Search results for "Biochemistry & Molecular Biology"
showing 10 items of 431 documents
Nucleoside Analogue Mutagenesis of a Single-Stranded DNA Virus: Evolution and Resistance
2012
ABSTRACT It has been well established that chemical mutagenesis has adverse fitness effects in RNA viruses, often leading to population extinction. This is mainly a consequence of the high RNA virus spontaneous mutation rates, which situate them close to the extinction threshold. Single-stranded DNA viruses are the fastest-mutating DNA-based systems, with per-nucleotide mutation rates close to those of some RNA viruses, but chemical mutagenesis has been much less studied in this type of viruses. Here, we serially passaged bacteriophage ϕX174 in the presence of the nucleoside analogue 5-fluorouracil (5-FU). We found that 5-FU was unable to trigger population extinction for the range of conce…
Delayed lysis confers resistance to the nucleoside analogue 5-fluorouracil and alleviates mutation accumulation in the single-stranded DNA bacterioph…
2014
ABSTRACT Rates of spontaneous mutation determine viral fitness and adaptability. In RNA viruses, treatment with mutagenic nucleoside analogues selects for polymerase variants with increased fidelity, showing that viral mutation rates can be adjusted in response to imposed selective pressures. However, this type of resistance is not possible in viruses that do not encode their own polymerases, such as single-stranded DNA viruses. We previously showed that serial passaging of bacteriophage ϕX174 in the presence of the nucleoside analogue 5-fluorouracil (5-FU) favored substitutions in the lysis protein E (P. Domingo-Calap, M. Pereira-Gomez, and R. Sanjuán, J. Virol. 86: 9640–9646, 2012, doi:10…
Correlation between mutation rate and genome size in riboviruses: mutation rate of bacteriophage Qβ.
2013
Abstract Genome sizes and mutation rates covary across all domains of life. In unicellular organisms and DNA viruses, they show an inverse relationship known as Drake’s rule. However, it is still unclear whether a similar relationship exists between genome sizes and mutation rates in RNA genomes. Coronaviruses, the RNA viruses with the largest genomes (∼30 kb), encode a proofreading 3′ exonuclease that allows them to increase replication fidelity. However, it is unknown whether, conversely, the RNA viruses with the smallest genomes tend to show particularly high mutation rates. To test this, we measured the mutation rate of bacteriophage Qβ, a 4.2-kb levivirus. Amber reversion-based Luria–D…
Variability in the mutation rates of RNA viruses
2014
ABSTRACT: It is well established that RNA viruses show extremely high mutation rates, but less attention has been paid to the fact that their mutation rates also vary strongly, from 10-6 to 10-4 substitutions per nucleotide per cell infection. The causes explaining this variability are still poorly understood, but candidate factors are the viral genome size and polarity, host-specific gene expression patterns, or the intracellular environment. Differences between animal and plant viruses, or between arthropod-borne and directly transmitted viruses have also been postulated. Finally, RNA viruses may be able to regulate the rate at which new mutations spread in the population by modifying f…
Effect of mismatch repair on the mutation rate of bacteriophage ϕX174
2015
Viral mutation rates vary widely in nature, yet the mechanistic and evolutionary determinants of this variability remain unclear. Small DNA viruses mutate orders of magnitude faster than their hosts despite using host-encoded polymerases for replication, which suggests these viruses may avoid post-replicative repair. Supporting this, the genome of bacteriophage ϕX174 is completely devoid of GATC sequence motifs, which are required for methyl-directed mismatch repair in Escherichia coli . Here, we show that restoration of the randomly expected number of GATC sites leads to an eightfold reduction in the rate of spontaneous mutation of the phage, without severely impairing its replicative capa…
The external domains of the HIV-1 envelope are a mutational cold spot
2015
In RNA viruses, mutations occur fast and have large fitness effects. While this affords remarkable adaptability, it can also endanger viral survival due to the accumulation of deleterious mutations. How RNA viruses reconcile these two opposed facets of mutation is still unknown. Here we show that, in human immunodeficiency virus (HIV-1), spontaneous mutations are not randomly located along the viral genome. We find that the viral mutation rate experiences a threefold reduction in the region encoding the most external domains of the viral envelope, which are strongly targeted by neutralizing antibodies. This contrasts with the hypermutation mechanisms deployed by other, more slowly mutating …
Variation in RNA virus mutation rates across host cells.
2014
It is well established that RNA viruses exhibit higher rates of spontaneous mutation than DNA viruses and microorganisms. However, their mutation rates vary amply, from 10−6 to 10−4 substitutions per nucleotide per round of copying (s/n/r) and the causes of this variability remain poorly understood. In addition to differences in intrinsic fidelity or error correction capability, viral mutation rates may be dependent on host factors. Here, we assessed the effect of the cellular environment on the rate of spontaneous mutation of the vesicular stomatitis virus (VSV), which has a broad host range and cell tropism. Luria-Delbrück fluctuation tests and sequencing showed that VSV mutated similarly…
Report of the IVth Workshop of the Spanish National Network on Mycotoxins and Toxigenic Fungi and Their Decontamination Processes (MICOFOOD), Held in…
2019
Ensiling is a practice commonly employed worldwide to preserve different kinds of crops for long periods of storage with similar nutritional values to the fresh materials. Since silages are one of the major components of the ruminant diet, these materials represent a potential source of mycotoxins as a consequence of the growth of filamentous fungi. The aim of this study was to analyse the presence of aflatoxins and Fusarium mycotoxins in different types of silages (maize, grass, alfalfa, sugar beet pulp, immature corn and ryegrass) collected in dairy farms located in four Spanish regions. Fungal populations, lactic acid bacteria, pH and water activity of the samples were also evaluated. Pe…
Expression of Drosophila Cabut during early embryogenesis, dorsal closure and nervous system development.
2010
cabut (cbt) encodes a transcription factor involved in Drosophila dorsal closure (DC), and it is expressed in embryonic epithelial sheets and yolk cell during this process upon activation of the Jun N-terminal kinase (JNK) signaling pathway. Additional studies suggest that cbt may have a role in multiple developmental processes. To analyze Cbt localization through embryogenesis, we generated a Cbt specific antibody that has allowed detecting new Cbt expression patterns. Immunohistochemical analyses on syncytial embryos and S2 cells reveal that Cbt is localized on the surface of mitotic chromosomes at all mitotic phases. During DC, Cbt is expressed in the yolk cell, in epidermal cells and in…
Assessment of Toxic Effects of Ochratoxin A in Human Embryonic Stem Cells
2019
Ochratoxin A (OTA) is a mycotoxin produced by different Aspergillus and Penicillium species, and it is considered a common contaminant in food and animal feed worldwide. On the other hand, human embryonic stem cells (hESCs) have been suggested as a valuable model for evaluating drug embryotoxicity. In this study, we have evaluated potentially toxic effects of OTA in hESCs. By using in vitro culture techniques, specific cellular markers, and molecular biology procedures, we found that OTA produces mild cytotoxic effects in hESCs by inhibiting cell attachment, survival, and proliferation in a dose-dependent manner. Thus, we suggest that hESCs provide a valuable human and cellular model for to…