Author(s):  
Julian A. Dowdeswell ◽  
Gordon S. Hamilton ◽  
Jon Ove Hagen
Keyword(s):  
Time Series ◽  
North America ◽  
Active Phase ◽  
Aerial Photographs ◽  
Polar Ice ◽  
Phase Duration ◽  
Field Surveys ◽  
The World ◽  
Glacier Surges ◽  
Fast Motion

AbstractMany glaciers in Svalbard and in other glacierized areas of the world are known to surge. However, the time series of observations required to assess the duration of fast motion is very restricted. Data on active-phase duration in Svalbard come from aerial photographs, satellite imagery, field surveys and airborne reconnaissance. Evidence on surge duration is available for eight Svalbard ice masses varying from 3 to 1250 km2. Worldwide, active-phase duration is recorded for less than 50 glaciers. Few observations are available on high polar ice masses. The duration of the active phase is significantly longer for Svalbard glaciers than for surge-type glaciers in other areas from which data are available. In Svalbard, the active phase may last from 3 to 10 years. By contrast, a surge duration of 1–2 years is more typical of ice masses in northwest North America, Iceland and the Pamirs. Ice velocities during the protracted active phase on Svalbard glaciers are considerably lower than those for many surge-type glaciers in these other regions. Mass is transferred down-glacier more slowly but over a considerably longer period. Svalbard surge-type glaciers do not exhibit the very abrupt termination of the active phase, over periods of a few days, observed for several Alaskan glaciers. The duration of the active phase in Svalbard is not dependent on parameters related to glacier size. The quiescent phase is also relatively long (50–500 years) for Svalbard ice masses. Detailed field monitoring of changing basal conditions through the surge cycle is required from surge-type glaciers in Svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago, which may also typify other high polar ice masses. The finding that surge behaviour, in the form of active-phase duration, shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges.

scholarly journals Molecular and Biological Characterisation of Turnip mosaic virus Isolates Infecting Poppy (Papaver somniferum and P. rhoeas) in Slovakia

Viruses ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 430 ◽  
Author(s):  
Miroslav Glasa ◽  
Katarína Šoltys ◽  
Lukáš Predajňa ◽  
Nina Sihelská ◽  
Slavomíra Nováková ◽  
...  
Keyword(s):  
Mosaic Virus ◽  
Phylogenetic Analyses ◽  
Molecular Data ◽  
Turnip Mosaic Virus ◽  
Biological Assays ◽  
Genetic Complexity ◽  
The World ◽  
History Of ◽  
Virus Isolates

In recent years, the accumulated molecular data of Turnip mosaic virus (TuMV) isolates from various hosts originating from different parts of the world considerably helped to understand the genetic complexity and evolutionary history of the virus. In this work, four complete TuMV genomes (HC9, PK1, MS04, MS15) were characterised from naturally infected cultivated and wild-growing Papaver spp., hosts from which only very scarce data were available previously. Phylogenetic analyses showed the affiliation of Slovak Papaver isolates to the world-B and basal-B groups. The PK1 isolate showed a novel intra-lineage recombination pattern, further confirming the important role of recombination in the shaping of TuMV genetic diversity. Biological assays indicated that the intensity of symptoms in experimentally inoculated oilseed poppy are correlated to TuMV accumulation level in leaves. This is the first report of TuMV in poppy plants in Slovakia.

scholarly journals Measurement of S-phase duration of adult stem cells in the flatwormMacrostomum lignanoby double replication labelling and quantitative colocalization analysis

2012 ◽  
Vol 36 (12) ◽  
pp. 1251-1259 ◽  
Author(s):  
Freija Verdoodt ◽  
Maxime Willems ◽  
Ineke Dhondt ◽  
Wouter Houthoofd ◽  
Wim Bert ◽  
...  
Keyword(s):  
Stem Cells ◽  
Adult Stem Cells ◽  
S Phase ◽  
Phase Duration

scholarly journals Cyclin Kinase-independent role of p21CDKN1A in the promotion of nascent DNA elongation in unstressed cells

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Sabrina F Mansilla ◽  
Agustina P Bertolin ◽  
Valérie Bergoglio ◽  
Marie-Jeanne Pillaire ◽  
Marina A González Besteiro ◽  
...  
Keyword(s):  
Genomic Instability ◽  
Genomic Stability ◽  
S Phase ◽  
Fragile Sites ◽  
Dna Lesions ◽  
Cdk Inhibitor ◽  
Cyclin Dependent Kinase ◽  
Independent Manner ◽  
Genomic Regions

The levels of the cyclin-dependent kinase (CDK) inhibitor p21 are low in S phase and insufficient to inhibit CDKs. We show here that endogenous p21, instead of being residual, it is functional and necessary to preserve the genomic stability of unstressed cells. p21depletion slows down nascent DNA elongation, triggers permanent replication defects and promotes the instability of hard-to-replicate genomic regions, namely common fragile sites (CFS). The p21’s PCNA interacting region (PIR), and not its CDK binding domain, is needed to prevent the replication defects and the genomic instability caused by p21 depletion. The alternative polymerase kappa is accountable for such defects as they were not observed after simultaneous depletion of both p21 and polymerase kappa. Hence, in CDK-independent manner, endogenous p21 prevents a type of genomic instability which is not triggered by endogenous DNA lesions but by a dysregulation in the DNA polymerase choice during genomic DNA synthesis.

scholarly journals Replication fork rate and origin activation during the S phase of Saccharomyces cerevisiae.

1980 ◽  
Vol 85 (1) ◽  
pp. 108-115 ◽  
Author(s):  
C J Rivin ◽  
W L Fangman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cycle Length ◽  
Replication Fork ◽  
Nitrogen Sources ◽  
S Phase ◽  
Phase Duration ◽  
Yeast Saccharomyces Cerevisiae ◽  
Origin Activation ◽  
Cell Cycle Length

When the growth rate of the yeast Saccharomyces cerevisiae is limited with various nitrogen sources, the duration of the S phase is proportional to cell cycle length over a fourfold range of growth rates (C.J. Rivin and W. L. Fangman, 1980, J. Cell Biol. 85:96-107). Molecular parameters of the S phases of these cells were examined by DNA fiber autoradiography. Changes in replication fork rate account completely for the changes in S-phase duration. No changes in origin-to-origin distances were detected. In addition, it was found that while most adjacent replication origins are activated within a few minutes of each other, new activations occur throughout the S phase.

A gene from the variant surface glycoprotein expression site encodes one of several transmembrane adenylate cyclases located on the flagellum of Trypanosoma brucei

1992 ◽  
Vol 12 (3) ◽  
pp. 1218-1225
Author(s):  
P Paindavoine ◽  
S Rolin ◽  
S Van Assel ◽  
M Geuskens ◽  
J C Jauniaux ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Trypanosoma Brucei ◽  
Membrane Fraction ◽  
Transcription Unit ◽  
Bloodstream Form ◽  
Surface Glycoprotein ◽  
Yeast Cells ◽  
Variant Surface Glycoprotein ◽  
Polycistronic Transcription ◽  
Expression Site

The bloodstream form of Trypanosoma brucei contains transcripts of at least four genes showing partial sequence homology to the genes for eucaryotic adenylate and guanylate cyclases (S. Alexandre, P. Paindavoine, P. Tebabi, A. Pays, S. Halleux, M. Steinert, and E. Pays, Mol. Biochem. Parasitol. 43:279-288, 1990). One of these genes, termed ESAG 4, belongs to the polycistronic transcription unit of the variant surface glycoprotein (VSG) gene. Whereas ESAG 4 is transcribed only in the bloodstream form of the parasite, the three other genes, GRESAG 4.1, 4.2, and 4.3, are also expressed in procyclic (insect) forms. These genes differ primarily in a region presumed to encode a large extracellular domain. We show here that ESAG 4-related glycoproteins of about 150 kDa can be found in the trypanosome membrane, that they are detected, by light and electron gold immunocytochemistry, only at the surface of the flagellum, and that the products of at least two of these genes, ESAG 4 and GRESAG 4.1, can complement a Saccharomyces cerevisiae mutant for adenylate cyclase. The recombinant cyclases are associated with the yeast membrane fraction and differ with respect to their activation by calcium: while the GRESAG 4.1 and yeast cyclases are inhibited by calcium, the ESAG 4 cyclase is stimulated. ESAG 4 thus most probably encodes the calcium-activated cyclase that has been found to be expressed only in the bloodstream form of T. brucei (S. Rolin, S. Halleux, J. Van Sande, J. E. Dumont, E. Pays, and M. Steinert. Exp. Parasitol. 71:350-352, 1990). Our data suggest that the trypanosome cyclases are not properly regulated in yeast cells.

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