Biomedical subjects

Juana Díez

Publications and source records attributed to Juana Díez.

5 recordsLinked to original sources

PubMed2006

Saccharomyces cerevisiae: a useful model host to study fundamental biology of viral replication.

Understanding the fundamental steps of virus life cycles including virus-host interactions is essential for the design of effective antiviral strategies. Such understanding has been deferred by the complexity of higher eukaryotic host organisms. To circumvent experimental difficulties associated with this, systems were developed to replicate viruses in the yeast Saccharomyces cerevisiae. The systems include viruses with RNA and DNA genomes that infect plants, animals and humans. By using the powerful methodologies available for yeast genetic analysis, fundamental processes occurring during virus replication have been brought to light. Here, we review the different viruses able to direct replication and gene expression in yeast and discuss their main contributions in the understanding of virus biology.

Animals↗

PubMed2006

Host deadenylation-dependent mRNA decapping factors are required for a key step in brome mosaic virus RNA replication.

The genomes of positive-strand RNA [+RNA] viruses perform two mutually exclusive functions: they act as mRNAs for the translation of viral proteins and as templates for viral replication. A universal key step in the replication of +RNA viruses is the coordinated transition of the RNA genome from the cellular translation machinery to the viral replication complex. While host factors are involved in this step, their nature is largely unknown. By using the ability of the higher eukaryotic +RNA virus brome mosaic virus (BMV) to replicate in yeast, we previously showed that the host Lsm1p protein is required for efficient recruitment of BMV RNA from translation to replication. Here we show that in addition to Lsm1p, all tested components of the Lsm1p-7p/Pat1p/Dhh1p decapping activator complex, which functions in deadenylation-dependent decapping of cellular mRNAs, are required for BMV RNA recruitment for RNA replication. In contrast, other proteins of the decapping machinery, such as Edc1p and Edc2p from the deadenylation-dependent decapping pathway and Upf1p, Upf2p, and Upf3p from the deadenylation-independent decapping pathway, had no significant effects. The dependence of BMV RNA recruitment on the Lsm1p-7p/Pat1p/Dhh1p complex was linked exclusively to the 3' noncoding region of the BMV RNA. Collectively, our results suggest that the Lsm1p-7p/Pat1p/Dhh1p complex that transfers cellular mRNAs from translation to degradation might act as a key regulator in the switch from BMV RNA translation to replication.

Adenosine Monophosphate↗

PubMed2005

Information catastrophe in RNA viruses through replication thresholds.

RNA viruses are known to replicate at very high mutation rates. These rates are actually known to be close to their so-called error threshold. This threshold is in fact a critical point beyond which genetic information is lost through a so-called error catastrophe. However, the transition from a stable quasispecies to genetic drift and loss of information can also occur by crossing replication thresholds, below some replication rates, the viral population is suddenly unable to survive. Available data from hepatitis C virus population analysis [Mas, A., Ulloa, E., Bruguera, M., Furcić, I., Garriga, D., Fábregas, S., Andreu, D., Saiz, J.C., Díez, J., 2004. Hepatitis C virus population analysis of a single-source nosocomial outbreak reveals an inverse correlation between viral load and quasispecies complexity. J. Gen. Virol. 85, 3619-3626] can be interpreted through this theoretical view, providing evidence for such a replication threshold. Here a simple model is used in order to provide evidence for such a phenomenon, consistent with available data.

Cross Infection↗

PubMed2004

Hepatitis C virus population analysis of a single-source nosocomial outbreak reveals an inverse correlation between viral load and quasispecies complexity.

The features of Hepatitis C virus (HCV) quasispecies within an envelope segment including the hypervariable region 1 were analysed at an early time point post-infection in seven patients that acquired HCV from a single common donor during a nosocomial outbreak. The grouping of patients according to viral load was reflected in the structure of the quasispecies. A higher viral load correlated with the presence of a predominant HCV genome and a corresponding lower quasispecies complexity. The quasispecies complexity itself was not correlated with HCV clearance or persistence. Thus, the relationship between an intrapatient HCV quasispecies and the clinical outcome of an HCV infection is more complex than previously anticipated.

Amino Acid Sequence↗

PubMed2003

Mutation of host DnaJ homolog inhibits brome mosaic virus negative-strand RNA synthesis.

The replication of positive-strand RNA viruses involves not only viral proteins but also multiple cellular proteins and intracellular membranes. In both plant cells and the yeast Saccharomyces cerevisiae, brome mosaic virus (BMV), a member of the alphavirus-like superfamily, replicates its RNA in endoplasmic reticulum (ER)-associated complexes containing viral 1a and 2a proteins. Prior to negative-strand RNA synthesis, 1a localizes to ER membranes and recruits both positive-strand BMV RNA templates and the polymerase-like 2a protein to ER membranes. Here, we show that BMV RNA replication in S. cerevisiae is markedly inhibited by a mutation in the host YDJ1 gene, which encodes a chaperone Ydj1p related to Escherichia coli DnaJ. In the ydj1 mutant, negative-strand RNA accumulation was inhibited even though 1a protein associated with membranes and the positive-strand RNA3 replication template and 2a protein were recruited to membranes as in wild-type cells. In addition, we found that in ydj1 mutant cells but not wild-type cells, a fraction of 2a protein accumulated in a membrane-free but insoluble, rapidly sedimenting form. These and other results show that Ydj1p is involved in forming BMV replication complexes active in negative-strand RNA synthesis and suggest that a chaperone system involving Ydj1p participates in 2a protein folding or assembly into the active replication complex.

Bromovirus↗